prop help 750 westcoaster 225 yam 4 str
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URL: https://www.fishing.net.nz/forum/forum_posts.asp?TID=74052
Printed Date: 10 Jun 2026 at 11:22am
Topic: prop help 750 westcoaster 225 yam 4 str
Posted By: Down Time
Subject: prop help 750 westcoaster 225 yam 4 str
Date Posted: 02 Jan 2012 at 9:23pm
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Can any one help me or tell me who might?
I am currently running a 19x15 and a quarter prop cruising at 18-19 knots at 4000rpm using 40 lph, flat out at 32 knots 5200 rpm using 72 lph.
The boat weighs approx 2750kg fueled and loaded , was hoping for a cruise of around 22-24 knots 35 lph.
any advice much apreciated
Cheers Tony
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Replies:
Posted By: Tagit
Date Posted: 02 Jan 2012 at 9:49pm
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Figures sound bad. At 4000rpm, correctly propped you should be closer to 33lph than 40lph. Currently you appear to be a bit over propped based on your fuel burn. A WOT of 5200rpm tends to confirm this. Having said all that, your speeds also seem low for that hp on a 7.5m boat. I don't know what engine you have, so can't check the gear ratio, but if it is a Yamaha F225 with a 2:00:1 box then your 'no prop-slip' speed at 4000rpm would be ~31knts (might want to check my maths). At 19knts you have ~40% slip which says that something is badly wrong. Assuming that the hull is clean etc, my first check would be engine height. A too low engine could explain most of what you are experiencing. I doubt that the problem is as simple as having the wrong prop. The other simple possibility is that your prop is damaged in some way. After that the reasons get harder to work out.
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Posted By: Down Time
Date Posted: 02 Jan 2012 at 10:39pm
| Hi tagit Yes engine is yamaha f225 05 model couldnt tell you Gb ratio tho. hull is clean and engine looks too be at right height. Saying that tho engine is on a pod that extends 320 mm and using a spirit level on the cavatation plate level with the hull shows the cav plate too be 25 mm higher than the bottom of the v. engine currently sits on second hole down from the top. so room to move either way. |
Posted By: andrem
Date Posted: 02 Jan 2012 at 11:35pm
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19 to big for that engine boat IMO. I have a 7.5m billfisher with an f200 on it. Had a play with a few different props including a 19 which gave similar figures to what. You are stating in your first post ( maybe a little better) currently settled on an 18 4 blade prop which will see me get 5900rpm at wot and cruise at 22knts doing just under 4000 with fuel burn just under 30 Lph. Have a chat to the guys at propellor services they are pretty helpful. ------------- Rehab |
Posted By: Tagit
Date Posted: 03 Jan 2012 at 9:54am
Engine height sounds like it should be close. Has the boat always performed like this? Based on similar sized boat/engine combos I would have thought a cruise around 22/23, and your fuel burn at 4000 should be around that 33lph figure with that engine. Are you in Auckland?
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Down Time wrote:Posted By: Down Time
Date Posted: 03 Jan 2012 at 10:21am
| Yes south auckland, down whitianga way at till next week tho. would be happier with those figures. Had f200 on my last boat 650 sea nymph walkaround with same size prop, was well suited. Which makes me think its too big for this one?? |
Posted By: Down Time
Date Posted: 03 Jan 2012 at 11:49am
| Thanks Adrem, Good to know. will have a look around for some thing close , its a start anyway. |
Posted By: Bounty Hunter
Date Posted: 03 Jan 2012 at 12:05pm
tagit - can you provide some more info about calculating engine/boatspeed though gearbox and propeller measurements/efficiency perhaps a link to something? ------------- No disintegrations! |
Posted By: Big -Dave
Date Posted: 03 Jan 2012 at 2:15pm
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engine revs divided by gearbox ratio gives you prop revs ie 500rpm at 2 to 1 ratio is 2500rpm at the prop. 19 inch prop travels 19 inches per rev, 19 x2500= 47500 inches traveled per minute Convert inches to meters by dividing 47500 by 39.5 and you get approx 1202 m traveled in that minute. Multiply by 60 and you get 72120 m, or 72 kmh. Props all have a percentage of slip, depending on load and prop design, so say at 10 %slip, 72 x.9 is about 65kmh realistic speed. ------------- you can't fix an idiot with duct tape, but it does muffle them for a while... |
Posted By: Moki Marko
Date Posted: 03 Jan 2012 at 3:35pm
