mercruiser 3.7 rebuild

I am starting a 3.7 rebuild to repower my 21ft 73 starcraft chieftain. I would appreciate any positive coments on this to help my along the way, I say positive because I know how some of you feel about these motors, and concidering i've already sent the block to the machine shop and various other things I have reached the point of no return on this project! I am going to address all the known issues and would just like to hear from those of you who have been down this path. One thing I'm planning to do is stud the head to help with any headgaskit issues, but any info I can get would be greatly apprieciated.

Thanks Robin

Re: mercruiser 3.7 rebuild

This should keep you out of the local bar.

Re: mercruiser 3.7 rebuild

Well I will be keeping a eye on this thred. I have a 3.7L and I realy like it. I like the power it has in a small packedge. A real good idea on the head studs. That will make it a little more stable.

I trust you have read about all the bad points of the engine right?? So you know what to work on.

I just passed up a boat with one of these in it, becouse it needed a "Water pump, or just a gasket" Well I think you all know what that is!!


So keep us updated, and pictures would be awsome also!!

Re: mercruiser 3.7 rebuild

Ayuh,...

Go up to the Adults Only section of this forum,+ download the manual that covers your motor...
They're Not assembled like most motors,+ are Very particular....

Re: mercruiser 3.7 rebuild

Have my replacement boat with a 4.3, but previously rebuilt my 470 before I could afford anything else. Hopefully your machine shop is well versed with aluminum....only 1 place in my area would touch resleeving the block, and it was a large motorcycle dealership. In addition to the seeping coolant and poorly engineered charging system, my 470 had horrible oil pressure at idle when warm. From my readings at the time, it was also a problem common to this engine. Even if your pressure wasn't bad, you might want to consider replacing the oil pump.

I'll return to my lurking......

Steve O.

Re: mercruiser 3.7 rebuild

Thanks for the info, in regard to the block I'm hoping that it can be bored to correct the imperfections. If by chance thats not the case, does anyone know just how extensive it is to resleve this block? Do the existing sleves have to be pressed out or can they be bored, then sleved?

Thanks Robin

Re: mercruiser 3.7 rebuild

cabinfever said:

I am starting a 3.7 rebuild to repower my 21ft 73 starcraft chieftain. I would appreciate any positive coments on this to help my along the way, I say positive because I know how some of you feel about these motors, and concidering i've already sent the block to the machine shop and various other things I have reached the point of no return on this project! I am going to address all the known issues and would just like to hear from those of you who have been down this path. One thing I'm planning to do is stud the head to help with any headgaskit issues, but any info I can get would be greatly apprieciated.

Thanks Robin

Click to expand...

Are you looking for a complete engine kit, Master Overhaul kit for this engine? The aftermarket suppliers do make complete to partial rebuild kits for these engines that include pistons, rings, bearings, gaskets, oil pump, cam, lifters, and timing sets. You can buy all or you can cherry pick the items you want to suit the repair of the engine.

Re: mercruiser 3.7 rebuild

The local machine shops I contacted said there was not enough tolerance left because of the damage to simply bore the sleeves out to a larger size....the one damaged cylinder had to be resleeved. They would not touch it because of the heat issue associated with the aluminum block and the heat generated removing the sleeves, hence the reason I went to the motorcycle shop. That left me with instead of trying to have all 4 bored out, since I had just blown a hole in the #3 piston, I only had the one cylinder resleeved. $250 later new sleeve in 3, the others "cleaned up" the block was ready to go.

Sorry I cannot tell you how far over hey can bore them out since I did not end up going that route. Hope it all works out in your favor....

Steve O.

Re: mercruiser 3.7 rebuild

cabinfever said:

i've already sent the block to the machine shop and various other things I have reached the point of no return on this project!

Click to expand...

It's sounds like a poker game where you already have too much money in the pot to fold now.

cabinfever said:

in regard to the block I'm hoping that it can be bored to correct the imperfections. If by chance thats not the case, does anyone know just how extensive it is to resleve this block? Do the existing sleves have to be pressed out or can they be bored, then sleved?

Click to expand...

I have rebuilt several engines, but never one of these, so I cannot be too much help on the specifics... sorry.

But I CAN say that many of the questions you are asking can really only be answered by the machine shop you already have the block at - you need to get the answers about how much to bore and whether or not to resleeve from them. If they can't answer the questions, then you need to find another shop who can.

Re: mercruiser 3.7 rebuild

I'm also in the process of rebuilding my 470. I like the idea of using studs for the head. I replaced the stock rocker arms with rollers and also went with a stud kit to eliminate the special length push rods and shimming the stock rocker arms. My engine was siezed and pretty badly corroded, the machine shop in my area ,who has a fair amount of experience with this engine, sucessfully bored my block out to .060" over bore and there was plenty of metal to work with. I also found what I thought was a good deal on a rebuild kit on E-Bay http://www.internalengineparts.com it has all name brand components, gaskets,rings, main and rod bearings, pistons with pins and they can do any overbore, undersize combination you would need. I thought someone told me that the sleeves are knurled, then the block heated and the sleeves are installed. Pretty much no way to resleeve it. Hope this helps. if you have anymore questions on what I have done PM me. Also check http://www.breezeworks.net

Re: mercruiser 3.7 rebuild

I used the same site internalengineparts.com the kit was great.

Re: mercruiser 3.7 rebuild

How is the rebuild going? I think I am going to have to do the same to my 3.7L. I rebuilt the motor in my dodge dakota about a year ago, so I am hoping that it won't bee too much difficult on a mercruiser. Please if you have any insight since you have done it already. I would really like to know.

Thanks, Dan