A new impeller a couple of months ago? Is it possible they replaced it because bits of it broke off and the pieces are now lodged further down the line? I've never had that issue, but I have read about others having that happen.
3JH4E Overheating at low RPMs - Any ideas?
- Thread starter flightlead404
- Start date
Well something is seriously FUBAR here. I have hooked up an 1,100 gph bilge pump with the output of the pump going to the hose from the heat exchanger where I unhooked it from the elbow. It runs up to the siphon break, down to the heat exchanger. So a head of less than 3’ which should still be 1,000 gph. I hooked the return to my bucket onto the hose end I pulled from the output of the raw water pump. That is, its pumping (Barnacle Buster at 4:1 dilution) in reverse of normal water flow.
Or at least, it should be.
I’m getting a trickle. Literally on the order of a few teaspoons a minute output. The pump is working fine. Its a fountain when I unhook it.
This engine ran at full power for 5 minutes without showing abnormal temps anywhere in early April (I had a separate diesel survey done, temps checked with IR gun during run).
I have a new coolant pump I’ll pick up tomorrow, the current one has weep tracks below it, but right now that doesn’t look like the issue.
Or at least, it should be.
I’m getting a trickle. Literally on the order of a few teaspoons a minute output. The pump is working fine. Its a fountain when I unhook it.
This engine ran at full power for 5 minutes without showing abnormal temps anywhere in early April (I had a separate diesel survey done, temps checked with IR gun during run).
I have a new coolant pump I’ll pick up tomorrow, the current one has weep tracks below it, but right now that doesn’t look like the issue.
Its slightly better in that direction, maybe a pint or so a minute. Certainly not what I’d expect from 1,100 gph pump. I’ll let it run an hour or so this way around and see what happens.
Have you checked the coolant in the actual heat exchanger, under the radiator cap? The coolant bottle can be full and the cooling system low. This usually happens because of a bad pressure cap.
Also make sure to burp the air out of the coolant side of the system. There is often a bleeder valve near the hot water heater.
From the resent posts above it sounds like you have identified a problem on the sea water side of things.
Also make sure to burp the air out of the coolant side of the system. There is often a bleeder valve near the hot water heater.
From the resent posts above it sounds like you have identified a problem on the sea water side of things.
Possibly parts of an old water pump impeller partiall clogging the inlet of the heat excjhanger?
Replaced fw pump, raw water impeller, cover plate, o ring, thermostat, pressure cap, several hoses, and ofc all new coolant properly burped. Ran it 24-2500 for 10 hours tying to make bridge openings. Ran ok, little wisps, but only one overheat when I ran up to 2,800 for 5 mins or so to pass a barge.
Sea water pump does appear to have some corrosion on it. Will probably rebuild just to do it.
I tried to blow through the heat exchanger just for grins, not easy to get much air through it. I thought from the design I s/b able blow through it easily.
Sea water pump does appear to have some corrosion on it. Will probably rebuild just to do it.
I tried to blow through the heat exchanger just for grins, not easy to get much air through it. I thought from the design I s/b able blow through it easily.
I found 4 bits of old impeller blades that the previous owner left for me. I was not having overheating issues.
My motor is different than yours but it was an easy process. Disconnect batteries, remove belt cover, remove alternator, then remove heat exchanger cover. Remove impeller bits and clean oring. Reassemble.
If you haven't already, I would use some sort of chemical flush on both systems.
My motor is different than yours but it was an easy process. Disconnect batteries, remove belt cover, remove alternator, then remove heat exchanger cover. Remove impeller bits and clean oring. Reassemble.
If you haven't already, I would use some sort of chemical flush on both systems.
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Ran the boat for essentially a week up to Brunswick at 2,300 to 2,400 making 5.8kts at .8 gph with no overheat.
I do seem to be going though a tiny bit of coolant, but need to explore that more. For now this issue is corrected, although I'll go back and IRAN various hoses etc on the motor as they look original.
Also I'm not a fine of the liberal use of pipe dope on fittings that are designed to seal mechanically. And A&P would have their ticket pulled for such transgressions. I'll get this motor up to aircraft standards this summer.
I do seem to be going though a tiny bit of coolant, but need to explore that more. For now this issue is corrected, although I'll go back and IRAN various hoses etc on the motor as they look original.
Also I'm not a fine of the liberal use of pipe dope on fittings that are designed to seal mechanically. And A&P would have their ticket pulled for such transgressions. I'll get this motor up to aircraft standards this summer.
When I experienced a similar issue on my 37.5 with a 3JH2E I found the exhaust elbow almost totally clogged. I replaced and issue gone. I now keep a spare exhaust elbow and the piece that is utilized (all threaded coupling) to connect the elbow to the exhaust manifold.
Well I just ran from hilton head back down to ft pierce running 8-10 hours a day for a week at 2,400-2,500 and no over heating issues.
The last thing I replaced was the raw water pump, which I think finally fixed it. I suspect there was no smoking gun, just a bunch of old parts that were due.
I replaced the entire pump including impeller and cover plate.