I just purchased a 2007 openbow with a 4.3 Mercruiser that supposedly threw a rod. I picked up the boat very discounted as it was assumed it needed a new engine. The owner told me he was driving it last season and it started making a bunch of clunking noises and running rough. He shut it down and trailered it to his Marina to be looked at. They told him it threw a rod and would need a new engine. Since it was at the end of the season he just had it winterized and put it away. This spring he just decided to sell it and be done as a boat owner.
I went to start prepping the engine to be pulled last night and found it did not throw a rod. I checked the oil before I went to drain it and it looked good. So I started poking around. It spins over fine and holds 40 psi of oil pressure while the starter is spinning the engine. I did two compression tests as I forgot to open the throttle on the first one. I would say it just has a bad valve on #4 if it wasn't for the #1 and #3 readings. They are making me think that there is either two separate issues or something going on that I don't know about. I did throw some PB Blaster lube into the #4 cylinder and it made no difference in psi. My thoughts on the generally lower #'s the following day is that after being winterized, there was probably some oil helping to seal things up a bit the first time. The unburned fuel from that first test probably washed the cylinder walls down by the next day.
Any help or advice for next steps is greatly appreciated. Thanks!
Compression Test results:
Closed throttle: 1-185, 3-190, 5-220, 2-210, 4-145, 6-215
Open throttle (The next day): 1-190, 3-180, 5-210, 2-210, 4-125, 6-210
I have pics of each spark plug here:
https://picasaweb.google.com/114579740097571480529/43Engine
I went to start prepping the engine to be pulled last night and found it did not throw a rod. I checked the oil before I went to drain it and it looked good. So I started poking around. It spins over fine and holds 40 psi of oil pressure while the starter is spinning the engine. I did two compression tests as I forgot to open the throttle on the first one. I would say it just has a bad valve on #4 if it wasn't for the #1 and #3 readings. They are making me think that there is either two separate issues or something going on that I don't know about. I did throw some PB Blaster lube into the #4 cylinder and it made no difference in psi. My thoughts on the generally lower #'s the following day is that after being winterized, there was probably some oil helping to seal things up a bit the first time. The unburned fuel from that first test probably washed the cylinder walls down by the next day.
Any help or advice for next steps is greatly appreciated. Thanks!
Compression Test results:
Closed throttle: 1-185, 3-190, 5-220, 2-210, 4-145, 6-215
Open throttle (The next day): 1-190, 3-180, 5-210, 2-210, 4-125, 6-210
I have pics of each spark plug here:
https://picasaweb.google.com/114579740097571480529/43Engine
