Been trying to diagnose a cooling issue on my Mercruiser 5.7L alpha 1 gen 1 closed cooling. Changed impeller and sea water pump, opened up all lines on the raw water and coolant sides to check for blockages, everything is fine. Had heat exchanger boiled/rebuilt at local radiator shop. Replaced 140 degree thermostat.
Still overheating.
All along I've had good flow out of the prop, but I'd describe the flow out of the exhaust as decent (at best). Pulled the riser and both sides basically looked like the attached photo. In an effort to make 100% sure that the root cause of the issue is manifolds/risers, I cleaned the visible part of the riser and manifold with a pick and it appears pretty open at this point. Note that I do NOT plan on re-using, I was just trying to confirm that the problem is isolated to the manifolds and risers before I drop $800 on parts. I put everything back together and now I get very little flow out the exhaust, even more is "shooting" out the prop, and I'm overheating.
Is my logic flawed here that I could mechanically "clean" the risers and manifolds to isolate my problem?
Any education is appreciated here,
Still overheating.
All along I've had good flow out of the prop, but I'd describe the flow out of the exhaust as decent (at best). Pulled the riser and both sides basically looked like the attached photo. In an effort to make 100% sure that the root cause of the issue is manifolds/risers, I cleaned the visible part of the riser and manifold with a pick and it appears pretty open at this point. Note that I do NOT plan on re-using, I was just trying to confirm that the problem is isolated to the manifolds and risers before I drop $800 on parts. I put everything back together and now I get very little flow out the exhaust, even more is "shooting" out the prop, and I'm overheating.
Is my logic flawed here that I could mechanically "clean" the risers and manifolds to isolate my problem?
Any education is appreciated here,
Attachments
Last edited:
