Rookie here... I have learned a lot on these threads and thank you all for helping me on countless issues. This is my first post.
MY BOAT
1984 Cobalt 19BR
GM 5.7L Mercruiser 260 Engine (278 hrs)
Raw Water Cooled
MY Problem and reason for this post
My temp gauge on the dash stopped working right after I changed the thermostat. As background, I took the boat out for the first time, only to find it overheating at idle, but not while at higher RPMs. I changed the impeller in the lower drive unit thinking that would be the problem. That didn't fix the problem. Next, I pulled the thermostat housing and verified that thermostat was super rusted and looked really bad. The brass sleeve was also in bad shape. I purchased the correct gaskets (according to mercruiser parts catalog), thermostat, and sleeve. After putting on the muffs, I started the engine. I was pleased to see the temperature staying at 120. However, after 20 minutes, I realized that this temperature was lower than it should be. My IR gun was showing 142 at the top of the Thermostat housing. When I turned off the engine, the gauge stayed on the same spot = gauge wasn't actually working.
The sending unit is attached to the intake manifold, not the thermostat housing. The new gasket between the intake manifold and the therm housing has 4 metal rings in them. HOWEVER, the old gasket there did NOT have these rings. From everything I read, people say it needs those metal rings on the gasket. But when it didn't have it, the gauge worked fine.
On a side note, while I had my IR gun out, I did check the exhaust manifolds and the hottest spot was pushing 206. Any additional thought on that?
MY BOAT
1984 Cobalt 19BR
GM 5.7L Mercruiser 260 Engine (278 hrs)
Raw Water Cooled
MY Problem and reason for this post
My temp gauge on the dash stopped working right after I changed the thermostat. As background, I took the boat out for the first time, only to find it overheating at idle, but not while at higher RPMs. I changed the impeller in the lower drive unit thinking that would be the problem. That didn't fix the problem. Next, I pulled the thermostat housing and verified that thermostat was super rusted and looked really bad. The brass sleeve was also in bad shape. I purchased the correct gaskets (according to mercruiser parts catalog), thermostat, and sleeve. After putting on the muffs, I started the engine. I was pleased to see the temperature staying at 120. However, after 20 minutes, I realized that this temperature was lower than it should be. My IR gun was showing 142 at the top of the Thermostat housing. When I turned off the engine, the gauge stayed on the same spot = gauge wasn't actually working.
The sending unit is attached to the intake manifold, not the thermostat housing. The new gasket between the intake manifold and the therm housing has 4 metal rings in them. HOWEVER, the old gasket there did NOT have these rings. From everything I read, people say it needs those metal rings on the gasket. But when it didn't have it, the gauge worked fine.
On a side note, while I had my IR gun out, I did check the exhaust manifolds and the hottest spot was pushing 206. Any additional thought on that?
