Engine Overheating

[raro3]

I used my new Frances 26 for the first time this week; I was a bit alarmed at how slow she was under power, and then at the worse possible time the engine alarm went off. She has a Beta 14 (with a new water pump) and there seemed to be plenty of water coming out the back. When I returned to my mooring I took a look underneath, and the prop was pretty badly fouled (she hadn't been used for a few months) and I guess that accounts for the lousy performance. However, would a badly fouled prop really cause overheating of the engine, or should I plan to dismantle the heat exchanger? Any advice would be appreciated.
Thanks, Phil

 

[earlybird]

My first port of call would definitely be to clean the h/exchanger. I don't think that you can blame the fouled prop.

 

[LittleSister]

No, I doubt fouled propellor would cause overheating. The engine should be able to run at max revs (3,600rpm) and full power without overheating. Even if you were at max revs I imagine the engine would not be running at full power with a heavily fouled prop.

Well, cleaning out the heat exchanger is fairly simple, and will eliminate one thing, but I doubt that's the problem as it is the seawater side (inside the tubes) that is more likely to be clogged that the outside.

1)Are you sure there was enough water coming through?
2)Is the freshwater side of the heat exchanger full?
3)Checked the thermostat?

Re 2 -If inadequate seawater throughput:
Heat exchanger blocked
Intake logged by plastic bag/seaweed/ceatures?
Impellor or pump plate or back worn?
I assume the Beta 14 was a re-engine, not the original motor. Is the seawater inlet skin fitting and seacock big enough? (3/4 inch from memory.)

 

[ex-Gladys]

Were you getting black smoke? When I bought Gladys she was badly fouled and had a "cosy" of tube worms on the prop. The 47hp Lancing Ford, got us up to 1.7 knots flat out with loads of black smoke, and if you over fuel like that the engine will overheat, just from the thermal generation of burning all that fuel with less air being pulled in because of rev reduction...

 

[Tranona]

Overloading could be causing the overheating, and probably with a clean prop it will bring the temperature down enough to stop the alarm. The engine you have is more than enough for the boat so you should not have to run it over about 2500 for cruising speed. As suggested the heat exchanger could need cleaning as they do tend to to get bunged up. Also check the anode in the HE.

 

[sniffyjenkins]

Impellor wearing/breakage or blockage in intake are always first on my list of things to check in this situation. Can't imagine a fouled prop would be the culprit.

 

[Tranona]

Impellor wearing/breakage or blockage in intake are always first on my list of things to check in this situation. Can't imagine a fouled prop would be the culprit.

He says plenty of water coming out of the exhaust and it has a new water pump - so rules out those causes. A fouled prop that reduces speed so much can indeed cause overheating by overloading the engine, particularly if the heat exchanger is partially blocked.

Hence the advice to clean the HE first.

 

[peteK]

If the prop is fouled the hull will be as well which will account for slow speed.

 

[Topcat47]

The Beta is indirectly cooled. The water coming out will be from the SW side. Blockage in the FW side will have the same effect. As it's "New to Raro3 this could be something as simple as a kink in a rubber hose to the engine, or a collapsed hose due to internal failure. A leak in the FW side, a "failed shut" thermostat or a failing Head gasket are also possibilities. Is there enough water in the header tank? Also will be two water pumps, one for the SW and one for the FW circuit.