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I'm assuming by 19x15 and a quarter - you mean a 19"pitch and 15 and a 1/4" diameter - (wouldnt fit the other way around anyway) these numbers mean a big prop, is it a Mirage? A big diameter prop, moves a lot of water with minimal slip, can be a bit slow off the mark, thats no probs on a fishing rig but it isn't a 'top speed' prop. You need lots of torque to turn it too and a 225 yam is a bit anemic in the torque dept. The 19" pitch is also big, too big (we say big but we should say coarse, we're talking about the angle of the blades not the size of the prop) for the weight of your boat- but as Tagit says at 4000rpm with a 19" prop you should be cruising around 25 - 27knots - could it be that you have read the numbers wrong and you have a 15" pitch? - and 14" diameter is the norm |
Posted By: Tagit
Date Posted: 03 Jan 2012 at 8:47pm
| MM - the Yamaha website shows mainly 15" diameter props for the F225 if using the 'standard' props. As you say though, the F225 is an anemic 225 compared to some other brands. I am struggling to work out the high slip figure though as even when turning the rpm's, DT's boat isn't making the speed. |
Posted By: Tagit
Date Posted: 03 Jan 2012 at 8:47pm
| BH - Shrekky saved me the trouble of tying all that. Thanks Shrekky. |
Posted By: bluesignature
Date Posted: 04 Jan 2012 at 7:23am
| there is one of theese boats with the same motor on trademe the dude has done 650hours in it you could give him a ring to see how he has it set up (0274898628). there is no guarantee the prop is actually 19inch you could get the pitch checked i had a brand new prop that was supposed to be 17inch when checked was 17.7 inch so closer to 18.you could get it checked you could get an inch taken off the pitch cheaper than buying a new prop. |
Posted By: blackboat
Date Posted: 04 Jan 2012 at 7:52am
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yip thats Lone stars boat here he does some big trips so he will know all the figures etc think hes running a 19 ------------- http://www.legasea.co.nz" rel="nofollow"> 
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Posted By: Moki Marko
Date Posted: 04 Jan 2012 at 8:43am
SO the factory props are 15" dia - and a 2:00-1 gearbox reduction - thats a lower gear than the honda or mercs that I have run, so makes sense that it would turn a bigger diameter and coarser pitch prop - a 19inch may not be too far out of the ballpark, well, close enough to get reasonable numbers for evaluation - so yes, a bit strange - need to try a few different props DT. |
Posted By: Down Time
Date Posted: 04 Jan 2012 at 5:54pm
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Appreciate all the help guys, Did consider enquiring about the prop on the wc on trade me, but that
one is an earlyer shape hull could be different again??
have since found another one the same too check out when it suits. Was lucky enough run into a good bloke in whiti yesterday who let me try his 17x15 and a half results were alot better could reach 5600rpm at 36kn, cruise at 24kn 4000rpm and 36lph. This may be as good as it gets??
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Posted By: Tagit
Date Posted: 04 Jan 2012 at 6:40pm
| Those figures sound about what you would expect DT. Sounds like a 16" pitch would be ideal as I would prefer to be hitting 5800+, but at 5600 you are probably not doing any harm. What I am surprised about is how poor the original prop was by comparison. Is it in good nick? What type is the original prop, and what type prop did you try today? Some rigs go much better with different prop types even though they may notionally be the same pitch and diameter. |
Posted By: Moki Marko
Date Posted: 04 Jan 2012 at 6:53pm
| agree - again, the yam 225 is a short stroke rever, doesn't produce max power untill its almost hitting the rev limiter. ie even at 5600rpm it's still not producing 225hp. SO don't be afraid to rev it's nuts off, you're already suggesting a 4000rpm cruise, thats a good minimum. As Tagit says to get the max out of that motor a 16" prop is probably going to be the best option |
Posted By: Down Time
Date Posted: 04 Jan 2012 at 9:12pm
| my thought as well Really keen too try a 16. Tagit the prop i tried was a yamaha saltwater series 15 1/2x 17. also when got the boat the skeg tip was broken paint scraped off etc, but prop in exc cond which made me wonder weither they hed slapped this one on for a sale??unsure of brand on existing no visable markings. |
Posted By: Big -Dave
Date Posted: 05 Jan 2012 at 8:49am
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factory props can be next to useless at times. Yamaha ones are some of the worst in my opinion. I swapped the solas prop on my honda for a mercury vengeance prop, unbelievable difference. Many Yamaha and omc owners end up with mercury/quicksilver props on them. ------------- you can't fix an idiot with duct tape, but it does muffle them for a while... |
Posted By: Down Time
Date Posted: 05 Jan 2012 at 9:37am
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your 3rd person too tell me that shrekky, hardcase that would have thought yamaha would be on top of that by now! on a mission today too find something closer too 16 for a trial. |
