ThetaChi12
Recruit
- Joined
- May 13, 2021
- Messages
- 4
Hey all,
I ran my 1989 Merc 5.7 Alpha One this morning after my post winter maintenance and noticed a little bit of smoke/steam rising from the starboard side of the intake manifold. This was after running it pretty hard for 5-10 min, with the boat running great and everything seemingly normal. Engine temp gauge and top of the thermostat housing readings were right where they should be (~160-168F), but the topside middle of the intake manifold on both sides (just below the carburetor, between the 4 & 6 cylinder markings on the starboard side and the 3&5 cylinder markings on the port side were HOT....I mean very hot! My IR thermometer showed as high as 388F!
I took a bunch of temp readings when I got back to the dock at idle, which were:
Top of thermostat housing - 164F
Thermostat raw water bypass - 68F
#1 Cylinder Marking on Intake Manifold - 169F
#3 Cylinder Marking - 166F
#5 Cylinder Marking - 190F
#7 Cylinder Marking - 160F
#2 Cylinder Marking - 160F
#4 Cylinder Marking - 158F
#6 Cylinder Marking - 187F
#8 Cylinder Marking - 177F
Topside gap between 4&6 on starboard side - 255F
Topside gap between 5&7 on port side - 260F
These middle areas on the topside of the intake manifold below the carburetor also have significantly more corrosion than other areas.
The exhaust manifolds and exhaust risers on each side seemed fine, with temps in the ~170 range at the highest as I recall. I took these apart and cleared out some corrosion about a year and a half ago. I get good system flow through the exhausts and prop when I run up on muffs.
I've been doing all my own maintenance for a few years now after some bad experiences with local mechanics, and I've learned a ton. But I don't have a clue about this one. Is it normal for these sections on the topside of the engine to have such high localized temps? Sure wouldn't seem so, but I'm learning here. Thanks.
I ran my 1989 Merc 5.7 Alpha One this morning after my post winter maintenance and noticed a little bit of smoke/steam rising from the starboard side of the intake manifold. This was after running it pretty hard for 5-10 min, with the boat running great and everything seemingly normal. Engine temp gauge and top of the thermostat housing readings were right where they should be (~160-168F), but the topside middle of the intake manifold on both sides (just below the carburetor, between the 4 & 6 cylinder markings on the starboard side and the 3&5 cylinder markings on the port side were HOT....I mean very hot! My IR thermometer showed as high as 388F!
I took a bunch of temp readings when I got back to the dock at idle, which were:
Top of thermostat housing - 164F
Thermostat raw water bypass - 68F
#1 Cylinder Marking on Intake Manifold - 169F
#3 Cylinder Marking - 166F
#5 Cylinder Marking - 190F
#7 Cylinder Marking - 160F
#2 Cylinder Marking - 160F
#4 Cylinder Marking - 158F
#6 Cylinder Marking - 187F
#8 Cylinder Marking - 177F
Topside gap between 4&6 on starboard side - 255F
Topside gap between 5&7 on port side - 260F
These middle areas on the topside of the intake manifold below the carburetor also have significantly more corrosion than other areas.
The exhaust manifolds and exhaust risers on each side seemed fine, with temps in the ~170 range at the highest as I recall. I took these apart and cleared out some corrosion about a year and a half ago. I get good system flow through the exhausts and prop when I run up on muffs.
I've been doing all my own maintenance for a few years now after some bad experiences with local mechanics, and I've learned a ton. But I don't have a clue about this one. Is it normal for these sections on the topside of the engine to have such high localized temps? Sure wouldn't seem so, but I'm learning here. Thanks.
