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Ramco 5.5m Motor Query...

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    Posted: 08 Sep 2020 at 6:21pm
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Evening Gang,

Currently have a 2008 Merc 60 Bigfoot 4 Stroke but the whole trim system is corroded and given up the ghost.

The boat says it is rated to 75hp, but as is an older boat, not sure about buying a brand new motor for it. ideallly get something second hand at this stage.

The problem is - 75hp on TM etc are't hugely common. I would like to stay 4 Stroke otherwise I feel i'm going backwards to 2 stroke.

The 60hp is probably slightly under-powered as is noticable getting on the plane with 3+ people and a heavy chillin bin + gear.

Any thoughts options, or if anyone knows of anyone/ place selling a second hand 75hp 4 stroke, this would be much appreciated.

Cheers! Jason Big smile
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Post Options Post Options   Likes (0) Likes(0)   Quote krow Quote  Post ReplyReply Direct Link To This Post Posted: 08 Sep 2020 at 8:30pm
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You also might find the extra weight of the 75 4/ upsets the ride too.Though maybe do some homework the new(er) 75's might be similar weight to your older 60. On my Dominator I replaced the merc 75 2/ with a 60 suki 4/ and it performed very well. Even better when I put in an under floor to lower weight and move weight forward. Like you say maybe a little under powered but 1/2d my fuel bill. Yes I'd avoid putting new motor on her as won't get that back on resale. 
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Post Options Post Options   Likes (1) Likes(1)   Quote The Tamure Kid Quote  Post ReplyReply Direct Link To This Post Posted: 08 Sep 2020 at 8:53pm
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When Steps has finished his evening cocoa, hopefully he'll open up his treasure trove of data and give you the power requirements.
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Post Options Post Options   Likes (0) Likes(0)   Quote May Quote  Post ReplyReply Direct Link To This Post Posted: 09 Sep 2020 at 7:28am
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Thanks for this mate. Yer I’d be happy with a 60. The Bigfoot makes it easier out of the hole but wouldn’t hurt to get a stainless prop also I guess.
What did you use for underfloor fuel? Was it an off the shelf adaption from something or custom boxing? Would you have a rough cost for that?
That’s another thing I was thinking about in terms of weight - could free up a little space at the back with fuel tanks etc
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Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 09 Sep 2020 at 9:50am
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When Steps has finished his evening cocoa, hopefully he'll open up his treasure trove of data and give you the power requirements.

Nah , busy shucking scallops from yesterdays haul.. All very fat, yet 4 days ago where rather mixed.

I dont have the older ramco 5.5m on in my data base so require bit info.

Normal load, with gear what would you estimate the total gross weight on the water?
With current engine, normal loaded what was the WoT speed?
Did you have permatrim on the cavitation plate?

Top speed only matter as much as the top speed of a tractor or the wifes shopping basket car.. In saying that it is a very reliable guide line to how a planning hull performs in chop, wakes, bars and general economy and safety.
 The difference between a min and well powered is like having 2 completey different boats.
 General rule of thumb for around  5.5m hull general use boat,  WoT
 Well powered WoT around 42 /43 mph
 Over powered 48/52 mph
Min powered around 36 mph.

Well and over powered, when in chop can set the throttle . stay on the plane without working it or fall off the plane.

From other similar boats  I guesstimate 3 guys ave say 85kg, fuel gear etc gross weight on water would be around the 1000 to 1100 kg.
 IF the guesstimate is ball park right with 60hp 4S you would have a WoT about 32 mph
That would make well powered for a general use boat around 1100 kg normal load around the 100/ 115 hp.

 I do not know the manufactures actual specs.. re powering to the max in effect gets you a totally new far improved performing hull in chop .. well across the board.

And no issues when comes to get on the plane.
 If a boat has issues getting up, then either the engine is set too low, wrong prop  or just doesnt have the low rpm power to get it up over the bow wave well.

Weight.. as engine weight increases with power, it follows that when moving the stern still lifts up fine. You will sit a little lower at the stern .. couple inches..at anchor.
 

 Stainless prop..?
 The difference is where the load on the prop (big heavy boat) and the power at the prop ( lot of power at that rpms) is able to twist the alloy blades enough to effect the slip and pitch of the prop specs.

