Merc overheating…

[Lanny2005]

I have a 2004 Crownline 240EX, powered by a 5.7 350 Merc Bravo 3. It only has about 200 hours on it. It has not had routine maintenance, but I do check oil/gear Drive levels periodically. Water pump has been replaced once, otherwise no mechanical issues…until now. Took it out yesterday, had gone about 1/2 mile at 15-20mph, and a continuous alarm beep sounded, about the time my wife said stern seat was getting warm and something smelled like it was burning. Engine temperature was over 200*F, and oil pressure was about 14PSI. Dipstick was naturally covered with oil because engine was hot, gear lube reservoir was full. Made it to dock 200 yards at a time, keeping engine temp below 240* by allowing it to cool for 5 minutes at a run. I am no “shade tree mechanic,” but am mechanically inclined and can follow instructions. Before I borrow a trailer and haul it in for servicing, is their some simple troubleshooting I can do? I’m going to check the oil level with the engine cold, but what else should I look at/for? I assume since it has a water pump, the engine is completely water-cooled; no coolant level to check/top off.

 

[matt167]

This is where a little routine maint would have prevented an issue. Impeller has a 90% chance it quit pumping. Burning smell because the exhaust got HOT from lack of cooling

 

[Scott06]

Yeah you probably cooked the exhaust rubber.

May have hit a plastic bag or other debris blocking water flow. Would take the hose off the thermostat housing where water comes up from the seawater pump (belt driven) start the engine briefly and see if you get any water coming up to thermostat housing.

If not pull it. You probably want to check the exhaust rubber components like the hoses that connect to wye pipe and shutters.

also yes check the oil before starting if it got hot you can blow a head gasket and get water in oil

How long since th pump impeller was done? Use OEM merc parts for these vs cheapo aftermarket

 

[ROY WILLIAMS]

so you did not have a trailer ... well you have to go to the boat mechanic and the out drive impeller is a break down . boat mechanic also inspects the water engine cooling .
engine is around 240F ,, oil is 14 psi ...low pressure ,,,,,,,,,,,,,,,,typical around 40 psi ...normal..

the impeller is a CCP part ....

 

[Bondo]

so you did not have a trailer ... well you have to go to the boat mechanic and the out drive impeller is a break down . boat mechanic also inspects the water engine cooling .
engine is around 240F ,, oil is 14 psi ...low pressure ,,,,,,,,,,,,,,,,typical around 40 psi ...normal..

the impeller is a CCP part ....

Ayuh,..... He's got a Bravo, the impeller pump is mounted on the motor, not in the drive,.....

Lanny,.... Welcome Aboard,...... Start at the impeller pump, 'n go from there,.....
Hot exhaust, equals no water,.....
Ya probably burnt up some exhaust parts too, such as the shutters, 'n rubber couplers,....

 

[Scott Danforth]

do a compression check

running back like you did, you may have warped your heads

remember, rubber bits like an impeller do not care how little you use the boat. their calendar starts ticking away the moment the part is released from the mold.

Impellers are a change every few years type of thing regardless if you use the boat or not.

 

[Lanny2005]

Yeah you probably cooked the exhaust rubber.

May have hit a plastic bag or other debris blocking water flow. Would take the hose off the thermostat housing where water comes up from the seawater pump (belt driven) start the engine briefly and see if you get any water coming up to thermostat housing.

If not pull it. You probably want to check the exhaust rubber components like the hoses that connect to wye pipe and shutters.

also yes check the oil before starting if it got hot you can blow a head gasket and get water in oil

How long since th pump impeller was done? Use OEM merc parts for these vs cheapo aftermarket

Thank you! I need to invest in a trailer regardless. Who will buy it from me (at some point) without one lol.

Ayuh,..... He's got a Bravo, the impeller pump is mounted on the motor, not in the drive,.....

Lanny,.... Welcome Aboard,...... Start at the impeller pump, 'n go from there,.....
Hot exhaust, equals no water,.....
Ya probably burnt up some exhaust parts too, such as the shutters, 'n rubber couplers,....

thanks for pointing out impeller is mounted on the motor. He’s coming out to work on it as it sits in the lift!

 

[Scott06]

Thank you! I need to invest in a trailer regardless. Who will buy it from me (at some point) without one lol.

lots of people dont own or want a trailer. Marina puts it in the water in the spring, takes it out in the fall, winterized, and stores it.
if you are diy type then u need one.