I was hoping to never have to place a post for overheating again. But my inline 6 is overheating on plane and the water is still cold in the bay. It gets past 160 after about a minute. Add about 3 min to that and it's getting near 180. Come off plane(didn't want to keep going) and it takes a long time for temp to come back down to about 140. The exhaust manifold and riser are running cool at all times. The hottest temp on the riser i could find with a IR gun was 143 on the outgoing side just above the rubber boot. I don't recall anything else on the water jacket areas of exhaust over 110 degrees. The exhaust ports where mated to the head were way freakin hot. Read over 300 degrees on 1 of them.
Here is what I've done so far:
Replaced water pump complete,upper,lower,impeller.(before boat was in water)
T-stat changed...twice. Housing checked for corrosion.It's ok.
Clear hose installed between incoming seawater and T-stat and another hose between T-stat housing and manifold. No bubbles in and a stream of tiny bubbles out.Ran in neutral at dock.
Checked wot at 3600. Prop will be replaced before next run.
Spark plugs are NGK BR6ES.
Briefly pulled incoming seawater hose off and it has flow and pressure. Have not done the flow test cited in the service manual yet. (15 sec at 1000 rpm while filling container)
Also checked with IR gun at temp sender and found 2 or 3 degree difference between gauge and IR.
Ignition timing adjusted and same was advancing although numbers were not compared to curves.
The water holes between the riser and manifold were open and clear prior to assembly.New riser. Manifold of unknown age previously run in fresh water. Did not cause over heat in past.
Compression between 152 & 158 on all cylinders before overheat...guess I better do this again.
No oil in water and there is oil pressure.
Ok. I think that's everything so far. It's driving me crazy. I'm going to do the flow test in the service manual although it cites a disclaimer for high speed over temp. Also going to remove the circulating pump to see if an automotive was used. Will pull the boat and check that hose between the outdrive and transom for kinks. If I can't find anything I'll double check the o-ring used when installing the drive and make sure it didn't slip out of position.
What am I missing? Could it be a bad head gasket? Water was getting into the cylinders on the hose(before launching). It was found quick and manifold changed out. It never hydro-locked. Does restricted exhaust ever run cool while on plane? From the several I've seen they were hot.I know it needs another prop but could that cause the temp to go up that quick? The engine is running great while on plane and at idle. Running even. No missing,pinging etc. Boat comes right out of the hole. I bought the engine from this guy who said the engine was rebuilt at a machine shop and then sat for about 9 years....and I was originally concerned about breaking in the cam. What do you guys think?
Here is what I've done so far:
Replaced water pump complete,upper,lower,impeller.(before boat was in water)
T-stat changed...twice. Housing checked for corrosion.It's ok.
Clear hose installed between incoming seawater and T-stat and another hose between T-stat housing and manifold. No bubbles in and a stream of tiny bubbles out.Ran in neutral at dock.
Checked wot at 3600. Prop will be replaced before next run.
Spark plugs are NGK BR6ES.
Briefly pulled incoming seawater hose off and it has flow and pressure. Have not done the flow test cited in the service manual yet. (15 sec at 1000 rpm while filling container)
Also checked with IR gun at temp sender and found 2 or 3 degree difference between gauge and IR.
Ignition timing adjusted and same was advancing although numbers were not compared to curves.
The water holes between the riser and manifold were open and clear prior to assembly.New riser. Manifold of unknown age previously run in fresh water. Did not cause over heat in past.
Compression between 152 & 158 on all cylinders before overheat...guess I better do this again.
No oil in water and there is oil pressure.
Ok. I think that's everything so far. It's driving me crazy. I'm going to do the flow test in the service manual although it cites a disclaimer for high speed over temp. Also going to remove the circulating pump to see if an automotive was used. Will pull the boat and check that hose between the outdrive and transom for kinks. If I can't find anything I'll double check the o-ring used when installing the drive and make sure it didn't slip out of position.
What am I missing? Could it be a bad head gasket? Water was getting into the cylinders on the hose(before launching). It was found quick and manifold changed out. It never hydro-locked. Does restricted exhaust ever run cool while on plane? From the several I've seen they were hot.I know it needs another prop but could that cause the temp to go up that quick? The engine is running great while on plane and at idle. Running even. No missing,pinging etc. Boat comes right out of the hole. I bought the engine from this guy who said the engine was rebuilt at a machine shop and then sat for about 9 years....and I was originally concerned about breaking in the cam. What do you guys think?