Also is often go into shallow water, around rocks to clip the prop, that puts huge loads on gearbox ( $2.5/ 3.5 K) and power head with a stainless prop. An alloy absorbs far more of the shock and will bend break.

So when does that load come into effect? Starts with about a 1400kg boat, not enough to make any difference  and  starts to be noticeable when get up around 1800kg ( 6m +) at cruise and above.

 Im running a 5.5m boat around 1200kg  bitover powered with 150hp and have a alloy prop... Yes when crunch the numbers above normal 32/ 34 mph cruise , its just starting to be just significant, and significant over 45 mph.. a speed that I very rarely use and if don only for short distance.

There is the sale a person propaganda world and the real would of practical application backed by science.

And very important.. you CAN NOT fix a min or ok powered boat by changing the prop. over propping may seem to help, but just loads up the powerhead to eventual slow death.



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Post Options Post Options   Likes (0) Likes(0)   Quote Catchelot Quote  Post ReplyReply Direct Link To This Post Posted: 09 Sep 2020 at 10:20am
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Originally posted by krow krow wrote:

You also might find the extra weight of the 75 4/ upsets the ride too.Though maybe do some homework the new(er) 75's might be similar weight to your older 60. On my Dominator I replaced the merc 75 2/ with a 60 suki 4/ and it performed very well. Even better when I put in an under floor to lower weight and move weight forward. Like you say maybe a little under powered but 1/2d my fuel bill. Yes I'd avoid putting new motor on her as won't get that back on resale. 

That Suzi 4/ was 70 hp mate, not a 60Ouch
"The sea, once it casts its spell, holds one in its net of wonder forever." - Jacques Cousteau
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Post Options Post Options   Likes (0) Likes(0)   Quote May Quote  Post ReplyReply Direct Link To This Post Posted: 09 Sep 2020 at 10:33am
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Wow - thanks for this Steps. Lots of info to process there.

Normal load, with gear what would you estimate the total gross weight on the water?
I am not 100%, but have been told by a few people that with full 25l and 40l totes with a chilli bin of bait and rods etc it would be approx. 750-800kg - add 85ish kg for 2 POB and you have say around 950kg odd.

With current engine, normal loaded what was the WoT speed?
WOT = Wide Open Throttle I assume? Using the situation above going out for a day of fishing in fairly calm seas  would be maxing out at around 26 or so knots fully trimmed up using a standard black composite merc prop (so slightly under at about 30mph?)

Did you have permatrim on the cavitation plate?
There is not cavitation plate on the motor.

I do also find that my boat is on the lighter side from what I have seen in other 5.5m options - just not a lot to it. They seem to be a bit more slender. This also makes them quite 'tippy' at rest. 
It moves around a little when going through chop, but the hull seems to perform fairly well.

I also had the height of the engine adjusted to try and get me out of the hole better as was really lagging prior. It is a lot better, but still feels a bit slow in the bum when taking off.

See photos - you will also see the faulty/ corroded trim system.






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Post Options Post Options   Likes (0) Likes(0)   Quote Schampy Quote  Post ReplyReply Direct Link To This Post Posted: 09 Sep 2020 at 4:55pm
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Always a tricky one. A new 75 is gonna be 15k  plus fitting. An yes they never seem to be many on TM.  Options are Go for a 70 yam..... prolly the cheapest.
75 Etec. basically rolling the dice there.  What about a 90 yam 2 stroke. At least the extra grunt will  help provide better fuel economy are lite weight and there seems to be a few around if you look. Or cheapest option is getting the ram replaced. Surely you would do that before you sold the engine anyways? 
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Post Options Post Options   Likes (0) Likes(0)   Quote Catchelot Quote  Post ReplyReply Direct Link To This Post Posted: 09 Sep 2020 at 5:04pm
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I cannot see a 90 2/ being more economical than the 75, you don't get extra grunt without burning more fuel mate.

