merc 650

I have a 650 merc outboard(1971) which i just got. I was decarbing it with a flush kit and I guess the water pump went. When launched later that day I noticed no water out of the pee hole. By the time I got back to the launch(it ran less than about 6 or 7 minutes) I guess it overheated. The motor runs but is rough. Checked compression and got 125 on bottom 3 cylinders but only 15 on top cyl. Tried dextran ATF in the cylinder but didn't free the rings. I guess I'll have to tear it down and replace rings/piston or possible rehoned cyl. Is this something I can do myself? I have some experience with 2 cylce snowmobile and cycle engines. It looks pretty complicated. Do I need special tools to compress rings when reassembling powerhead?

Re: merc 650

Welcome to the forum!<br />Just cut the bottom off a tin can and make a straight slice from top to bottom. Stick a large hose clamp over that and now you have a ring compressor.<br />15psi is not good though. You can open it up and take a look, you might just get lucky, but don't be shocked if you end up shopping for a new powerhead. You can get a general idea by opening the inspection plates on the starboard side of the powerhead (3 bolts each, one covers top two, the other the bottom two)<br />Eric

Re: merc 650

Its for sure Eric has never torn a Mercury engine down. The pistions and crank assm. go in from the back that makes it tough to use the tin can, the factory makes ring compressers that reach around the crank and rods to compress the rings. As far as telling you if you can do the job a do not know your experance, you need to get a manual and read it then make that call yourself--Bob

Re: merc 650

I have rebuilt an outboard almost identical to this, a 1972 Merc 500 and I still can't see why the tin can idea wouldn't work. I had borrowed ring compressors from my friend and they were really nice, clamps that reach around, but since then my dad came home and told me I coulda just used tin cans. Why wouldn't they work? <br /> http://www.shareaproject.com/fullImages/1562.jpg

Re: merc 650

He!!, screwdrivers will work, have had to use them before but it's lousy advice to give someone who asks a question, because they don't know---Bob