Posted By: Bounty Hunter
Date Posted: 05 Jan 2012 at 8:29pm
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what s the go with purchasing propellers? would one expect a 'try before you buy' from a retailer ? - provided it was returned in mint condition? ------------- No disintegrations! |
Posted By: Big -Dave
Date Posted: 05 Jan 2012 at 10:34pm
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A mate and I once trialled a boat, had a 150 yammie on it, 6.8 m senator. We were told the guy was trading it as he had used it for picking up cray pots. I reckon the yammie prop was ruining the boat, it had next to no reverse thrust, it bordered on dangerous. He brought the same boat with a 175 verado on it, totally different boat. It actually goes backwards properly when you need it to. ------------- you can't fix an idiot with duct tape, but it does muffle them for a while... |
Posted By: Big -Dave
Date Posted: 05 Jan 2012 at 10:36pm
I have heard Yamaha agents are tight as with their props. you can only ask around. FInd a Merc dealer, they have a huge range of props and the appropriate hub kits. Go ask.. ------------- you can't fix an idiot with duct tape, but it does muffle them for a while... |
Posted By: Tagit
Date Posted: 06 Jan 2012 at 10:48am
| There is a guy in Helensville (I think) who owns/runs The Prop Shop. I think it might also be known as "Nauti bits" or something similar. You could try calling him and see if you can do a deal to try a prop or two if he has the ones you need. |
Posted By: Big -Dave
Date Posted: 07 Jan 2012 at 12:14pm
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Nauti bits?, just what sort of props are we talking about?
------------- you can't fix an idiot with duct tape, but it does muffle them for a while... |
Posted By: Reel Crusader
Date Posted: 19 May 2012 at 10:46am
| Ahh - got it. Thanks Shrekky - after much head scratching I worked out there's a small error in the first calc - 500RPM divided by 2:1 gearbox ratio is 250 - not 2500....... flowing this correction through the rest of the calcs gets a potential speed of 7.22 KPH (more realistic for 500RPM). Just thought I'd add this if anyone else is workng through this thread as there's some great advice in it. |
Posted By: Space Boy
Date Posted: 19 May 2012 at 11:38am
17 pitch vengance merc prop is what you want 5600 rpm is fine.
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Posted By: Down Time
Date Posted: 19 May 2012 at 3:14pm
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In the end after endless testing, Including a 17 inch mirage, and 17 vensura both merc props off another 750/225fs(earlier model different hull shape) Which didnt perform on mine. I settled with a baypro 3 15 inch 4 blade from propeller services who were exellent to deal with. With this prop it will cruise at 25-26 kt at 4600-4700 using 35-37 lph. taken a while to get used to those revs but the engine loves it, any slower it starts to drag its arse. Troll 7.5-8.5 kt at 2000-2200 using 8-12 Lph. Im happy with those figures for the size and weight we are pushing.
Thanks for all the feed back guys
Cheers Tony
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Posted By: Tagit
Date Posted: 19 May 2012 at 3:54pm
Those are pretty good numbers now Tony. Close to what I estimated when you first posted (22knts @ 4000rpm @ 33lph
 ), but you are choosing to rev a bit higher to get the extra speed. Fuel burn suggest you are now just very slightly underloaded at cruise (should be ~38lph), so that would explain why your speed in probably off by a knot or two at 4600, but I wouldn't worry about that as you are so close to optimised now that any further gains are going to be marginal vs the cost involved. Good result and thanks for letting us know how you got on. |
Posted By: Reel Crusader
Date Posted: 19 May 2012 at 3:56pm
Was that the 14 1/4" x 15" Down Time? I was chatting with a guy from Propeller Services at the Boat Show and he also pointed me towards this prop for my boat (7.5m Whitepointer running Etec 225) to get better fuel economy, especially when trolling. He indicated an improvement of 15% at least could be anticipated, presumably from more bite/less slippage(???) I have done the calcs on current setup (15"x16" 3 blade) based on the posts in this thread and was rather shocked at the results - slippage up around 40-45% at trolling speeds! (but down to 11.5% at 22knt cruise) These are all "fair weather" results but of course that all goes out the window after a summer like we've just had when you're trolling in rough seas and grinding it home at 15knts (which seems to be an especially thirsty speed on my boat!). So the thinking is a 4 blade with more bite will particularly improve fuel economy (and handling) on those "not so flash" days when the fuel consumption goes through the roof. Whadoufink? Was that your experience with the Baypro re overall handling and better fuel economy at lower speeds?
