Evinrude V4 head warpage/acceptable tolerance

[powrguy]

I have a 1987 V4 90HP Evinrude, that over-heated by previous owner, and blew a head gasket (starboard side).

I inspected the motor, and found no piston or cylinder damage, and compression on #1 and #3 were 100psi, and on #2 zero, and on #4 60psi. Obviously, when I had pulled the head, the gasket was blown. I ordered all the parts to put it back together, inspected and rebuilt the waterpump, am replacing both t-stats, and checked for obstruction in the water passages (there was none). The boat went through some moss on the river, blocked the water intakes, and subsequently over-heated.

While at the Marine Dealer, I had them put the head on a plate, and they determined warpage of .008. They don't do machine work there. My question is what is the tolerance for flatness on a cylinder head like this? Could I put sandpaper on my cabinet saw top, and gently rotate/drag the surface and flatten it, or does it need to be machined on a Bridgeport or something to assure it's safe to use? I am afraid that trying the sanding routine might result in the head being tapered, as I have no SURE way of keeping it parallel to the two faces.


thanks

 

[Daviet]

Re: Evinrude V4 head warpage/acceptable tolerance

I use the sandpaper method all the time and have never had any problems. I would give it a try, sand until the face of the head is polished and recheck for warpage. The head gasket will allow a small amount of warpage without any problems.

 

[powrguy]

Re: Evinrude V4 head warpage/acceptable tolerance

I use the sandpaper method all the time and have never had any problems. I would give it a try, sand until the face of the head is polished and recheck for warpage. The head gasket will allow a small amount of warpage without any problems.

Is there a tolerance number on the warpage? What would it be? .004? .006?

 

[Daviet]

Re: Evinrude V4 head warpage/acceptable tolerance

There probably is, but without the manual for your engine, I don't have the specs for it. I am sure someone will come along that has information on that specific engine and ansewer your question.

 

[powrguy]

Re: Evinrude V4 head warpage/acceptable tolerance

OK, thanks.