Thanks guys. I’ll take it down to my local Yamaha dealer and see what they think about the motor position. I do have a hydrofoil on it to help get it up on the plane.
Yeah I can troll at 6 knots and the economy gets better, still about 8.5 - 9 lph.
Was the 200hp too heavy for the boat?

I saw an earlier post of a guy with a 565 Billfisher with a 130 Yamaha on it and it looked like some pretty impressive fuel figures. Same block as my 115 but dohc I beleive?

Bill fisher 5.5 wrote: Thanks guys. I’ll take it down to my local Yamaha dealer and see what they think about the motor position. I do have a hydrofoil on it to help get it up on the plane. Yeah I can troll at 6 knots and the economy gets better, still about 8.5 - 9 lph. Was the 200hp too heavy for the boat? I saw an earlier post of a guy with a 565 Billfisher with a 130 Yamaha on it and it looked like some pretty impressive fuel figures. Same block as my 115 but dohc I beleive?

Rough guide to tabs or foils

Same thing before going trim tabs..
Rule of bthumb, be it dialing a hot rod engine in or powering propping.. only change one paremeter at a time..
 The propping very important the order is corect..
 1/ Engine height , thu this can change with more extreme prop changes.
2/ get the prop slip factor right at WoT and around 4000 rpm cruise speeds for general use boats.. custom use say lower cruise in more choppy seas the norm, or long periods trolling..or on the back of a barge usualy slightly different.
3/ Then sort pitch

 2 and 3 with experience and good data bases, good accurate rpm/ speed data and if in ball park can be done together.

 Props hard to source from local dealers on loan...
 best bet is find out from sea trail data if yours is in ball park.
 From there will be able to calculate very close to ideal. Then watch Trademe and keep a look out for props reasonasbly priced..
Reasonable . a good SS will be around $150/ to 200
 And alloy $50 to 150.
 Alloy or SS.. alloy flex, they flex on a approx 5.5m hull around 1200kg  when gets up around the 35 / 38 mph , but not enough to significantly effect performance or economy. At trolling speeds nothing upto around 6.5m 1800/2000kg.. above that I have no data.
 So a elcheapo alloy off trade me is the best way to go then look at Actual needs further down the line.
 

After running my wee boat for 6 months it seems to now be pretty consistent.

PS. Check before you buy, some 4stroke outboards need to run on 95octane OUCH $$$$ 

 Read you manuals 1st..
USA measures octane different than most of the rest of the world... so careful if it is a American manual
 There are 3 basic measurements for octane.. one high one is low and the other and ave of the 2.
American 95 is very close to our 91.
 Also you will find running a engine that requires higher octane $ per mile , will work out about the same than the lower octane fuel. Run a high octane engine on low octane  thinking will be cheaper, you will end up with long term issues and the $ per mile will be higher...

I dont hit in miss method but rather
 1/ Sort engine height.. may have to be changed for different conditions/ applications later
2/ Sort out the correct slip numbers for WoT , normal load for that size hull Sorting slip numbers is critical to do before moving on. If change engine heigh this has to be redone/ tweaked
3/Then match the pitch into the mid way of the WoT specs for that engine.
Reasons for midway is under normal load then have alight load , you go towards the max spec and visa versa for heavy load/ towing  within reason.

4/ From there one selects the amount of cupping  and/ or rake to fine tune for different uses and applications. And also engine height can be correct in one set conditions and not another, regardless of prop make type etc.
 And then throw in different gear box ratios..

Also the amount of power to hull weight (we are only talking planing hulls that actually plain..)  .. If min power , max, over powered... all effect how a given hull will react in different seas and applications.

Then we throw in 3 and 4 blade and the whole thing totally changes again... even engine height if on the cuspe between holes.

So to pick out a particular prop brand/ type/ model. then ask thoughts on it is much of a moot point given so many variables between even identical rigs... weight gear /crew/ east coast/ west coast

Do you have the data numbers , in particular the slip numbers for each of the comparisons above.?.. That would be very interesting and would show up a lot of info as to what is happening.

 Yes used Enertia, 4 blade 3 blade high rake, huge blade areas, big cupping slight cupping... alsorts brands models.. And now have quite a collection  hanging from my shed rafters.

Thanks for the correction Roz.
Later on in the days , sorting bench a sink/tap off couple IBC tanks plumbing was wondering if got it the right way round...
Usually only check internet/ emails etc once a day over morning coffee.

Sweet, what pitch Enertia did you go for? Is it the original Enertia or the Eco Enertia [which is bigger diameter] for multi engine offshore hulls

His last log in visit wa 13 march.. maybe he , like others have mentioned in replying to posts is/ has been having trouble logging back in..