225 HPDI Vmax vibration

I just bought a 225 HPDI that has 40 hrs on the top end. It runs realy good, but it has a small vibration between 2300 and 2800 RPMs. Or around that area. It also does it if you rev it in neutral. It doesn't vibrate after it gets through that range. Its not a bad vibration, I'm wondering if it is normal?? And if it is not, what could it be?


Thanks for the help.

I’m fairly positive that hpdi idles only on 4 cylinders and you can’t rev it up in neutral very much. So your vibration in neutral is normal but it should be smooth in gear at higher rpm.

The motor does it under load at about 1/4 throttle then it smoothes out. It idles smooth also. Do the 3.3 litres normally run smooth at all throttle positions? This motor has had the powerhead changed, is it possible something is out of alingment? It runs too good for it to be something like a bearing or piston making it vibrate. All the plugs look normal after having the injectors cleaned.

Where should I start looking? Any suggestions?


Thanks

it is probably prop related.

Unbalanced prop or bent prop shaft will definitely cause vibration. But also check all engine mounting bolts, flywheel, compressor belt and pulleys.

I feel it some when I rev it in neutral also. Hopefully that vibration is because it doesn't idle on all cylinders. The prop shaft isn't bent. I'll try a different prop on it next time I take it out. Hopefully thats the problem.


Thanks

I haven't noticed it on mine, but I'll check it next time I go.

All the big block yammies do it, I'm amazed that more people don't notice it...

The new 250HPDI I drove I thought was really bad. But only at light throttle and around the 2500rpm mark. Like you said 2300-2800rpm. Seems to be most noticable with a low pitched prop on a light boat doing a light task eg a ski boat. With a tall you'd only run 2500rpm on the way to getting on the plane and it would be full throttle so you'd never notice.

I've driven others and they do it also. You have nothing to worry about this is how those motors are.

I tried a different prop today, and it does it at the same RPMs. I was hoping that it was normal. I won't worry about it until it gets worse.

Thanks

Any chance the motor is fitted with solid engine mounts? That will make it really, really noticable (not terrible).

The owner of one, fitted to a ski boat hadn't noticed it I guess he'd never done that speed. When we looked at it on the ramp, my wife told me we had to have one (250HPDI). Once we test drove it, my wife told me we are never having one for that very vibration 2300-2800. She is pretty switched on with that kind of stuff.

I suspect Yamaha didn't concentrate on light hulls with short props on the big block engines. Not many people turn those kind of revs with these motors except at full throttle on the way to getting on the plane.

thanks for the help. I don't hold it there, I just felt it and didn't know if I should be concerned with it or not. Its an aluminum boat, and the hull is very ridgid, so it is possible that is the reason I am feeling it.

I am unsure about the mounts, but if it didn't come from Yamaha with solid mounts, I'm sure the previous owner didn't install them or have them installed.


Thanks

I would have a look at one of the reed valves going bad.That will cause a bad vibration at low rpm's then smooth out at upper rpm's.