Plaining Problems

[Okieracing]

I have a 1993 17' Cajon bass boat. I has a 1993 115hp (C115TLRR) Yamaha 2 stroke motor. This is a newly bought boat for me. I took it out fishing yesterday and I had a problem with it plaining. When my live well had water in it I could not plain what so ever (well is in the back of the boat). When I would drain it as I was moving it would plain right out. The boat has a forward well also. The guy who had the boat before me caped off the fill for it so it is not used. I thought about mounting a plainer to the shaft of the outboard or the the back of the boat itself. I also thought changing prop too. I am not sure what prop I have on the motor. I could not find any numbers on the prop to tell me what I had but I figure it is a stock prop for that motor. It is a stainless 3 blade prop. Does anyone have a suggestion on which way I should go?

[TownsendsFJR1300]

What's the max RPM the motor is turning now?

[Okieracing]

I am not sure what the max RPM is. I didn't notice it when I was out. But if I would have to guess. I would say around 3K or 4K RPM.

[99yam40]

Compression, spark, and timing all should be checked.

more fuel is needed to provide power even to cylinders that are all good
Test what you can and then look into fuel to air ratio problems( cleaning carbs,fuel pump,etc.)

I just reread your post, and you have never been able to get it up on plan well

what is the boat rated for in HP?
how heavy is the boat?
it may be just that you have too little HP or the wrong prop.
there is no standard prop, has to be matched to boat and motor

[boscoe99]

You need to do a wide open throttle RPM check. With the boat loaded and the motor trimmed up just to the point of best boat speed. No further. The WOT RPM should be at or near 5500 RPM.

What is the boat speed when at WOT?

Inspect the propeller for any marking that might give a clue as to what it is and who it is made by.

[Jason2tpa]

I wasn't familiar with your boat so I had to look up the dry weight specs...depending on the 17' model the dry weight range from 750lbs to 900lbs. If this is correct then I can say with certainty that the livewell full or empty isn't the cause of the boat's inability to get on plane....unless you've got a 50 gallon well in that 17' boat. Based on the beam specs I reckon your livewell holds 10-20 gallons, right? So we're talking about a full livewell (excluding weight of bait) weighing between 80lbs and 160lbs. Which isn't nearly enough weight to prevent your boat from planing.

There will definitely be a noticeable difference when jumping on plane with a empty or full well....but even with a full livewell the 115 hp on that hull should have no issues jumping on plane, especially with the 115 hp being a 2 stroke. So it sounds like you've got 1 of 2, or 2 of 2 issues....under performing motor and over-propped. Townsend asked you the most important variable relating to this issue that you'll want to know...what are your max rpms @ WOT. The spec rpm range for your engine is 4500-5500. I'm guessing you're not even reaching the bottom end of spec since you can't get on plane with a full livewell. And if you are over-propped this will only exacerbate the effect of the poorly performing engine.

I'd take the prop off and give it a good look around. Usually but not always, prop manufacturers will press at least a number or letter on the prop. If you can't find anything then hopefully you live in close proximity to a prop shop. Bring them your prop and they can measure the pitch.

By the way, I have a '98 115. If you can hear the words coming out of the person's mouth sitting next to you while running the engine at WOT then you can be certain the engine is not reaching the top end of spec rpms. Cause that s.o.b. is-a screaming at WOT.

[DennisG01]

Agree with the first line of attack being finding out your MAX WOT RPM. Do this with a minimal load to eliminate any variables. Hammer down and slowly trim up until the speed no longer increases or the prop starts to ventilate. It's OK if you go a couple hundred RPM's over your engine's MAX for this test - this is just a brief run to get some baseline numbers. Once you have those numbers, post back and it will be easier to help you. Ideally, I'd like to prop a boat for MAX RPM with a normal load in it, but to make things easier via a forum (eliminate variables), I would suggest doing this test with a minimal load. Otherwise, everyone's definition of "load" can be different.

One thing that is sometimes overlooked by newer boaters is growth on the bottom of the boat/motor and or damaged prop. Even just a 1/4" slime layer can have a HUGE impact on performance.