70 hp johnson wont exceed 4000 rpm

[beckley8]

I have a 70 HP Johnson with a vro pump on it. Engine excelates great but shakes like hitting a rev limiter at 4000 rpm compression about 130 all cyl good spark tried spraying fuel down carbs when prob arives engine bogs down on each cyl. Did a drop test at wot and each cyl seems to drop the same rpm. Any ideas is this a stator issue

 

[Daviet]

Re: 70 hp johnson wont exceed 4000 rpm

So it acts like something is out of balance rather than a miss?

 

[beckley8]

Re: 70 hp johnson wont exceed 4000 rpm

I have a 70 HP Johnson with a vro pump on it. Engine excelates great but shakes like hitting a rev limiter at 4000 rpm compression about 130 all cyl good spark tried spraying fuel down carbs when prob arives engine bogs down on each cyl. Did a drop test at wot and each cyl seems to drop the same rpm. Any ideas is this a stator issue

Its not a hard miss like a lean pop or a single cyl miss firing it will run at 3700 rpm smoothly no problem did notice a little engine shake at idle. Its almost like the timing doesn't advance enough. There is a new timer base on this engine. Engine will shake at wot. When it shakes it stays at a constant rpm every fustrating

 

[ferdly1]

Re: 70 hp johnson wont exceed 4000 rpm

Almost sounds like a bent prop shaft or prop. with motor off raise motor spin prop and see if you see any wobble. Only takes a few seconds.

 

[beckley8]

Re: 70 hp johnson wont exceed 4000 rpm

Prop has 2 little dents not much at all prop shaft to the naked eye looks good without putting a dial indicator on it. Everything seems tight with a little prop shaft endplay. The shaking is like slow mode just not as violent I suppose. I manually put it in slow mode to make sure that wasn't it. The idle can be irregular at times almost like the timing got advanced somehow.

 

[ferdly1]

Re: 70 hp johnson wont exceed 4000 rpm

ok it was just a thought. mine shakes and my shaft is definitely bent. it has been that way for a while. so many stumps in my lake,waste of time fixing it.

 

[beckley8]

Re: 70 hp johnson wont exceed 4000 rpm

Thanks for the idea. If you have any other ideas please shoot them my way