Sorry for not being the most qualified mechanic but Im need of some help. Im probabaly rambling but please bear with me.

Boat: 14x48 Lowe w pods
Engine: 25 kohler
Load: 2 guys, tons of shit.

In deep water, under load my engine knocks, or bangs or something. At first I thought it was a loose prop but I doubt it. I asked my hunting patner to come to the stern of the boat and run the motor WOT so I could hang out back and identify the sound. He opens the boat up and it taked off like a bat outta hell and no noise. I realize I have a weight distribution problem, no biggie. So I climb into the front seat and he gives it WOT and it knocks for him. Its not ideal to have 2 guys on the back seat at all times so I need to identify the sound.

At idle, and on plane there is no knock, we ran WOT for a half hour with no problem, oil is fresh motor sounds great. Under load and trying to plane, or plowing for that matter I still get the noise every few seconds. Once on plane or in the shallows it stops.

I have a feeling Im getting to much fuel and its backfiring. But the sound doesnt come out of the exhaust. It actually sounds like a bad bearing but I doubt that as well. If I had to describe it it feels like a faulty transmitting in ia car, a little slip and a bang into gear. Does my motor have a clutch? Any help would be gratly appreciated, as its dead winter here and breaking down isnt an option.

Additionally, I just put a new battery in the boat and it struggles to make the 1st crank when starting. IDK where to go with that one either. Thanks, john

valve push rods bent

Could be a faulty lifter too, but hard to say with that description and not really having any idea where the noise is coming from. Could be detonation...just don't know without knowing what exactly it sounds like and where the noise is coming from. You can def pop the valve covers off and look at the rods.

It could even be the frame shaking on the mounting bracket if you aren't very mechanically inclined it sounds a lot like a knock at idle.

My 13mblt would rattle on the frame until you loaded it in the mud or got out of the RPM range it didn't like.

Mine does a little also when its trimmed all the way down in the mud bogged down... But not much at all..

Does my motor have a clutch?

What brand of motor do you have??? A little more info would be helpful. If is has neutral it has a clutch.

I can get a knock in my motor if I trim all the way down in the mud and run 89 octaine. I always run 93 in mine but we were out at cabin and thats all we had in the cans. Not making a 2 hour round trip for 6 gal. of gas.

Gonna tighten prop to rule that out. Run high test and add ring free to my next tank. I been using 87 and I guess thay may be part of the problem

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Easy on the prop killer she's supposed to spin by hand 1/4 turn

prop may be to deep in the water, try adjusting your trim

adjust your valves

X2

Did you ever fix the problem? What was wrong? I have the same engine doing the exact same thing.

1st thing I would try is running a higher octane fuel.
If that didn't help, I would pull the valve covers and check the travel. If you have a bad lifter it will feel spongy and not fully open the valve. Then check your pushrods.

What was the problem?

Any feedback on what the problem was?


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Just read through this sorry I didn't see this sooner right from the initial post it sounded like the notorious bad Kohler head gasket problem where it bogs down and sounds like hell under load. Glad you got it fixed my Prodrive started doing this the last day of duck season I knew exactly the problem when it started it. Needs to warm up 40 degrees outside so I can replace it lol


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