vibration under load

[skiboarder]

I HAVE A VIBRATION ISSUE. WHEN I HAVE THE BOAT LOADED WITH PEOPLE AND GIVE IT A GOOD AMOUNT OF THROTTLE IT HAS A VIBRATION,DONT THINK IT IS NORMAL. EVEN WHEN  YOU PULLED UP A SKIER OR BOARD.HAD A ALIGNMENT DONE HELPED A LITTLE COULD THE PROP BE OUT OF BALANCE? ANY IDEAS

[eagle1wi]

When mine vibrated it was the prop.

Is it certain RPMs that it seems to be worse than others?

For example once you break 2500 RPMs it seems to be reduced.

[lesman01]

Most likely the prop. Go with an Acme prop. It's machined to be in perfect balance. Seardch for Acme on the board and you'll get lots of info.

and

YOU DON'T HAVE TO SHOUT. All caps is considered shouting in internet board-speak... (-; There are times to shout, but don;t think you meant to shout this one.... like when Bitzo has a tire on his mobile home go flat...now there's a time to SHOUT DAD GUMMIT!

[skiboarder]

the prop is not even that bad my friend is a marine tech and when he did the alignment he filed down a couple of nicks on the prop.and yah it seems to get better after you pull a skier up out of the water its just when you punch it

[eagle1wi]

the prop can be out of whack and still look fine

it could also be a cylinder missing if it is more apparant under load

[HCollado]

 
Have you switched the quality of gasoline. In other words, be sure to run premium. I ran 10 gallons of regular once and the boat felt like it was coming apart under load. I even whent as far as buying a new prop thinking it was the prop.

Have you hit anything?

[skiboarder]

I really don't think it is anything with the engine she runs great but I will look into that. Ive been running premium eversince i got it and i haven't hit anything that i know of. If the prop is out of whack can that be rebalanced. thanks guys

[eagle1wi]

Yes it usually can be fixed.

This guy is pretty close to us:

http://www.propsahoy.com/index.html

I met him at the boat show but I haven't given him any business yet.  My XMP OJ is still smooth as silk.

There are shops that you mail it out to as well, but since he is local his turnaround is probably better.

[lesman01]

I had my original OJ reworked when I bought the boat, but either was too dumb to notice the slight vibration or thought it was "normal" for vdrives to have a little vibration getting up to speed. when I put my CNC Acme prop on all vibration went away. 

[skiboarder]

thanks

[sailtl]

Make sure the bolts & nuts that attach the drive shaft to the transmission flang are tight. Mine kept coming loose. Blue LocTight solved my problem with the nuts coming loose. It sets up a vibration like the prop is bad. You may also hear a slight clunk when putting into gear.

[cyclone]

What Terry (SailTL) said!! I had a funny noise and vibration that developed, turns out that two of the four 3/8 x 2" bolts were MISSING and the other two were within a couple of threads of falling out.:0

I quickly tightened them, replaced the missing ones, all good. I will still have nightmares about the shaft letting go at 5K rpm, sliding back, hitting the rudder and destroying it, ripping a hole in the hull, complete loss of watertight integrity, all hands lost......

CHECK YOURS IMMEDIATELY you need 2 x 9/16 wrenches. 14 mm will sort of work but the bolts and nuts are SAE.

[tryme]

same thing happened to me.  had an old oj prop never hit anthing that i thougtht.  then one day vibration at higher RPM.   really small ding.  replaced it with a new ACME prop and went away.   and gave the boat a huge differerence in hole shot!!