Intermittent inability to plane the boat

[Sheff 69]

I am having a strange problem with the 2002 90TLRA on my Key West 17' boat.

Couple of days ago, I experienced a problem where after being out for a couple of hours, I couldn't get the boat onto a plane. When I opened the throttle, the rpms would rise, and the bow would lift, but that was it. It would run at about 4500 rpm with the bow sitting up high, but I couldn't get onto a plane.

I initially thought I had spun the prop (Michigan wheel 13.25 X 15 SS prop), so I bought a new Yamaha 13.5 X 15 aluminum prop.

Today I took the boat out, started great and lifted onto a plane easily, but after a couple of hours, the same thing happened. Couldn't get onto a plane, engine rpms maxxed out at about 4500 running bow high.
After idling back into the dock, I pulled the plugs and found they were wet, not black and sooty, just wet.

Does anyone have any ideas as to what may be happening?

Is it possible to spin something inside the lower unit that slips when warm?

John

[99yam40]

I do not understand putting a bigger prop on to see if that helped.
if the motor cannot turn a prop, going bigger would not help.

need to have the motor checked out,
fuel pressure/pump would be the 1st thing I would be looking at.
but then compression, spark and timing would be good too

[pstephens46]

Did the boat require more than 4500 rpm to get on plane before? If the prop or gears were “slipping” I would think the rpm would increase rapidly to the point of having to reduce throttle. Nothing bad about now having a spare prop.

[TownsendsFJR1300]

Stupid question, but did you check to make sure your not taking on water in the hull after awhile?

[DennisG01]

Agree with above - sure doesn't sound like a spun hub... or a "spun" anything. The engine RPM's would skyrocket if that was the case.

Are you trimming down all the way? Can you verify the engine is still going full down when this happens?

As mentioned... how does that 4,500 "no plane" compare to the times when it does plane? 4,500 sounds like it's plenty for a lightweight boat, though.

[Sheff 69]

I do not understand putting a bigger prop on to see if that helped.
if the motor cannot turn a prop, going bigger would not help.

need to have the motor checked out,
fuel pressure/pump would be the 1st thing I would be looking at.
but then compression, spark and timing would be good too

I was only trying to test for a spun prop.
I needed a spare prop anyway and Yamaha don't make a 13.25 dia prop.
The yamaha boat dealer said that was the prop they would have recommended for my boat.
The next time I take it out, I will make allowance for pulling over out of the high traffic lanes and test for fuel in the carb bowls.
I have to be careful, I'm on the intracoastal and the water depths at the side can get shallow real quick.

I will also now test for compression, last year mechanic checked and said I had 119-121 in all cylinders. I'll check.
Starts good and spark seems good coming off the water, but I haven't checked timing.
Note, going out is great. It's the coming back that sucks.

Thanks
.

[Sheff 69]

Did the boat require more than 4500 rpm to get on plane before? If the prop or gears were “slipping” I would think the rpm would increase rapidly to the point of having to reduce throttle. Nothing bad about now having a spare prop.

I normally run one up, and it gets on plane at about 2600 rpm, this time I was three up and going out was about 3200 rpm. Coming back I couldn't get on plane.
I agree about the slippage and the engine rpm, but it didn't get any higher than about 4500 rpm.
I just can't figure out how the engine can get to 4500 rpm and not get on plane.
I did need the prop though!

[Sheff 69]

Stupid question, but did you check to make sure your not taking on water in the hull after awhile?

Thanks I hadn't thought of that, but I always pull the bilge plug when I'm on the ramp when pulling out. This time there was no water in the bilge.
In fact when I pull the deck plate cover when out, I am still dry.

[Sheff 69]

Agree with above - sure doesn't sound like a spun hub... or a "spun" anything. The engine RPM's would skyrocket if that was the case.

Are you trimming down all the way? Can you verify the engine is still going full down when this happens?

As mentioned... how does that 4,500 "no plane" compare to the times when it does plane? 4,500 sounds like it's plenty for a lightweight boat, though.

I agre now, but when you are reading up on the internet, odd things sound plausible.
When I go out from the marina, I can plane easily, about 3200 rpm
Yes I am trimmed all the way down. Visually identified as hitting the trim pin

[DennisG01]

I agre now, but when you are reading up on the internet, odd things sound plausible.

Yeah, don't trust everything you read on the internet... wait a minute... you're reading what I AM writing on the internet...

There's definitely nothing in the lower unit that can cause this. If that was shot, you would ABSOLUTELY know it... and it wouldn't "fix itself" every so often.

Could you maybe have had something wrapped on the lower unit or dragging something?

If you're turning 4,500RPMS, that means the prop is turning fast enough... which "I think" negates anything being wrong with the engine, right? If the engine was weak, it wouldn't turn 4,500 in the water under load trying to get up onto plane unless the prop was bad. In other words, from the engine to the prop is a solid connection (gears). The only non-solid thing is the prop hub - which has already been ruled out for a number of reasons.

Reading back through your response... When you say "hit the trim pin"... That makes it sound like the engine was tilted up, then as you pressed the "down" button, the tilt ram lowered the engine until you came into contact with the trim rams... and you STOPPED. You need to keep going until the trim rams are fully compressed (you'll hear the trim motor make a different sound - sort of like when you turn your car's steering wheel all the way to one direction). Maybe it was just the way you worded things, but just want to be sure.

[Sheff 69]

Yeah, don't trust everything you read on the internet... wait a minute... you're reading what I AM writing on the internet...

There's definitely nothing in the lower unit that can cause this. If that was shot, you would ABSOLUTELY know it... and it wouldn't "fix itself" every so often.

Could you maybe have had something wrapped on the lower unit or dragging something?

If you're turning 4,500RPMS, that means the prop is turning fast enough... which "I think" negates anything being wrong with the engine, right? If the engine was weak, it wouldn't turn 4,500 in the water under load trying to get up onto plane unless the prop was bad. In other words, from the engine to the prop is a solid connection (gears). The only non-solid thing is the prop hub - which has already been ruled out for a number of reasons.

Reading back through your response... When you say "hit the trim pin"... That makes it sound like the engine was tilted up, then as you pressed the "down" button, the tilt ram lowered the engine until you came into contact with the trim rams... and you STOPPED. You need to keep going until the trim rams are fully compressed (you'll hear the trim motor make a different sound - sort of like when you turn your car's steering wheel all the way to one direction). Maybe it was just the way you worded things, but just want to be sure.

No that was my bad words.
The trim pin is the pin right down at the bottom by the transom, so when the motor is trimmed down, it goes down until it stops just short of the transom.

What you are saying is what I felt.
This is weird, if the motor can make 4500 rpm there is nothing slipping, yet if it normally planes at 3200 rpm, why doesn't it?
I have nothing off the back, since I just changed the prop, there is no line etc, or I have taken on water, so what is happening?

At a loss.

[DennisG01]

Does the engine "sound" like it's turning 4500? Does the engine sound normal?

When this happened, did you have issues all the way back to the marina, or did it eventually get back to normal?

Where you possibly in a shallow, weedy area - where the weeds could be the issue? They could wrap around the engine and cause excessive drag.

[Zara Spook]

Why are your RPM maxing out at 4500 and not somewhere around 5500? If it were me I would check into things that addressed that question before doing anything else.

[DennisG01]

Why are your RPM maxing out at 4500 and not somewhere around 5500? If it were me I would check into things that addressed that question before doing anything else.

It's because when this "issue" happens, he can't get the boat up on plane to where the prop would eventually spin faster.

[zenoahphobic]

Two only possibilities.
one your engine is shot,or
two your boat has changed in someway causing extra drag. Look for hull damage.