Engine Noise

[nwboater45]

I just bought a 1989 Blue Water with a 3.7 Mercruiser 165 with an Alpha 1 drive. I have gone through the boat and done some basic maintenance items like replace all fuel filters, oil, and plugs / cap / wires. The compression is 160, 150, 150, 160, I have not checked it since the new oil and I checked it when the engine was cold. Anyways the boats starts right up and runs and idles fine. Besides from getting real hot (other issue I need to deal with) there is a noise that sound like it is coming from the rear of the engine. It sounds like a broken bearing noise. Kind of like when a wheel bearing goes out. That is the best way I can desribe it. It doesn't sound like metal knocking of metal. Any ideas?

Thanks.

 

[QC]

Re: Engine Noise

Welcome aboard nor'wester!!

I am going to head off the inevitable here, because we are really nice people, but 470's (3.7) bring out some emotion. Just the way it is, sorry, but they are not well liked. The reasons are many, and if there is a serious problem (sounds like you have more than one), and you really love the hull it's in, then repower (replacement with something else) may be the most common recommendation here.

Do some reading up here on 470's. Please know responses here come from a LOT of experience, and are intended to be helpful, but 470s have many issues. People that are trying to be helpful will sound like they are closing the door before it is all they way open. Please trust us. We want you here, and we want to help you love your boat, but you are starting with some steep swells in your way

Bluewater, good. Alpha, good. 470, errrrr, see above.

 

[Grub54891]

Re: Engine Noise

Sound's like a gimble bearing growling to me,or it could be a u-joint. Did you pull the drive,change the lower unit oil,replace the impeller,and service the u- joints,and check the gimble? Put the shifter in forward,pull the pin on the trim ram's and remove the 6 nut's attaching the drive and have a look in there. Also check all the bellow's while in there for crack's, weather checking and replace if they are bad. It's also recommended to change the lower shift cable at that time too.
Grub.

 

[QC]

Re: Engine Noise

Despite my comments, could easily be in the drive depending on where you are hearing the noise. I assumed rear of engine, meant rear of engine. Have you owned a stern drive before?

 

[nwboater45]

Re: Engine Noise

Thanks for the comments. I put a stethoscope on the motor tonight. As far as I can tell the valve train sounds fine and and so does the lower end. It was tough to get a clear signal from the back of the engine. Since it heats up to 200 I cannot get a scope on it long enough. Time to tackle the cooling issue first so on to a new thread.

 

[nwboater45]

Re: Engine Noise

Sorry, I should have added that when I changed the oil it looked fine. No milkly look or evidence of water. I also took the oil filter and cut the top off. There is no metal flakes in the filter. Just an old habit from when I raced cars.

 

[Bondo]

Re: Engine Noise

Thanks for the comments. I put a stethoscope on the motor tonight. As far as I can tell the valve train sounds fine and and so does the lower end. It was tough to get a clear signal from the back of the engine. Since it heats up to 200 I cannot get a scope on it long enough. Time to tackle the cooling issue first so on to a new thread.

Ayuh,.... Pull the drive, 'n see if the noise is still there....

Atleast you'll know Where to keep lookin'...

 

[NHGuy]

Re: Engine Noise

Exactly, and when you have the drive off you can stick your fingers in the gimbal bearing to feel for smooth. I hope it's that, they are easier to change than the drive bearings.

 

[nwboater45]

Re: Engine Noise

Time for an update. After building a nice little outdrive stand I got the outdrive off. After digging trough the grease pile
I found the bearing. My guess is the inside ring is not suppose to move around and when you spin it should not make any noises or feel the bearings inside. So I think that was my problem. Now to get that replaced and the heat exhanger repaired then I should be good to go.

 

[stonyloam]

Re: Engine Noise

Actually the inside of the bearing is supposed to move around, it is after all a gimbal bearing. More importantly, have you replaced the impeller in the outdrive water pump. That is most likely the cause of the overhearing. Since this is a new to you boat I would suggest replacing the impeller and the housing with OEM Mercruiser parts. You will need an alignment tool before you reinstal the outdrive, look in e-bqy. good luck