plumb crazy

I ran my boat yesterday ran it up to 90 or so when I let off the gas (quickly) the drive made a nasty clunk . I think it's the water pushing the prop backwards witch can't be good. This can't be the only boat that does this so does any body no what to do?

plumb crazy

The drive is a bravo 1 on a Eliminator Daytona 650hp. You can feel and hear the noise it's like the water slams the prop backwards it makes one big clunk then it's fine . If I bring the speed down slower witch is what I try to do it just fine . Last year it did the same thing I thought it was slop in the steering but I just but on full hydraulic. With a nose cone there is so much water pushing on the prop thats what it's got to be .

Brad Zastrow

I am guessing major problems in the drive. At this point have it looked at or torn down before it is totaly destroyed.

Falcon

Forgive me for jumping in.
Bravo's "overrun" when you back off hard on the throttle. The prop will try to spin at close to boat speed while the engine rpm is lower, but I don't think the clutch would cause a noticeable noise. Sudden decel of the engine combined with water reentry at high speed "could" pull hard enough on the drive trim to cause the drive to pop off the trim relief pistons. Then when you throttle back up, it can slam back to the original position causing what could be a very noticeable noise. But this still does not sound like what you describe because you say it is when you decel, not throttle back up.

Falcon

Bravo's have relief pistons in the trim cylinders too. It has a special 2 part piston that can let the drive trim out with enough impact, then it can return to the same position after the impact (memory piston). Doubt it is the issue described here.

Mr Gadgets

Is everything on the transom tight? You can get a side to side motion when accel/decel if there is something loose??
Is the propshaft tight? No end play, rotates with some preload on the bearings that it rides on?
Does it do it at medium speeds?? Like 50-70mph range or just at 90mph??
Anyone else in the boat that can try and locate the noise as it happens?? Have the wife ride on the swim platform and see if she can feel or see it?? (sorry couldnt resist)..

Just thinking out loud here..

plumb crazy

The drive is new , It's put on right , prop is good an tight, no noise at 50 to 70 mph only when let off gas 100% at 85 an over . Back the gas off slow an were fine. Wife is always on swim platform.

US1 Fountain

iTrader: (1)

Did you remember the plastic spacer at the trim ram?

Mr Gadgets

She likes to hang on at 90mph?? That makes her a keeper!!

US1 has a good thought there... You could buy a camera and mount it on the transom to watch what might be happening?? They call them lipstick cams.. on ebay. Plug into your video cam that sits in the boat and records..

This is a good one... keep looking, you wil find it.

Todd Hartigh

The spacer is a good one! I let off instantly ONCE and twisted/sheered the yoke (input shaft)

Mr. Gadgets,
Thanks again Dick for fixing my drive!! Greatly appreciated!!!