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Posted By: Tagit
Date Posted: 19 May 2012 at 4:22pm
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RC - more difficult handling in heavy weather is often a function of being at the lower end of the HP range for a hull. If this is a real issue, you might want to consider going slightly 'under propped'. This will help with the engine 'stalling' and 'surging' in heavy weather if this is the problem. Like Tony you will probably want to cruise at higher rpm's but within reason this is probably an acceptable solution. Slippage at trolling speeds is probably as much to do with the hull as the prop. The 'hull speed' for your boat is probably 6 - 6.5knts. Anything above this and below a stable planing speed is a bit like dragging a bucket behind the boat as far as engine loading and prop slip goes. If you did a quick graph of fuel burn and hence kmpl between 5 knts and 9 knts at 0.5knt intervals you will see how much extra 'load' you are carrying once you get to ~7knts. If you are getting 40%+ prop slip when trolling I expect you are trolling above 6.5knts? The 4 blade may well help this a bit, but the biggest change will come from setting your gear so you can troll a little slower.
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Posted By: tugboat
Date Posted: 19 May 2012 at 6:34pm
| Whats billfish running on his dave, hasnt he got the same motor?? |
Posted By: Sambosi
Date Posted: 19 May 2012 at 7:11pm
What model honda and rig have you got and what improvements did you get shrek out of interest. I am pretty happy with the economy of my 150 with the solas but am interested if it could be improved.
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Posted By: Reel Crusader
Date Posted: 19 May 2012 at 11:45pm
Thanks Tagit - you've nailed it and excellent advice! The Etec has an "economy mode" when running <1800 RPM which is just under 7knts for me. I've done that fuel graph and it gets ugly from around 7 knts through to mid-high teens when it gets up on the plane (and calculated slippage drps down to something more acceptable). That "dragging a bucket" sensation is bang on and good advice to save the $$$ on a new prop (around $900 with "boat show discount") and just target trolling at a slightly lower speed. I'm newish to game fishing (have moved north from the southern flat lands) and been trageting the "recommended" 7 knts troll speed but noticed that's right where the lph starts getting vey unecnomical (and more engine noise), especially in rougher seas. Going a bit slower won't hurt, certanly using Mangre's SST-based info helps put you in the zone which makes trolling speed (i.e. covering territory) a lower priority than just targeting the right zone. That said, looks like you can get a Baypro III from the US for around US$300 (+ freight etc.) so might be worth a look for more rough-sea bite/steerage and always good to carry a spare prop, no?
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Posted By: Tagit
Date Posted: 20 May 2012 at 9:57am
| I don't know the Baypro props so can't comment on them. Trolling slower will mean having a good look at your lure selection. You may need to increase the height you troll lures from, or change to a more active lure head style as some of the more popular lures may get a bit lazy once under 7 knts. Just experiment a little until you have a spread that is working well at the speed you are economically trolling at. The other thing that will save you heaps on fuel is learning to live bait. Get that sorted and you can get your fuel bill for a mixed day of trolling and livebaiting way down. |
Posted By: Busted!
Date Posted: 20 May 2012 at 11:15am
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Thats a lot of weight for that prop and motor and hull combination.
Try offloading anything that isn't nailed down and running light fuel (as close to 'light ship' as you can get and still have the required safety stuff) and see what your results are then.
If they get better you could try a thinner prop to take the laod off the engine, or keep the same prop and hang a bigger donkey off the back.
Most of the time, manufacturers spec their boats to perform with xxx engine at xxx weight but once the owners get on board with 2 tonnes of 'essential crap' the boat is much heavier and cannot perform...
An extra 100Hp and 1" in each prop made a hughe difference to my boat considering we normally run at full load as a charter vessel.
