I have a 99 formula 330ss with twin 7.4 mpi and this spring I replaced the flywheel ring gear due to some chipped teeth. I finally put it all back together and put it in the water. Now I am experiencing a new problem. When I power up around 1800-3k rpms it seems to not have the power it had before and it has a bad vibration that resonates thru-out the boat. Once i get up on plane and push it to the max it goes away and runs great but as soon as I back it down it comes back around those rpms. One concern i have is that after i had everything put back together i found the little spring washer that belongs on the rear ear mounts laying in the bilge. So its not installed on the one mount. The outdrive went on fine so i didnt think the alignment was off. Could the missing spacer be causing vibration or is it something more? Coupler? Any help would be greatly appreciated. thanks in advance

Sounds like a harmonic vibration, possibly due to new flywheel not being matched with crank balancer but I'm no expert. Also check your timing for the hesitation. I don't think the two issues are related. Someone smarter than me should chime in soon. good luck.

The flywheel is the same one thst was on there before just with a new ring gear. Is there a particuker mark that needs to be lined up?

WAG. Not having the fibre washer and the metal to metal (alum) contact is not only transmitting more vibration but is also causing your knock sensor to trigger and causing this loss of power.

I've had exhausts do this on car and sled EFI's. Those where a bugger to figure out back then.

Go here: http://www.mercruiserparts.com/selec..._nbr=BRAVO+ONE
Click on which serial # Bravo you have, then click " transom plate " to see order. Also see loock up of parts it will give you dimension of each washer and a # and then look back at pic so you can see which goes exactly where.

Im not sure if im describing it correctly buy when i power up its hard to determine if its losing power, prop slip or just the intense vibration is just makng it seem as though its not gaining speed but it does go away and power forward. Would the missing washers make it shake harder when trying to come up on plane due to the added stress/ work than once it gets up on top? I know it sounds confusing but its an odd problem? It ran great last season and now the onky thing different is the missing washer and spring on one side but its so small i couldnt see how that would cause a vibration.

You ever drive a car with solid motor mounts ?

Yes good point. Wouldnt it still vibrate in neutral? It does not. This is a little upsetting that i will need to pull it out again to put a 6 dollar washer in. I wasnt able to locate it when reinstallng so thought it was never there but hard lesson learned.

Do you think it would be possible to lift the motor that 1/2 inch to slip the washers in with the drive still attached??. Im trying to avoid the marina pulling it out if i can.

Gotchya. Maybe. I dunno. Haven't been faced with that, as in having to pay someone else for that. I did have a boat come to me to finish some stuff where the bolts, spacers, washers where in wrong. I fixed that and other things before boat whent in water so I can't say what would have happened if I didn't.

In my job, you have to fix known problems first, and then move on if that doesn't fix why the vehicle's there.

Again, I WAG in my part on what's happening to you, but again, know problems have to be dealt with first.

You only have two things different as far as we know, missing washers/spring and a new ring gear.

I picked one, the one I can answer from a keyboard that's not right. I can't answer for the ring gear. Or anything else. Sorry.