Ok… here’s the port side and a better look at the pistons after cleaning the crud off them a bit.
Clearly a tuliped valve in the middle port side as well. Looks like the valve on the left has some corrosion going on as well.
Here’s my options:
A. Bring the cylinder heads in to be redone and...
Ok… I’m in deep now… got the starboard side pulled apart tonight. Will pull the valves on the problem cylinder tomorrow or this weekend.
Yesterday I repeated compression test on this cylinder (farthest right) after squirting some oil into the cylinder to see if it might be a piston/ring...
Not bad guesses…
Was a saltwater boat but has been in freshwater only since 2019. I had the port manifold off and didn’t see anything remarkable… gaskets were intact. I replaced the manifolds and risers several years ago.
It has never seen freezing temps (stored in heated shop).
The issue...
Ok… compression test results (wish I would have done this sooner). Pretty clear where the problem lies.
Cylinder 1: 165
Cylinder 3: 20 (barely moved the needle)
Cylinder 5: 170
Cylinder 2: 20 (barely moved the needle)
Cylinder 4: 180
Cylinder 6: 180
What are the possibilities? Stuck...
100% sure I was measuring #1 cylinder and honestly I was surprised to find that the mark is in fact at top dead center. I was convinced that the mark was off. I replaced the balancer about a year ago also.
What’s my next move?
Engine: 2000 Mercruiser 4.3LH 500+ hours thunderbolt 5 ignition. Weber 4 bbl carb.
Issue: mid summer the engine started bogging at higher rpms and while accelerating under load and would backfire through carb if accelerating too fast. Worse while engine was cool, but...
1998 Mercruiser model MCM 4.3 LH S/N 0L690518 I'm having an intermittent stalling issue that is the result of a lack of voltage to the fuel pump through the oil pressure safety switch circuit. I've been working on this issue for a while, and being intermittent, it has been difficult to...
