Bad screeching sound?

[howard20138]

We are new to this boat it is a 1986 18' Bayliner with a 180 OMC inboard I am getting this horrible screeching sound if I adjust the trim while the boat is in gear and running about half throttle it will not stop unless I disengage and idle down. Does anyone have an idea as to the possible cause? Sincerely, Howard

[rasorinc]

Does your OMC outdrive lift up when under power?????????????Mine does not.
All mercs do.

[Jango]

This might be too simple of an answer, but, It sounds to me like a loose Belt ?

[howard20138]

yes it will raise and lower but the sound does not change, I thought it might be the alternator belt but it sounds a bit more metalic

[PAR]

If you're having difficulty diagnosing the difference between a trim pump and a V belt noise, then you are way out of your league. I mean no offense, most people just don't know these systems well enough to track down difficulties.

For what it's worth, the 181 GMC marine engine has a nasty habit of wearing it's V belt a lot longer then it should have to. This is because of how it's arranged, making changing it a pain in the butt, so it doesn't get changed. Most just keep adjusting it until they run out of alternator slot and then it cries like a smashed cat until you change it. Coupled with the timing cover's tendency to leak oil, the problem is compounded.

This is about the most simplest of diagnosis to perform on a boat. Push down on the belt at the longest unsupported span. If you get more then .5" of deflection before considerable resistance if felt, then the V belt is in need of adjustment or replacement.

I'd recommend you take it to a shop. A diagnoses may take just a few minutes. If you feel comfortable after knowing what's wrong, then change out what you need to or let them get their hands dirty.

[howard20138]

No insult taken ,I am pretty capable with hand tools, I used to work at a robolo dealer as a rigger. This sound is very metalic sounding in nature; not really much like a belt squeal although it is still a possibility? I appreciate all input I can get sincerely , Howard

[SteelTrawler]

I have been dealing with a severe high pitched noise at cruising rpm in a larger boat with and inboard. After conversations with the people from Soundown, I now believe it is gear noise from the transmission being transmitted to the hull, through the shaft or engine mounts. When did the noise begin? Has something in the drive train been chained?

[alan white]

Have someone spray WD 40 at the belt when you hear squealing. It will quiet down temporarily and that will at least eliminate the question of the source.

[howard20138]

My screeching sound only happens when I adjust the trim while underway

[gonzo]

It could be the gimball bearing. One way to isolate the sound is to use a hose about 3/4 to 1" will do. Put one end on your ear and the other around the noisy area. You will hear it louder where it comes from. Oh no, I am giving my professional secrets away

[howard20138]

The noise only occurs if I try to adjust my trim up while underway otherwise it seems fine