Mercruiser 5.7 Manifold Temps

[bigjohn57ebay]

Hello All, I have a 1991 220 Sundancer with a 5.7 Raw Water cooled with a Alpha 1 gen 2 drive that is running a little Hot Lately. The Gauge indicated about 170F at idle and slow speeds. then climbs to 195 at full throttle. I used a inferred Thermometer and the Port Manifold was running 85-90F and the Starboard manifold was running 135-140F. Is it normal for one manifold to run 45-50F higher? Any manifold troubleshooting would help. I am a Aircraft and Auto Mechanic,but new to Marine Maintenance. Also what is a normal operating temp for a 2002 5.7 Mercruiser raw water cooled with a Alpha 1 gen 2 drive? Thanks for any input.

John Filioppelli
Glen Burnie,MD:huh:

 

[mvoellinger]

The fact that there is such a large difference tells me the starboard manifold is probably blocked, which would explain why it is heating up at higher power. You should pull it off and take a look, its not that difficult to do.

 

[Amberjack01]

I have 2001 5.0 B IIIs raw water cooled. Just replaced manifolds, risers, and elbows. Port sides are in the 90s and the starboard sides are 10 to 15 degrees warmer. Feel the hoses coming out of the t-stat housings to both sides. If the temps of the hoses are correct, then the blockage is probably in the manifolds on up. If the hose temps are way off, maybe to problem is in the t-stat housing.

 

[comsnark]

You are boating in salt water. In salt water, risers and elbows are were items. If you have a 1991 boat. . you are probably due for your first, if not second, replacement. It does sound like one side is getting blocked, with disporportionate flow going to the other side.

It's been awhile since I shot temps on my risers. I seem to recall 120's-140's (yes. .there was a 20F spread). My boat has 165F thermostats installed. The two sensors (one for guage, one for alarm) are mounted near the thermostat. The IR gun on the T-stat housing will read within a few degrees of the dash gauge (one engine reads 170, the other a touch higher). Oil filter is hottest component (when things are running normal).