89' 3.7 mercruiser screeching noise

[RCrockett]

I am newbie, but am learning. I hope someone here can give me a direction to go. I am at a loss where to turn at the moment.

I got a 1989 Wellcraft with a 3.7 mercruiser and an Alpha one drive unit. I can hear the groans over my motor already. But, I was told the motor had been gone through but I checked a lot anyway. First outing it would not idle and stalled and left me stranded. Urgh...Water in the fuel...I added seafoam and cracked open the carb to clean it out. Lots of crap in the carb. got it back together and it runs real good. Second outing we cruised down the lake at just above an idle till fluid levels were normal. Went to 3/4 throttle and was running great! after about 5 minutes it started getting loud rapping noise. I slowed down and turned back towards the marina. About half way back the rapping turned to a screeching noise. i slowed down further and prayed to get back to the marina. Nope, everything shut down about a mile away. Had to get towed again.

I know the screeching noise was not good, but cant seem to find out what it was. The next morning i went out and turned the key and it turned over. I pulled the drive unit off thinking maybe a gimble bearing or the U-joints, they looked good. i took the top cover of the drive unit off and all looks good there too. I can put it in gear and rotate the prop and all the gears move fine. With the drive unit off, i hit the key and it wanted to fire up. I am back to thinking it was something in the engine but I am not sure where to start.


I put everything back together and tried to start it up and it wants start but doesn't catch. That is where i left it last night. any help will be appreciated.

Roy

 

[Don S]

Re: 89' 3.7 mercruiser help

Re: 89' 3.7 mercruiser help

Second outing we cruised down the lake at just above an idle till fluid levels were normal.

Not sure what you are referring too there, what fluid levels do you have to run to get to normal?

Have you checked the engine oil?

 

[RCrockett]

Re: 89' 3.7 mercruiser help

Re: 89' 3.7 mercruiser help

when I first start the boat the oil pressure is a little high and the engine temp is low. I cruised until the oil pressure dropped from 80 down to about 50 and the engine temps came up to 120 or so.

 

[RCrockett]

Re: 89' 3.7 mercruiser help

Re: 89' 3.7 mercruiser help

I just did a compression check on the front 3 cylinders and they are all around 140. I can't get the back plug out, the anti freeze tank is in the way. I am trying to figure out how to to that at the moment.

The screeching noise is making me think a bearing, but I don't know. Everything is turning over fine at the moment. But, it will not start now. It keeps acting like it wants to, but wont. I am hoping to get it going so we can enjoy the rest of the season before I have to do the floor and stringers.

 

[RCrockett]

Re: 89' 3.7 mercruiser help

Re: 89' 3.7 mercruiser help

Ok, I got the motor running and found the squeaking/screeching noise WAS coming from the motor. somewhere deep inside the motor.

The big question I have now is...Do I rebuild or replace this motor? If I replace can i replace it with another motor? like maybe the 4.3 v6?

I have to replace the floor and most likely the stringers...and motor mounts...and probably the transom. This is going to be a MUCH bigger job than I anticipated.

 

[Don S]

Re: 89' 3.7 mercruiser help

Re: 89' 3.7 mercruiser help

The big question I have now is...Do I rebuild or replace this motor?

Take it apart and inspect. Only way you will know for sure. It may not be rebuildable.

 

[RCrockett]

Re: 89' 3.7 mercruiser help

Re: 89' 3.7 mercruiser help

thank you very much Don. I got this boat knowing that a complete floor rebuild was in its future. Now I am facing the motor problems...I am struggling with the realization that my work load has just doubled. Now my big decision is...is this boat worth it? My gut is saying yes but head is saying no. Thanks again for the help above.

 

[RCrockett]

Re: 89' 3.7 mercruiser help

Re: 89' 3.7 mercruiser help

Ok I pulled the motor and hooked it up to an engine stand...

We dropped the oil pan and looked inside and....Everything looks good. grrrr!
The bearings are showing some wear but nothing seroius. There are not and chunks of metal, everything looks good. We did find chuncks of magnet all over the place on the front of the oil pan...Could that have made the screeching noise and stopped the motor?

 

[Eric 3.7LX Alpha 1]

Re: 89' 3.7 mercruiser help

Re: 89' 3.7 mercruiser help

Yes the magnets could have stopped the engine from turning.

 

[RCrockett]

Re: 89' 3.7 mercruiser help

Re: 89' 3.7 mercruiser help

I think this might have been my problem.

