Strange noise from GT40

[rleinen79]

I recently purchased a 97 SNOB from a local marina. It was a trade in on a new one. When I test drove it in October, I knew I wanted it. Only problem was, 20 minutes or so into the test, it started making a loud humming noise that could be heard over the engine at about 2700 rpms. It got louder and quiter as the rpms raised and lowered. We shut it off, waited 2 or 3 minutes and restarted it, and it never did it again. The owner of the marina was with and he said that it was the belts humming and they would replace them over the winter. Anyway, long story longer, they changed the belts, oil, and impeller, but the boat did the exact same thing the first time I took it out last weekend. It will run for hours at 1900 or so RPMs, but once you kick it up for any extended amount of time, that noise starts again. It's got the fuel injected GT 40. Any ideas?

Thanks

[M3Fan]

RE: Strange noise from GT40

I'd open the hatch and find out where the noise is coming from. Could be something else, like the trans or drivetrain. Does it do it when it is out of gear?

[SGY]

RE: Strange noise from GT40

M3Fan is right. I'd start checking it out. I'd also call the dealer and remind them that this was a problem when you tested it and its not fixed as they warranted. Good luck.

[rleinen79]

Yup.....tried to do that, but as soon as you back off, it stops. And it doesn't do it in neutral when you rev it up. I've already got a call into the dealer, but I kind of get the impression that they're not real worried about it. They are a Nautique dealer, but maybe they don't care about it as much because it was an 8 year old brokered boat, and not a $50,000 Air Nautique. I'll call them again on Monday though.

[Rick]

May be a bent prop, or prop shaft or just out of alignmrent.

[M3Fan]

Ok, next time it happens, pop that engine hatch at speed and see where the noise is generally coming from. That will help a lot. You've got alignment, strut bushings, trans, prop, etc, could all be culprits. Could be the decorative housing on the engine vibrating for all we know.

[83sn2001]

Had a Marlin skier do the same thing years ago and it ended up being the alignment was off.Didn't realize it until the shaft broke in the coupler.It is worth checking out.

[SGY]

Is the noise consistent? If so, you might have an alignment problem. Did you check the fluid in the tranny?

[josh]

might be a stupid ? but make sure it is not coming from the speakers! A bad groud can make that sound. Some times it's not noticeable until the rpm's are up.

[Mikeski]

My mechanical intuition says check the fuel pump. Some injectors also make lots of noise.

[rleinen79]

After having the boat at 3 different Nautique dealers, and being blown off at each one, I found a guy who recently opened his own marina. He used to work for a Nautique dealer, and is PCM certified. He took it out on the water, and within 5 minutes, SURPRISE! problem found. It turns out that the packing coupler was rubbing on the drive shaft at times. He replaced it with and OJ shaft seal, with watercooled seals, and assured me that they would prevent it from happening again. He was in awe that the other dealers couldn't find the problem. The good news is, I took the boat out, and the noise and vibration is completely gone! Sometimes you can't beat going to the "little man" instead of the "big dog". The other dealers all said it was "something in the transmission", it was "normal", it was "not hurting anything to run it that way". So a big thanks to Starboard Choice Marine in Mishawaka IN.

[SGY]

Nice work in finding a good mechanic. There's raging incompetence out there.