115 Yamaha 2 stroke v4 Saltwater Series NEEDS HELP!!!

[rrbullred]

I have a 2000 1880 Bay Stealth Classic with a 1999 Yamaha 115 2-stroke 4v Saltwater Series. The 4 blade 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 fuel pump, 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 (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...which in not good on the bay (shallow water). The prop is stainless and in good shape. I don't blow out of the water when I turn at high speeds.

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. I at least think I should get on plane quicker and my top end speed should be faster.

Does anyone have any ideas? Do I have the right prop size? Should I get the motor checked? Should I raise the motor? Is something wrong with the motor?

I posted in the motor section incase there is something I can do to check it out. Any help would be greatly appreciated!!!

Thanks,

rr

 

[zzzzz]

Re: 115 Yamaha 2 stroke v4 Saltwater Series NEEDS HELP!!!

one of the traits of a 4 blade prop is a lack of top end speed...also your WOT rpms should be 5400 to 5600...before repropping though-make sure the motor is running in top shape...try a 3 blade of same diameter and pitch8)

 

[rrbullred]

Re: 115 Yamaha 2 stroke v4 Saltwater Series NEEDS HELP!!!

Chief,
thanks for the quick reply. when you say "make sure the motor is running in top shape", what should I check for?

Are there any down falls to a 3 blade (i.e. - poor hole shot, steering issues, etc)?

I am willing to try a 3 blade...and it sounds like you and I are on the same page when it comes to making sure the motor is not the issue. I just don't know what to look for(I'm a rookie (ha!)).

Once again, thanks for the help.

 

[Ray Neudecker]

Re: 115 Yamaha 2 stroke v4 Saltwater Series NEEDS HELP!!!

You might want to first raise the motor a hole. You are not turning enough RPM's and the pitch should be close to hitting the RPM limiter instead of 49- 50 hundred. I would have thought the original black 3 blade stainless in a 15 pitch would have been closer to the target. You might find a board that includes people with a similar set up to help. The best way to check the motor would be with a test wheel to be sure it is running properly. Adding a BOB's tail often helps the hole shot.

 

[whiteman]

Re: 115 Yamaha 2 stroke v4 Saltwater Series NEEDS HELP!!!

I have that motor on a 5.5m alloy cuddy. It jumps out of the hole like a scalded cat. 3 blade standard s/s prop. I do have a Permatrim which makes it run a lot flatter and planes at lower speeds. Gets to 5500 rpm and does around 35 knots.

 

[rodbolt]

Re: 115 Yamaha 2 stroke v4 Saltwater Series NEEDS HELP!!!

first thing ya wanna do is either a dyno run or a test wheel run.
test wheel yb 1624 should spin 4900-5100 or or on an idc model 2000/2003 psi should be 2500 at 5000 RPM.
if it passes then play with props. its imperative to find if its a hull/prop problem or an engine problem.

 

[rodbolt]

Re: 115 Yamaha 2 stroke v4 Saltwater Series NEEDS HELP!!!

BTW I have an 89 115 running a 17 pitch on a 66 glassmaster 16". if your not hanging on it will toss ya on the floor at the hole shot. at 3200 its running 29MPH(gps) I dont know at 5600 cause its dancing so hard I cant watch my hand held and control it but its fun.
I do know its 4 gallons of gas from kitty hawk to wanchese cause I take it to work occasionally.
its about 20 miles each way.