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  #21  
Old 12-29-2008
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Strain or just high rpm?

After the boat has set awhile or comming back from a motor?

Quote:
Originally Posted by jr438234606 View Post
I've noticed that when I put a strain on my engine, I hear a strange sound. It sounds like a slight screeching/scraping sound. It's not very loud, but it still concerns me. It happens when I put the prop under considerable strain. For example, if Im moving forward and throw the engine in reverse. Or, if I power forward from stand still. I'm worried that the engine Is twisting because of the torque and possibly flexing the shaft. Could the shaft be putting too much pressure on the cutlass bearing because of this? Would the engine temporarily misalign under the load?
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Quote:
Originally Posted by ckgreenman View Post
Does it sound like a belt slipping or something?
That's usually my first thought whenever I hear a "screeching" noise from an engine space.

I would try revving the engine explosively (that's a quick, hard rev up, where you don't let the RPMs actually get very high) to see if the noise occurs when out-of-gear, too.

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  #23  
Old 12-29-2008
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Might want to check the alternator shaft for play. Belt slippage will account for the "screeching", the faint "scraping" sounds like the alt fan may be coming in contact with the housing due to excessive shaft play, or just slopping around inside loose bearings. While you are at it, get out a straight edge and check to make sure that the alternator pulley is properly aligned with the crankshaft pulley.

Last edited by bljones; 12-29-2008 at 12:59 PM.
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Old 12-29-2008
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Quote:
Originally Posted by sailingdog View Post
As CP has saidóIT WOULD HELP IF YOU MENTIONED WHAT BOAT< ENGINE AND TRANSMISSION YOU HAD when asking for assistance like this. Some engines, transmissions, and boats have known issues that are fairly common....and knowing that information makes it a lot easier to answer your question. It would also help if you said where the screeching/scraping sound is coming from.

BTW, yes, the engine can become misaligned under load since the torque put out by the engine is significant. IF you have a broken engine mount, that could allow the engine to move under load.

YOU REALLY SHOULD READ THE POST IN MY SIGNATURE, since you can't seem to figure out that more information in a post asking for help is generally better than less.
Actually, sailindDog, I know that more information is better. If you read back through posts I have initiated, you'll find that I "figured that out" a long time ago. However, since I was typing on a cell phone during a holiday party, I hope to be excused. Anyway, I'm sure you'll get over it-- you usually do.
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  #25  
Old 12-29-2008
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The engine is a brand new Yanmar 54 horse. Since a picture is worth a 1000 words, here are some pics. And YES, the engine is now aligned (unlike in the picture).

Photobucket

Photobucket

Last edited by jr438234606; 12-29-2008 at 01:24 PM.
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Old 12-29-2008
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Did you do the installation. If not, I say warranty and I would be on the Phone.
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Old 12-29-2008
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Quote:
I've noticed that when I put a strain on my engine, I hear a strange sound. It sounds like a slight screeching/scraping sound. It's not very loud, but it still concerns me. It happens when I put the prop under considerable strain. For example, if Im moving forward and throw the engine in reverse. Or, if I power forward from stand still. I'm worried that the engine Is twisting because of the torque and possibly flexing the shaft. Could the shaft be putting too much pressure on the cutlass bearing because of this? Would the engine temporarily misalign under the load?
I would normally associate a screeching sound with a belt. As this is a new engine, are you certain the water pump and alternator belts are tight enough? There should be about 1/2" of deflection with moderate finger pressure. Another way of telling if your belt is too loose is if you see a lot of belt residue (fine black dust) around that area.

You say it's a screeching/scraping sound though - that's a little confusing to me which is why I suggested earlier if you could identify the region it's coming from. That may make an "internet diagnosis" easier.

To specifically answer your questions above:

If the engine is improperly mounted, it will temporarily misalign. If this was an older engine, I would suspect the rubber component of the engine mounts were worn. The motor's torque will cause it to jump when revved. This is easy to check. Just watch the motor as someone revs the motor up. If there is an issue, you'll see it lurch noticeably.

If that is what's happening, then yes, you are at risk of damaging the cutless bearing, as well as the stuffing box and the coupling.

It looks like you modified the engine bed to accommodate the new motor. When was this done? At the install or after some period of use. How have you measured the alignment?

(I've said this before, but I'll say it again now - gorgeous boat.)
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Old 12-29-2008
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Quote:
Originally Posted by bubb2 View Post
Did you do the installation. If not, I say warranty and I would be on the Phone.
I had the same thought. I see the boat is out of the water at Sintes in your photo. Did they do the work? If so, they'll certainly make it right.

If Northshore Marine did the work, then good luck!
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Old 12-29-2008
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Thanks for that. Here is some additional info:

Engine is new.

It's more like a scraping sound. It's not a belt. I figure it must be the shaft.

It only happens when motor is under strain, in gear, not just reved up in nuetral.

Engine was perfectly aligned at install.

Engine beds are original, but with slight modification aft.

I have not done visual inspection, but plan to today.


Here are some thoughts i had:

Torque is shifting engine, shaft is eating into cutlass bearing.

Bearings in gear box are bad.

Shaft is bent slightly, and only gives a problem under heavy load.

Prop is cavitating.

Last edited by jr438234606; 12-29-2008 at 01:54 PM.
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Well, it stands to reason you'll get the most torque when the motor is in gear, so I'll stick with my suspicion of the motor mounts until you do your visual inspection and find out other wise. To be honest, though, if that's not it, I'm not sure what would cause the sound.

Another thought - Is the sound sustained when your revs are up or does it occur only when you power up. If it's sustained, I would look at the coupling, stuffing box and cutless bearing. If it occurs only at the moment you rev and then is mostly quiet, I would go back to looking hard at the mounts.
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