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Posted By: Down Time
Date Posted: 20 May 2012 at 9:05pm
| Yes thats the prop i have RC, I didnt get to i nvolved in the calculation side of things it started to do my head in! I left that to steve at propeller services. Would definatly be worth a shot as it seems to be a popular one for boats this size. As for the rough stuff it grinds away at 18-20kt around 4000 i think?? with no stalling or surging cant recall fuel burn, but wasnt excessive. Down side, laking slightly in reverse thrust. other than that perfect. Hope this helps Cheers Tony |
Posted By: ReelAppealLures
Date Posted: 21 May 2012 at 11:56pm
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How would you apply the prop calculation formula to a DuoProp? I want to run some figures, but don't know if this applies or you do something different...  ------------- http://www.facebook.com/pages/Reel-Appeal-Lures/300309486704362 |
Posted By: Tagit
Date Posted: 22 May 2012 at 12:24am
| Sam - the Volvo Duoprops (is this what you have?) don't have a published equivalent pitch that I know of. The best I have found is that you gain/lose approx 200 - 250rpms per number change (i.e. C2 to C3 etc). I believe that the smaller number (i.e. C2) is the smaller prop. Doing prop slip calcs in the way we did earlier in this thread would probably require a Volvo specific prop slip calculator, and I don't know of one. If you do find any more info, please share it with us. If on the other hand you have a bravo 3 drive, I have heard that the props are stamped with an 'effective pitch' number that you could do calcs based on. Not sure about this, but is what I was told. |
Posted By: Big -Dave
Date Posted: 23 May 2012 at 12:53pm
Motor is 130hp, 2000 model, on a Figlass Viscount, in the water with ger on about 2 tonne. The prop increased my out of the hole performance considerably, and I was able to achieve a better top speed while fully loaded.(kids and crap) It is also very difficult to make it cavitate, and reverse thrust is much better, it will drag the stern under.. |
Posted By: wopass
Date Posted: 27 May 2014 at 12:04pm
hey chaps, thought i would drag up this thread instead of starting another... 
new tub (to me)
2002 7.1 westcoaster hard top with a 1200hr
 2002 Yam F225 on its bum. (just did big service and exhaust corrosion problem was there so its all good now!)looking for the best prop for it as the one it has is a bit on the large side, merc vengeance 19p
solas titan4? have heard good things but dont know enough about the science behind props so just gonna ask for advice from people who do know
 cheers
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Posted By: Tagit
Date Posted: 27 May 2014 at 12:14pm
| Where about are you? I might have a 17 that you can try (we have a couple of spare props so need to check what they are). What WOT rpm's are you getting? |
Posted By: wopass
Date Posted: 27 May 2014 at 1:09pm
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WOT is to be confirmed this week i hope... as when we got it, the motor had a siezed gear shift bush so was pulling up a neutral position rpm limit of 4300rpm and only managed to get that to clear once and i think it only pulled just over 5k rpm nuts out so pretty sure its over propped so will have to confirm yet. boats in Taupo at the mo and have a 17p yam prop borrowed off the good lads at Tristram in Hamtown who do all my work. will report on WOT with both props later in the week.
would be keen to find specs for the new rig of weights and hull deg etc etc but theres nothing on the net and i cant find any contact for westcoaster boats anywhere!... maybe im looking in the wrong places?
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Posted By: Tagit
Date Posted: 27 May 2014 at 1:35pm
| If you are just over 5k with the 19 when loaded, the 17 should get you reasonably close. What do you mean by a "neutral position rpm limit of 4300rpm"? Haven't come across that one before. |
Posted By: wopass
Date Posted: 27 May 2014 at 2:19pm
| when in gear and trying to go full noise the motor was limiting to 4300rpm because it was seeing it still in neutral because of the very hard to shift siezed bushes on the shift shaft. like if your in neutral and crank the hand throttle wide open it will only pull 4300rpm |
Posted By: Tagit
Date Posted: 27 May 2014 at 2:51pm
| Thanks for that. Understand what you mean now. |
Posted By: wopass
Date Posted: 29 May 2014 at 6:21pm
| Ok so went for a skid in the tub and with the 19p vengeance it pulls 36knots trimmed to pull max rpm of 5900, trimmed full nose down it's pulling 5400rpm. Pulled the prop off and slapped the yam 17p on and it pulls 34/35knots and pulls 6000rpm easy when trimmed up and full nose down it rolled 5600-5700rpm and felt much more lively. So, vengeance 19p runs in the rev range just but feels better with the 17p so will be re propping. |
Posted By: wopass
Date Posted: 29 May 2014 at 8:07pm
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So what I forgot to add was... With so many options out there which is actually best? After a lot of reading posts by FD I thought I better add, it has a perma trim and is bolted on the bottom holes. Thinking a solas Titan 4 might be a good choice as they provide better lift and lower plane speeds etc? Any advice, pros and cons welcome |