Spare motor 3.7/170hp

cfelton · #1 01-31-2011, 09:13 AM

I've been looking around for a spare motor to rebuild and keep in the garage. Mercruiser does'nt make these blocks anymore. Looking on craigslist one night I found a siezed 3.7 motor for sale for 150.00 about 35 miles from home. I called and went by to look at it and was amazed at how clean it looked, so I bought it, the entire gimble, trim cylinders, shifter and cables. I got the motor home and dissambled it and found the riser had frozen and cracked letting antifreeze down into #3 and #4 cylinders. I soaked it down with Kroil oil and PB Blaster penetrating oil and let it soak for a week. Went back and cut a block of wood to fit the cylinders and tapped down on the stuck pistons freeing them up. After cleaning up the cylinders, intake and exhaust manifolds, and head and reseating all the valves I reassembled it. I squirted a little gas in the carb and it fired on up. I let it run for about 10 seconds. I guess I'll have to go back in though cause #4 cylinder only has about 55 psi. of compression. I guess I got some rings stuck in the piston or a broke compresson ring. Still for the money I got a hell of alot of parts for a small amount of cash. It really pays to keep your eyes open!

spareparts · #2 01-31-2011, 07:56 PM

try some Mercury power tune in cylinder number 4, let it soak for a while, worth a try for the price of a can

926bill · #3 02-01-2011, 05:17 AM

You got a deal on that one. I'm looking around also for a spare to rebuild but no luck. My 470 runs great but would like to have a backup, I'd hate to waist a summer because af a bad motor.

BC

cfelton · #4 02-03-2011, 09:48 PM

Yep. those blocks hard to come by cheap.The 170 in my V runs great, I just rebuilt it about 50 hours ago. I checked out my spare motor this morning and found my problem with #4 cylinder. I pulled the valve cover and checking the valve to rocker arm clearances, I found that the intake valve is not closing all the way.When I seated the valves I think that was the one that had a partialy burnt valve face.I had to use medium and fine lapping compound to seat that one. I must have taken alot off the face and seat. I guess I could shim the rocker or take alittle off the valve stem. I know they do make different length pushrods but I dont have any. What do you think Spare?

spareparts · #5 02-03-2011, 10:23 PM

probably easier to shim the rocker stand, you must have taken quite a bit of metal off to change the stem hwight by hand. they used to have a spec taken with the valve closed and the lifter depressed. I don't have a manual for those, see if you can find the spec online