Overheating engine... frustrated!

malexander · May 1, 2011

Re: Overheating engine..Frustrated!

Possibly an air bubble preventing the proper circulation. I had that issue with my M25.

Mad Dog 3 · May 1, 2011

Diesel engine should run the 180F(80C) degrees range

what is the temperature at idle.

did you check:

Cooling water flow sufficient (visual at the exhaust).
be sure the exhaust not clogged!

if all good, then restriction on fresh water side or scaling whithin the system itself should be looked at!

Bill Roosa · May 2, 2011

The heat exchanger may have scale on the raw water side. this is slow over the years kind of buildup. Each overheat boils the raw water in the exchanger and that makes a small additional deposit. The deposits do not conduct heat as well as the raw metal tubes so you get overheating at high power first.
Pull the end caps and run a bottle brush through the tubes.

Merlin Clark · May 2, 2011

I had a boat once with a Perkins engine and Hurth tranny that would do hull speed at 1,400 rpm and over heat if operated at over 1,800 rpm.
After much chasing of tails it turned out a previous owner had over-propped the boat. Key indicator was hull speed at low RPMs.

Jeff · May 2, 2011

My Yanmar 30GM30F used to overheat at high RPM's. Turned out to be a leaking gasket on the strainer basket.

BarryL · May 2, 2011

Hello,

How is the engine water pump (not the seawater pump)? Have you checked it? Any signs of coolant leaking out the weep hole? Can you squeeze a cooling hose leading to or from the water pump and feel coolant circulating? It might be time to change the pump.

Barry

petersea · May 3, 2011

pressure test the coolant cap or replace it may not be the problem but can't hurt to try it

RichH · May 3, 2011

Check the exhaust manifold for the devlopement of 'slab rust'.

Cast Iron when molded cools by 'stratifications' (like an onion) and when rust (red ferric rust) forms it penetrates between the stratifications and breaks some of the areas of stratification loose as LARGE 'flakes' or 'platelettes' of rust. These 'flakes' will sometimes partly or fully block the cooling water exit of the manifold, run at low rpm or shut down the engine and the 'plates' fall to the bottom of the manifold, there to stay until water turbulent conditions in the future 'stir them up'.
Such 'ferric' rust is rapidly formed by 'drying' an engine for long periods of time, and is the reason that navy and large commercial ships hardly ever shut down their engines !!!!!! In small boat engines the chief cause of plate-rust is emptying the cooling water from the engine/manifold for long term storage.

Remove the manifold from the engine, go inside the manifold with a long stiff wire and break up the large platelettes of rust, then do a pressure hold check of the manifold to insure that the rust has not developed a pin-hole between the hot gas side and the water side.

To prevent slab rust (red ferric rust) ... run the hell out of the engine at it max. operating temperature as often and constantly as possible ... as this will allow the formation of black ferrous rust which is 'protective'. When long term storing the engine, run hard and long to develop the black ferrous rust and then drain the engine/manifold and add appropriate antifreeze AND rust inhibitor .... keeps the protective 'black/blue' form of rust intact which 'protects' the engine and lessens the formation of 'slab rust'. If you simply drain the water for long term lay-up and leave the manifold 'dry' the black rust will transform to red rust and that is 'destructive' and forms 'slab rust'. Internal corrosion and 'slab-rust' is what 'kills' marine engines.

MitchM · May 9, 2011

"....My Westerbeke 13A engine overheats after about 20-30 minutes....gets up to 215-225 degrees. Temp comes back down if I let it idle for 10 min....

from this fact you observed that the temp gets up high enough to overheat after 20-30 minutes , i am assuming there is a loss of adequate cooling at the higher engine temps and rpms. the cooling capacity is related to both the amount of cold raw water being pumped thru the raw water pump, and the amount of engine heat that can be transferred to t he r aw water from the antifreeze circulating in t he closed heat-exchanger system. so i assume both t he r aw water pump and impeller, and the fresh water antifreeze pump are functional, and not losing fluid through their weep holes ? . once you've decided that the pumps are functioning as designed, look for why ehat is not properly being carried off by the cooling systems . a scaled up heat exhanger could certainly do this but i would more suspect a piece of raw water pump impeller that is clogging the ht ex tubes. rx is to pull the ht exc run a pipe cleaner or straw thru each hole and be sure no pieces of broken impeller are trapped in there. if your ht ex is clean then look a t possible loss of coolant as a reason why your engine overheats:

-- are you seeing any loss of antifreeze coolant externally ie leak of antifreeze into the bilge from rear ht ex gasket, thermostat gasket, etc ?measure your a/f level, then run your engine to hot and see if you have lost coolant. if you have, that could be the problem.

--are you having to top up the antifreeze more often than usual ??

-----if there is an antifreeze leak in the pressure system of overflow container-radiator--ht ex-- thermostat, you can find a pressure leak with a STANT tester. this is a pressure pump that allows you to pressurize the closed antifreeze system thru the radiator cap. you can pressurize the system without running the engine at all or to hot. you need to get a stant cap that fits the rad cap on your westerbeke.some autoparts store will r ent you 1, i bought one for 445 on the internet..

--- i used the stant to find a very peculiar leak of antifreeze caused by pinholes in my hose loops from the t stat block back into the hot water heater. the hot water heater hoses that carry engine residual heat run from the t stat block back through the hot water htr, to heat the hot water htr water by engine waste heat. both hoses at lower circumference had both abraded on the bulkhead , and both hoses had pinhole leaks that only got serious when the pressure in the system was high, ie after my engine was running at 2800 rpm for 10-15 minutes. the engine temp gauge would be fine then after 10-15 minutes the temp alarm would go off . i could not figure out why. this leak drove me crazy as we could not see any fluid , water or antifreeze, in the engine compartment ( well that was because the antifreeze was draining out on the other side of the bulkhead between engine compartment and water heater, where the hot water hoses came thru the bulkhead . that way the pinhole leaks could drain right into the bilge..unnoticed by me ) .

also check for weeping of antifreeze from the antifreeze (also called) fresh water pump. this pump won't be under pressure from the stant, you could try fixing a colored cloth under it and run the engine to see if a leaky freshwater pump is causing your problem. (dont get the test rag caught in the alt belt or any other moving part...)

if your fresh water antifreeze system checks out, move to t eh r aw water system": assume a good new impeller and good gasket on the raw water pump, and no weeping under the r aw water pump...

-if you have a leak in the raw watersystem, i'd take a colored rag-- like a red shop rag -- and hold it methodically at every joint where raw water could be escaping : (watch for the rag to turn color when wet by water, that is why red is good . ) start at the raw water seacock inlet, go to strainer gasket, bottom of raw water pump especially check at the weephole , up to hose clamps on all hoses into/ out of counterflow part of ht exchanger.

now i have run out of ideas, let us know what you find....

fair winds from the hard at erie PA

Overheating engine... frustrated!

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malexander

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