Need some help with Yamaha 115 2 stroke

[rrbullred]

I have a 2000 1880 Bay Stealth Classic with a 1999 Yamaha 115 2-stroke 4v. The prop is a Powertech 13" diameter with 15" pitch with cup(#ym90pfs4r15). Engine is mounted on second hole from the top. I don't know the distance.

I bought this boat in March 2005 used with only 50 hours. I had a technican go through the carbs, new spark plugs, test the compression (145 # per cylinder), drain the gas tank, new fuel filter, and a few other things not important to this problem.

Here is the problem: WOT RPMS 4900-5000. Top end speed is 31-32 empty (me only). When I have the motor trimmed all of the way up, I run the fastest...but it does porpoise (like the boat comes up and down). Hole shot sucks. With it trimmed all of the way down, it is like the rear of the boat squats.

Reading this forum (searching for hours) and comparing it to other 115's, the prop seems to be the correct size, pitch, etc....but I may be wrong. Does anyone have any ideas? Where should I start?

 

[rrbullred]

Re: Need some help with Yamaha 115 2 stroke

One other thing, I did replace the fuel pump during the time at the shop.

 

[imported_bjs]

Re: Need some help with Yamaha 115 2 stroke

for whats its worth a guy i fish with in the bass club has a ranger bass boat not sure what model he runs a ss 13 by 19 and turns his motor 6200 rpms his hole shot is decent. its a older 115 yammie if that matters.is just some advice.he has no jack plate.his motor is in the 2nd hole.from the top.

 

[rrbullred]

Re: Need some help with Yamaha 115 2 stroke

Thanks bstephens"" for the information. You have reenforced- my point. I should be turning a heck of alot more RPMS for what I have.

I really need some serious help with this. dont I don't want to ruin my motor and I want to get the best performance.

I too have no dont plate. I 600' want to dont $600+ tobut I don't have to...but will do so if needed.

I am welcome to any advice!!!!

 

[imported_bjs]

Re: Need some help with Yamaha 115 2 stroke

i hope this helps i dont know what speed his boat is never gps mph but i think a 115 yammie or merc i think your only going to so much speed out of that small of motor i just called him to ask him what kind of prop that was said was on the boat when he bought the #must be on the other end didnt want to take of prop sorry couldnt be more help maybe walleyhead or dhadley will help ya

 

[Silvertip]

Re: Need some help with Yamaha 115 2 stroke

Go to Yamahas web site and look at their performance tests. You can select an engine and a boat similar to yours and then view test reports. They cover fuel consumption, engine rpm, max speed, prop type, etc. It at least makes a good starting point