I would be looking at 4 strokes if the weight factor and budget is ok.
"The sea, once it casts its spell, holds one in its net of wonder forever." - Jacques Cousteau
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Post Options Post Options   Likes (0) Likes(0)   Quote pjc Quote  Post ReplyReply Direct Link To This Post Posted: 09 Sep 2020 at 5:32pm
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If the existing motor is good why not replace the tilt/trim system?
She said you're deaf.No I have selective hearing.And thats when it started.
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Post Options Post Options   Likes (0) Likes(0)   Quote May Quote  Post ReplyReply Direct Link To This Post Posted: 09 Sep 2020 at 5:45pm
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Hi all,

The tilt system was going to be a good few grand to replace and was also told there are other bits and pieces that will need to be replaced a little further down the track that are starting to wear like a few of the control arms/ exhaust etc - apparently it looks like it wasn't treated well at the start of its life so therefore showing issues popping up now. Quite a bit of rusty/ corroded parts showing between motor and transom.
This was prior to me as I have cleaned it religiously as well as got a full service each year.

So - I didn't think it was worth chucking a bunch of money at an older motor that will just keep giving me grief.
Rather go and get a similar motor that is in better condition.

Do these issues seem normal for this year of motor or is it about right?

On my old smaller tinny, I had a 1999 60hp yammy 2 stroke and was a breeze compared to this motor. Was mint condition and had not wear on it.

Keen to hear your thoughts.

Jason
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Post Options Post Options   Likes (0) Likes(0)   Quote Rozboon Quote  Post ReplyReply Direct Link To This Post Posted: 09 Sep 2020 at 7:49pm
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It would be worthwhile finding out the weight of your existing outboard. Current manufacturers are all over the place, in terms of vastly different motors with the same rated power output, and there's a decent chance the crop of motors available when your boat was built looked a little different to what's out there today. I suspect 5hp extra isn't going to fold the boat in half, and it's not like you need to worry about a warranty.

There are lots of good motors in your ballpark - Yamaha and Suzuki 70s, Yamaha and Mercury 75 (both quite big motors, hence the weight question), Honda BF80. Just a matter of finding one that fits your budget as well.

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Post Options Post Options   Likes (0) Likes(0)   Quote krow Quote  Post ReplyReply Direct Link To This Post Posted: 09 Sep 2020 at 8:32pm
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Originally posted by Catchelot Catchelot wrote:

Originally posted by krow krow wrote:

You also might find the extra weight of the 75 4/ upsets the ride too.Though maybe do some homework the new(er) 75's might be similar weight to your older 60. On my Dominator I replaced the merc 75 2/ with a 60 suki 4/ and it performed very well. Even better when I put in an under floor to lower weight and move weight forward. Like you say maybe a little under powered but 1/2d my fuel bill. Yes I'd avoid putting new motor on her as won't get that back on resale. 

That Suzi 4/ was 70 hp mate, not a 60Ouch
Thats just funny I checked and yep I'm old Ouch
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Post Options Post Options   Likes (0) Likes(0)   Quote krow Quote  Post ReplyReply Direct Link To This Post Posted: 09 Sep 2020 at 8:36pm
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Originally posted by May May wrote:

Thanks for this mate. Yer I’d be happy with a 60. The Bigfoot makes it easier out of the hole but wouldn’t hurt to get a stainless prop also I guess.
What did you use for underfloor fuel? Was it an off the shelf adaption from something or custom boxing? Would you have a rough cost for that?
That’s another thing I was thinking about in terms of weight - could free up a little space at the back with fuel tanks etc
Underfloor was SS and I picked it up on trademe. Was off a 5m Ramo and just 60l. Made a difference though. I thought the ride was good but definitely improved with the underfloor. Was using it for game fishing so needed space as carrying too many tots.  
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Post Options Post Options   Likes (0) Likes(0)   Quote RC1 Quote  Post ReplyReply Direct Link To This Post Posted: 09 Sep 2020 at 10:08pm
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75hp Honda would be awesome to replace it with. Around 10K all up
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Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 10 Sep 2020 at 9:40am
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I recon you would be closer on weight than my estimate..
 Below I will give instructions as to how to weigh your single axle boat, on the trailer with bathroom scales in the drive

Weight: say around 950kg
WoT  30mph
60 hp.
 I would be looking at your engine height.. something be it the weight estimate or extra engine drag because lower is in effect.. assuming the engine is producing correct hp.
  or Either the estimate should be around 1100 kg

This would also effect your holeshot

Lets assume total gross weight on the water is 1000kg, little extra power will never go amiss, engine works lighter, leaner fuel, less rpms  and therefore less mixture(engine volume per distance = economy + hull performance.

