What do I need to know - Mercruiser 3.7

river newbie

New Member
Jul 27, 2010
Boat Info
1987 Sea Ray Seville BR
Mercruiser 3.7 Alpha
I just got an 87 Seville and trailer for the cost of a trailer and now I am assessing the repairablilty of the boat. It had a carb fire and the floor around the ski locker is rotten but I have a carb and I can fix the floor (don't know how bad the stringers are yet) but I was surprised to see that it has a 3.7 instead of a 3.0. What should I know about this engine? The oil and coolant are clean and the heat exchanger and manifold look good. I want to vacuum out the intake manifold (fire put out with dry chemical extinguisher) before I check the compression - should I take any other precautions? What about Seafoam or penetrating oil in the cylinders before I turn it over? Presuming everything is OK and it runs as it should, does this half-of-a-V8 from Ford have any quirks or weak spots?
Not from Ford. That is a Mercruiser engine with aluminum heads. Supposedly the same head which would go on one side of a Ford 460 big block, but I do not know that for sure. Great torque and fuel economy. Some will say parts are heard to come by, but only because they haven't looked hard. 2 mods it should have, though, are conversion of the magneto-type charging system [like on an outboard] to an alternator [$250-350] and a 4 inch heat exchanger [earlier versions came with a 3 inch exchanger]. Also, make sure you regularly change the anode for the heat exchanger since you have an iron block and aluminum heads.
if it hasn't been operated in a while [more than a few months] remove the plugs and spray a mist of penetrating oil in each cylinder.
If it was running when the dry chem was spayed in, then change the oild and filter, remove the intake and clean it thoroughly, and pray.
If it runs OK, change the oil and filter again after a couple of hours run time.
Thanks for the response! The PO said it died before the fire was extinguished and, yes, it has been sitting for about four months - I will change the oil, fog the cylinders, and pull the intake just in case. Where in the HX is the anode? Also, are these anodes readily available? The PO also claimed the alternator works fine but that is certainly an ugly beast isn't it?
Don't forget to pray...

The anode in the heat exchanger will be a pencil anode. It looks like a bronze-headed bolt going into the exchanger somewhere. Just google "pencil zinc" and you can find pictures. Pencil anodes are standard parts at any marine supply.
Thanks! The HX is 4 inches so that is one less change to consider. I will get the intake off this week and hope to know more about what I have in store.

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