I found all of this in pieces inside of the stator assembly.I will be getting an alternator to replace the cahrging system. If I take all of the magnets out will the motor run ok? should i remove the other half of the stator assembly as well?

 

[fmalott]

Re: 89' 3.7 mercruiser help

Re: 89' 3.7 mercruiser help

no you will need another used one it's also called balancer so it needs to be balanced just like a car harmonic balancer the magnets act as a balancer also. when you convert to alternator throw out the stator and replace balancer with magnets

 

[stonyloam]

Re: 89' 3.7 mercruiser help

Re: 89' 3.7 mercruiser help

What I would do is remove the other magnets from the rotor and take it to a machine shop and see if they can check the balance and rebalance it if necessary. Yes remove what is left of the stator.

 

[fmalott]

Re: 89' 3.7 mercruiser help

Re: 89' 3.7 mercruiser help

What I would do is remove the other magnets from the rotor and take it to a machine shop and see if they can check the balance and rebalance it if necessary. Yes remove what is left of the stator.

hopefully there is no damage to the crank shaft

 

[RCrockett]

Re: 89' 3.7 mercruiser help

Re: 89' 3.7 mercruiser help

I finally got a chance to check out all of the bearings. This is what i found when I pulled the #2 Connecting rod. No bearing??

As you can hopefully see the end of the bearing is sticking out. I turned the #2 rod bearing. I will be taking out the crankshaft and taking it to a machine shop to see how bad i messed it up. I will also take the balancer and to have them check that out as well. What about the rod? does that need to go as well?

 

[stonyloam]

Re: 89' 3.7 mercruiser help

Re: 89' 3.7 mercruiser help

If you spun the bearing, you will need a new rod. I think they are Ford 460 rods but am not sure. I have read that they have a ford number on them. your machine shop guy should be able to tell you. At this point you may want to go for a full rebuild. Should be good for another 30 years or so. Good luck.

 

[RCrockett]

Re: 89' 3.7 mercruiser help

Re: 89' 3.7 mercruiser help

Thanks stonyloam, My brother in law was telling me the same thing. He said "you are that close you might as well rebuild all of it". So that is what I am going to do. I did some research and the 3.7 uses the same pistons, connecting rods, and heads as the Ford 460. I thought that would make it easier to find, but there are several different rods out there. I guess I just need to get one out so i can see which one I need. If I replace one, should they all be replaced? Should I replace the pistons as well? I see most rebuild kits come with pistons too. Any recommendations? Should I stay with sierra and quicksilver or go with another brand from the many car companies? I wish I would have paid more attention in shop class!! decisions decisions decisions.

 

[stonyloam]

Re: 89' 3.7 mercruiser help

Re: 89' 3.7 mercruiser help

Thanks stonyloam, My brother in law was telling me the same thing. He said "you are that close you might as well rebuild all of it". So that is what I am going to do. I did some research and the 3.7 uses the same pistons, connecting rods, and heads as the Ford 460. I thought that would make it easier to find, but there are several different rods out there. I guess I just need to get one out so i can see which one I need. If I replace one, should they all be replaced? Should I replace the pistons as well? I see most rebuild kits come with pistons too. Any recommendations? Should I stay with sierra and quicksilver or go with another brand from the many car companies? I wish I would have paid more attention in shop class!! decisions decisions decisions.

Been a long time since I rebuilt an engine, so it would be best to talk with your machine shop, see what they think. One important thing IMHO is to go with a OEM Mercruiser head gasket (even though the engine kit will have a head gasket). They are designed specifically for the 470, and seal better than aftermarket gaskets.

 

[Eric 3.7LX Alpha 1]

Re: 89' 3.7 mercruiser help

Re: 89' 3.7 mercruiser help

I would bring it in to the machine shop, let them look at it and tell you what you need. That may not be the only damaged one, you didn't mention if you checked them all?

They may even have the rod you need at their shop, or a place you can get them from. If not they can tell you what length you need to get.

You can try places like summitracing.com or jegs, they are more of a performance place but they most likely have stock replacement parts as well.

 

[NHGuy]

Re: 89' 3.7 mercruiser help

Re: 89' 3.7 mercruiser help

No bearing half, what the heck? You gotta tell us what the motor guy says to that. Is it possible it's in that pile of magnet parts?

 

[stonyloam]

Re: 89' 3.7 mercruiser help

Re: 89' 3.7 mercruiser help

No bearing half, what the heck? You gotta tell us what the motor guy says to that. Is it possible it's in that pile of magnet parts?

Sometimes when it gets loose one half of the bearing will slide around and wind up on top of the other half, I suspect that is what happened here.