To have WoT around 42 mph will require about 90hp @1000kg
If stay with merc 4S 2004+  correctly propped for the 2.33 gearbox and 5500 rpms Max WoT at normal load, correct slip @ WoT and about 4000 rpm cruise.
Will be about a 19 pitch prop..( final diameter established on sea trial but ball park would be 13 3/4 for starter)
WoT about 41.5 mph
 4000 rpm cruise  28/29 mph
And be able to go thru chop a little faster than currently able to, and considerably more comfortable..
No Im not a fan of crashing hulls thru chop.. too old for the BS now.

What is the manufactures hp rating for the hull?

Anyway how to weight your boat on the trailer in the drive with bathroom scales...
 Keep in mind about this size, weight on hitch at hitch height when loaded will or should be around 80kg
This is from an old physics/ maths class of mine around 50yrs ago.
Measurements/ weights must be as accurate as possible.


 Did you know you can weight the boat (only the boat)  on the trailer with bathroom scales?

 keep the engine tilt as low was possible, but high enough to just clear the ground..

 measure all weights in lbs

 measure All distances in inches

1/Put the sales under the hitch, a length timber long enough to JUST lift the hitch and take the weight on the scales...  with trailer level or slightly low at the front.

record the weight  call it   w1

2/ slide the boat back on the trailer about 12" to 20"

 measure the distance accruately and record it  d1.. the accuracy of this measurement is very critical to the end result

 d1

3/ now with hitch same height record the weight as before You may not be able to move the boat a full 20" as the balance on the trailer may put the hitch up in the air....if so just move back till just have enough weight to measure at the hitch....OR put a known weight on the bow deck.. say a 40L water container full right at the start , before taking 1st weight (W1)

OR simply move a lot of stowed gear equipment well forward.

Measure this weight    w2

4/ now measure the distance from the center  where the bit of wood its on the scales to the center of the axle.

d2

 Boat weight = d2(w1-w2)/d1

If put an extra weight on the bow of the boat, now subtract that weight.

Sounds strange.. like stuff like center gravity, weight of trailer etc... If one does the full calculation create the full equation, including these constants and gravity , center of mass and stuff....then compact the equation, all those factors cancel out and one is left with the above equation. Therefore if the constants like trailer weight... which we dont know cancel themselves out then we dont need that information in the 1st place lol








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Post Options Post Options   Likes (0) Likes(0)   Quote May Quote  Post ReplyReply Direct Link To This Post Posted: 10 Sep 2020 at 1:46pm
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Originally posted by Steps Steps wrote:


2/ slide the boat back on the trailer about 12" to 20"

 measure the distance accruately and record it  d1.. the accuracy of this measurement is very critical to the end result

 d1

Thanks for this Steps. Awesome read - where exactly am I measuring to and from on this?

Or are you simply saying measure how much I moved it back and keep a note?

I will give this a crack this evening :)

Jason

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Post Options Post Options   Likes (0) Likes(0)   Quote krow Quote  Post ReplyReply Direct Link To This Post Posted: 10 Sep 2020 at 7:55pm
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Way cool Steps. I tried to get my toe hitch weight one day and oops maxed out the scales. I should try it again with full tank. 
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Post Options Post Options   Likes (0) Likes(0)   Quote OneWayTraffic Quote  Post ReplyReply Direct Link To This Post Posted: 10 Sep 2020 at 8:37pm
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Drive it through a weighbridge then again without the trailer. Done. Trailer weight would be similar to a load of people and gear if you can’t do it again sans boat. My trailer for a 5m boat was 260kg minus rollers. Divide the weight by 12-18 and you have a power range in hp to go for. 12 would be ideal while 18 would be just ok for light loads slow speeds.
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Post Options Post Options   Likes (0) Likes(0)   Quote May Quote  Post ReplyReply Direct Link To This Post Posted: 10 Sep 2020 at 10:10pm
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Did a quick test using your method this evening Steps. I did however forget to put the engine down so will be off.

W1 210lb
D1 14.97”
W2 93.4lb
D2 173.62

This comes to 1350lbs or 612kg - interesting to note that the motor dry is apparently 112kg. This is with about 45l of fuel in it as well as a few small bits and pieces
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