Wreck Rider
Petty Officer 3rd Class
- Joined
- Aug 12, 2003
- Messages
- 98
Hi Guys
A little help please guys, my motor is sick and I want to make it feel better!
Facts first, my motor is a merc in-line 4 cylinder 2 stroke, model 850, 85 hp, vintage about '79, serial # 7071754. I bought it about three years ago, with a rebuilt power head. The boat is a 16' fibreglass bow rider, vintage about '75.
Last weekend I got the boat out for maiden voyage of the season. Charged the batteries, greased the engine fittings, checked the lower unit oil (clean), checked for oil in the gas (by colour, plus I always add it when I buy gas), checked the bilge pump and horn, then went to the ramp.
Boat started just fine (on a new tank of gas), and went like stink about 10 miles down the shore of Lake Ontario to Port Credit for lunch with my buddy Dave, then after that it went like stink back (the lake was super flat, which is very unusual on such a big lake) to the ramp and about 3 miles short of the ramp the gas ran out so I switched tanks, went like stink again but just about 100 yards short of the ramp the motor suddenly made a squeaky noise and then stopped. Tried bumping it with the starter but it wouldn't even turn over.
Dave and I paddled in to the ramp then took it home. Took the covers off and found the flywheel was not moving. Took the plugs out and saw what you would expect, four dark holes..... Wrestled with the flywheel and got it to turn again. Squirted some oil into each cylinder and turned it by hand, then bumped it with the starter, it turned easily.
I poured some of each of the three tanks of gas into shot glasses and the colour looks almost identical so I'm guessing there is oil in each of the tanks. When the gas evaporated something funny happened, two of the glasses have a yellowish residue while the third remains blue. Why? Is this a clue to my problem?
Yesterday I checked compression, on cylinders 1,2,3,4 it was 140, 145, 145, 145 psi cranking the motor as-is. The test kit said to squirt some oil into each cylinder and check again so I did, the results were then 163, 170, 165, 165 psi.
As far as I know this means there is a small amount of leakage around the rings (that?s what the oil is supposed to improve on), but not enough to worry. Cylinders are considered the same if the total difference is not more than 10 psi and not more than 25% of the highest compression.
So this test showed nothing of interest, except that the motor did tighten up right at the end of the testing, which makes me think the problem may be on the crankshaft end rather than the cylinder end. I don?t know which way to go now so I?m posting these results here to see what opinions I get.
A little help please guys, my motor is sick and I want to make it feel better!
Facts first, my motor is a merc in-line 4 cylinder 2 stroke, model 850, 85 hp, vintage about '79, serial # 7071754. I bought it about three years ago, with a rebuilt power head. The boat is a 16' fibreglass bow rider, vintage about '75.
Last weekend I got the boat out for maiden voyage of the season. Charged the batteries, greased the engine fittings, checked the lower unit oil (clean), checked for oil in the gas (by colour, plus I always add it when I buy gas), checked the bilge pump and horn, then went to the ramp.
Boat started just fine (on a new tank of gas), and went like stink about 10 miles down the shore of Lake Ontario to Port Credit for lunch with my buddy Dave, then after that it went like stink back (the lake was super flat, which is very unusual on such a big lake) to the ramp and about 3 miles short of the ramp the gas ran out so I switched tanks, went like stink again but just about 100 yards short of the ramp the motor suddenly made a squeaky noise and then stopped. Tried bumping it with the starter but it wouldn't even turn over.
Dave and I paddled in to the ramp then took it home. Took the covers off and found the flywheel was not moving. Took the plugs out and saw what you would expect, four dark holes..... Wrestled with the flywheel and got it to turn again. Squirted some oil into each cylinder and turned it by hand, then bumped it with the starter, it turned easily.
I poured some of each of the three tanks of gas into shot glasses and the colour looks almost identical so I'm guessing there is oil in each of the tanks. When the gas evaporated something funny happened, two of the glasses have a yellowish residue while the third remains blue. Why? Is this a clue to my problem?
Yesterday I checked compression, on cylinders 1,2,3,4 it was 140, 145, 145, 145 psi cranking the motor as-is. The test kit said to squirt some oil into each cylinder and check again so I did, the results were then 163, 170, 165, 165 psi.
As far as I know this means there is a small amount of leakage around the rings (that?s what the oil is supposed to improve on), but not enough to worry. Cylinders are considered the same if the total difference is not more than 10 psi and not more than 25% of the highest compression.
So this test showed nothing of interest, except that the motor did tighten up right at the end of the testing, which makes me think the problem may be on the crankshaft end rather than the cylinder end. I don?t know which way to go now so I?m posting these results here to see what opinions I get.