One manifold elbow hotter than the other

[harley31]

Here's my issue. I have a Mercruiser 5.7 350 Thunderbolt V I/O engine with an Alpha I Gen II O/D. The left riser/elbow gets extremely hot, but the right side does not. I replaced my water pump last winter (in the lower unit), but if it was in wrong I believe it would affect the entire engine. I removed the left riser to check for rust blockage. All looks ok, although I plan to flush it out to be sure. The hose from my engine mounted water pump to the left manifold is clear. I checked my shutter (I put a new one in last winter) but is is operating correctly. My next step is to remove my O/D to look for debris in the exhaust. My right exhaust puts out alot more water than my left. I was told to check my thermostat, since it has a spring loaded ball on each side, and one may be hanging up. Anybody else have any ideas??????????

 

[Bondo]

Re: One manifold elbow hotter than the other

Ayuh,... Welcome Aboard,...

It sounds like yer headed in the Right directions...

Water has to be coming In, 'n Able to get Out,...

 

[harley31]

Re: One manifold elbow hotter than the other

Thanks. I'm just making sure I don't forget anything before I get it all put back together.

 

[04fxdwgi]

Re: One manifold elbow hotter than the other

I had the "spring loaded" check ball going to my Port riser get stuck in the bore during driveway run before 1st launch after getting boat. Pulled it apart and cleaned the bore of scale and put it all back together and works fine now. Riser is running MUCH cooler, surprise, surprise.

 

[harley31]

Re: One manifold elbow hotter than the other

It is my starboard manifold/riser/elbow that is getting extremely hot. Since my first post I have disassembled my thermostat housing, hose to starboard manifold, starboard manifold, riser and elbow. I inspected, cleaned and ran water through all of those parts and the water had no restrictions or blockages. I ran a hose past my shutter to ensure a good flow out of my exhaust. All was good. I reassembled everything and ran the engine. At idle, with the earmuffs on the starboard elbow ran at 125 degrees while my port elbow was at about 88 degrees. I removed my thermostat today to replace it, only because I'm out of ideas. Is it possible that the starboard manifold is normal and the port one is running cooler for some unknown reason? My thermostat housing does not have the spring loaded balls like I thougt it would. Apparently, that is on the 6 cyl. engines.
Is it possible that the engine mounted water pump is somehow not operating correctly? But I don't think it would affect only the one manifold. My next step is to call a mechanic, which I'm trying to avoid unless absolutely necessary!
My only other thought is that it has run this way all along, but I just now noticed it. I'm afraid I might do some damage if I run the boat again like this.

 

[04fxdwgi]

Re: One manifold elbow hotter than the other

It is my starboard manifold/riser/elbow that is getting extremely hot. Since my first post I have disassembled my thermostat housing, hose to starboard manifold, starboard manifold, riser and elbow. I inspected, cleaned and ran water through all of those parts and the water had no restrictions or blockages. I ran a hose past my shutter to ensure a good flow out of my exhaust. All was good. I reassembled everything and ran the engine. At idle, with the earmuffs on the starboard elbow ran at 125 degrees while my port elbow was at about 88 degrees. I removed my thermostat today to replace it, only because I'm out of ideas. Is it possible that the starboard manifold is normal and the port one is running cooler for some unknown reason? My thermostat housing does not have the spring loaded balls like I thougt it would. Apparently, that is on the 6 cyl. engines.
Is it possible that the engine mounted water pump is somehow not operating correctly? But I don't think it would affect only the one manifold. My next step is to call a mechanic, which I'm trying to avoid unless absolutely necessary!
My only other thought is that it has run this way all along, but I just now noticed it. I'm afraid I might do some damage if I run the boat again like this.

My 7.4L engine has the spring loaded check balls on it, so it's not just on 6 cyl engines. The did eliminate them at some point, along with a complete housing redesign, but I don't know what that year was.

For what it's worth, the muffs I was using didn't seal on the drive leg very well, spraying water everywhere except into the water intakes, and I was over heating on the muffs too. I installed a home brewed perminent "flushing manifold" in the engine bay, eliminating need to use the muffs and that cured the overheating problem while on the hose.