2 Strokes Shake

[JJRJR]

Hey guys,

92 232 with twin Johnson 150 2 strokes. Original engines, about 1,800 hours I'd guess. Last weekend, had 3 large guys and about 75 gallons of fuel on board and at 4,200 RPM's, those 2 strokes were running like a top. Pushed us along and a super smooth 34 to 36 MPH @ 4,200 RPM.

BUT, at no-wake RPM, say up to 1,500, the whole boat shakes and rattles from the engines. Now, I've heard the old loopers shake, rattle, and roll at low RPM, and sing perfectly at higher RPM, but this seems a bit much.

How much, if any, shaking should I expect from those old Johnsons? Anything I should check? (plugs, etc.)

Thanks,

John

 

[seasick]

Hey guys,

92 232 with twin Johnson 150 2 strokes. Original engines, about 1,800 hours I'd guess. Last weekend, had 3 large guys and about 75 gallons of fuel on board and at 4,200 RPM's, those 2 strokes were running like a top. Pushed us along and a super smooth 34 to 36 MPH @ 4,200 RPM.

BUT, at no-wake RPM, say up to 1,500, the whole boat shakes and rattles from the engines. Now, I've heard the old loopers shake, rattle, and roll at low RPM, and sing perfectly at higher RPM, but this seems a bit much.

How much, if any, shaking should I expect from those old Johnsons? Anything I should check? (plugs, etc.)

Thanks,

John

You may have a spun hub on a prop. If the prop is a bit off balance it will shake but as the speed increases the shaking is less noticible. On the other hand if the prop shaft is bent, the vibration will increase as revs go up.
The fact that you had a heavy load would mean that the load on the props was greater and the hub bushing may have failed. All it has to do is shift a bit and it can create an imbalance
I hope that is it.

 

[grady23]

Could be fuel overload, cracked stator or one of many things. Have you changed our in-line fuel filters recently and/or checked your fuel for water??

 

[suzukidave]

sounds like one motor may be down a cylinder. my 94 johnson 200 would rev to 4800 on 5 cylinders but the low idle was rough. it was the carb.

i would start by running one engine at a time to try and isolate the issue. if it is both motors, i'd suspect bad fuel, bad ignition or batteries.

if it is one engine, run it with the cowl off and see if you can see anything obviously loose especially at the motor mounts or steering. after that you need to pull spark plug leads so one is disconnected at a time to try and isolate it to one cylinder (if removing a plug lead does not degrade performance then that cylinder is then issue). if you can get it to one cylinder then one at a time swap plugs, coil leads and coils with another cylinder to see if the problem moves with the part. if not, do a compression test. if compression is good, then it's the carb...

if it is generalized on one motor, then i guess i'd suspect fuel line/fuel filters then power pack

good luck