Boat wont plane

[paulc81]

Hi all, looking for a little knowledge as im at the edge of my nerves with this. Ive got a 1986 Searay 21' cuddy w/a 5.7 merc. I had 4 ppl (700lbs) in the boat and she was hesitant to plane off, but did. I then topped off my gas tank w/ about 20 gallons. On the way out of the marina when i opened the throttle, rpm's wouldnt go over 3000 and she wouldnt plane out, causing a engine rod to bend. A week later I swapped the rod out and retested the boat, same results, would not plane w, just me on the boat. Boat is freshly bottom painted this season, however i did see some amount of growth on prop, but most came off naturally on way out of marina. What to do next???? PS tilt/trim all working properlyand ive owned the boat about 5 yrs without this problem

 

[45Auto]

Re: Boat wont plane

Sounds like you've got it backwards to me. Whatever engine problem you were having that prevented it from planing is what bent the rod. "Not planing" was a symptom of the problem, not the cause.

Sounds like you need a complete engine check out/tune up - compression test, timing, plugs, cap, rotor, etc. How old are the manifolds, you could easily have water in the engine if they're original.

 

[Andy'sDelight]

Re: Boat wont plane

I agree with 45. Noty getting over 3000 RPM's is a symptom of the engine, and the reason you're not planing. Start with a compression test. Bending rods is bad news.

 

[Bifflefan]

Re: Boat wont plane

How did you change an engine rod (piston rod I assume) with the engine in the boat and the boat in the water?
I say in the water because you said you have fresh bottom paint and some growth on the drive, but did not say anything about the bottom.

Sounds like you have an engine issue.

 

[Chris1956]

Re: Boat wont plane

That sounds like a significant engine problem. That motor should have plenty of power as you know. I would take a compression test and repost issue in the I/O Forum.

Did you change the prop?

 

[dmoriarty51]

Re: Boat wont plane

How did you change an engine rod (piston rod I assume) with the engine in the boat and the boat in the water?
I say in the water because you said you have fresh bottom paint and some growth on the drive, but did not say anything about the bottom.

Sounds like you have an engine issue.

perhaps a pushrod rather than a connecting rod

 

[paulc81]

Re: Boat wont plane

That sounds like a significant engine problem. That motor should have plenty of power as you know. I would take a compression test and repost issue in the I/O Forum.

Did you change the prop?

Prop hasnt been changed since before the occurance of the problem, I will post results of a comprssion test asap, yes it was a pushrod that was changed.manifolds/risers in good shape, acetone tested/painted seasonally as needed

 

[paulc81]

Re: Boat wont plane

thread moved to IO forum Thank you