Help diagnose a sound?

69fastback

I've been looking for the cause of this for a few years. It's very intermittent, and only happens on start up. After the engine has been running for 10-15 seconds it stops, and it only does it at idle, but it'll make the noise regardless of in gear, or out of gear. When we were out yesterday it only did it once, but sometimes it'll do numerous times. It's random and intermittent. The noise is coming from the rear of the engine, ie....not a belt or idler pulley. It's been happening for a few years, and since I've first heard the noise, both the entire transom assembly, and outdrive have been replaced, and it's still here. So basically, everything behind the motor is new, and it was doing it before all that was replaced. Any ideas?

https://m.youtube.com/watch?v=EfDamwbIQgc

Handymans342

Thats a dry bearing. Alternator. You could try to remove the belt and run for 20 seconds

69fastback

Alternator was recently rebuilt as well. It's definitely coming from the rear of the engine, but I can try it without the belt. The problem is, if it doesn't do it without the belt on it doesn't really mean anything, because it doesn't always do it. 

F1100

sounds like belt related squeel

raybo3

Power steering pump???? I hate to say this but I agree with Handy (lol) sounds like a bearing.........

LaRea

A mechanic stethoscope might be helpful, although that can be a challenge with intermittent problems.  I get the impression you use the boat a lot, right?  It's hard to think that a failing bearing would last for a few years of regular use.  

LaRea

$4 at Harbor Freight.  How do they do that?

https://www.harborfreight.com/mechanics-stethoscope-69913.html

randy56

x2 on power steering pump? water pump, alternator, if you think it's coming from the rear, did you grease your gimble bearing, there are two grease fittings, you only have to get to one of them to grease it. 

69fastback

I agree it sounds like a bearing but there’s no question that it’s coming from the back.  Gimbal was greased. The zerk that’s in the bellhousing was also greased. 

69fastback

LaRea said:

$4 at Harbor Freight.  How do they do that?

https://www.harborfreight.com/mechanics-stethoscope-69913.html

I have ave one of those but I’ve never been quick enough to catch it since it doesn’t always do it, and it doesn’t do it for very long. That video is about the longest I’ve ever heard it do it. Lol

69fastback

LaRea said:

A mechanic stethoscope might be helpful, although that can be a challenge with intermittent problems.  I get the impression you use the boat a lot, right?  It's hard to think that a failing bearing would last for a few years of regular use.  

And that’s the other thing. We do use it a lot, and I told my wife that whenever tbis part fails, I want another just like it because this stupid thing has been doing this for 3 or 4 years and it hasn’t quit yet!  Lol. 

When my race car starts having an issue we can’t figure out, I always say “let’s go make a nitrous hit and we will figure it out.”  I tell my wife we will figure out what it is when it fails, but it keeps going. 

Handymans342

Dont worry about it .Whatever it is will fail then you will know what it was

reneechris14

That's the blower fan cheap and easy fix. Definitely have heared that sound before. 

aero3113

I was going to say the blower also. 

reneechris14

You hit the blower switch off and the sound will stop. Lol 

69fastback

Hmmmm well, so using skiing as an example, I leave the bilge blower running the whole time as we are changing skiers and shutting the motor down, and it only does it right after I start the engine. The next time out I’ll take my stethoscope and have the hatch open and ready, and have my wife start the boat. It’s always annoyed me, but now I’m on a mission to figure it out. 

aero3113

When you do hear it, give the blower a couple of good hits with your hand to see if the sound changes pitch.

69fastback

Ok I’ll do it. 

Or or I can just not use the blower anymore HA!

Black_Diamond

+++ on the blower. Beware distorting the blower frame when screwing it down or fastening on the blower hose too.  Easy to do and will cause the fan to hit the housing. 

reneechris14

But if don't use the blower you can't use the boat. Now that would just suck. Lol

Stodge

You have 2 more bearings to consider.  The idler and tensioner pulleys are just bearings with plastic wheels on them.  Had one fail without warning.  They run about $30 each.  I think you could pull the belt and turn them to see if they move smoothly.  Being mine were 15+ years old I just replaced all of them when 1 failed.

69fastback

Well, it’s not the blower because I turned it off and the noise continued. 

dalek

To my old ears, that sound is of something rotating much faster than the engine itself. Definitely up in the Khz.
If your sure it's from the back end.
Pinion return spring or sticky pinion on starter maybe?

Wildboating

Is the coupler slipping on the rubber, gets a little friction and heats up/stops?  It is located directly behind the engine.

69fastback

Wildboating said:

Is the coupler slipping on the rubber, gets a little friction and heats up/stops?  It is located directly behind the engine.

Is there a way I can check that?

Wildboating

@69fastback
Have you ever noticed you feel like you are not getting as much speed as you used too, or if you get on the throttles hard to you hear that noise?

69fastback

Wildboating said:

@69fastback
Have you ever noticed you feel like you are not getting as much speed as you used too, or if you get on the throttles hard to you hear that noise?

I never hear the noise under throttle. I rarely ever have the boat at top speed. Ever. There’s just no need, but I did make an impromptu speed run today, and only got 47 MPH out of it, which is low, but it had a lot of gas, the lake was choppy, and he wind was blowing. 

aero3113

47 MPH is low??

Handymans342

Could be air or fluid going thru the power steering assist unit 

69fastback

aero3113 said:

47 MPH is low??

Yeah. Any time I’m feeling frisky and run it out, it’s usually 53-55 MPH. This is about how I normally cruise around. 

Handymans342 said:

Could be air or fluid going thru the power steering assist unit 

I did have to replace a power steering hose last year.

Handymans342

Thays the only other item towards the rear