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Author Topic:   Mercury 150-HP Cooling Problem

jrnyman posted 09-06-2009 09:09 AM ET (US)
Hi, I have a [1989] Mercury 150 XR4. I haven't run [the engine] in the water yet, only with a hose adaptor. When I run [the engine] with the hose adaptor, [the cooling system aspirator] starts to blow warm air than spits a decent amount of water out of the [cooling system aspirator] at first, than as [the engine] heats up [the output of the aspirator] starts to turn to steam and eventually becomes all steam. If I shut [the engine] off and restart [the engine] right after, [the output from the cooling system aspirator] does the same thing. I [measured the] temperature of the head at [185-degrees-F]. I put new thermostats in [the engine] and checked the water pump impeller, which I replaced last year and only used the boat twice. [The water pump impeller] seemed to be ok. I have the warning beeper disconnected and I mix the oil manually. So [I am] wondering if [the engine] could be overheating. I [read] something about the cylinder head gasket letting the exaust get into the water jacket and overheating the engine.This [problem] is driving me crazy, I hope someone can help me out. Thanks so much.
jimh posted 09-06-2009 01:10 PM ET (US)
I do not recommend operating the engine with the warning buzzer or aural alert disconnected.
Try running the engine with the gear case submerged in a barrel of water. This will give you a better idea of how the cooling system is working. Running on a hose adaptor might be causing a problem.
Typically on a Mercury outboard there should be a flow of water from the cooling system aspirator once the engine jacket has filled with water. This often takes a minute or so to occur. If you never get any water from the aspirator, there must be something awry in the cooling system. Either the water pump cannot produce enough flow and pressure to raise the water to the power head, or you have a leak somewhere and the water is being diverted.
If the gear case was improperly assembled to the midsection, the water pump output may not be properly connected to the rest of the cooling system.

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Author	Topic: Mercury 150-HP Cooling Problem
jrnyman	posted 09-06-2009 09:09 AM ET (US) Hi, I have a [1989] Mercury 150 XR4. I haven't run [the engine] in the water yet, only with a hose adaptor. When I run [the engine] with the hose adaptor, [the cooling system aspirator] starts to blow warm air than spits a decent amount of water out of the [cooling system aspirator] at first, than as [the engine] heats up [the output of the aspirator] starts to turn to steam and eventually becomes all steam. If I shut [the engine] off and restart [the engine] right after, [the output from the cooling system aspirator] does the same thing. I [measured the] temperature of the head at [185-degrees-F]. I put new thermostats in [the engine] and checked the water pump impeller, which I replaced last year and only used the boat twice. [The water pump impeller] seemed to be ok. I have the warning beeper disconnected and I mix the oil manually. So [I am] wondering if [the engine] could be overheating. I [read] something about the cylinder head gasket letting the exaust get into the water jacket and overheating the engine.This [problem] is driving me crazy, I hope someone can help me out. Thanks so much.
jimh	posted 09-06-2009 01:10 PM ET (US) I do not recommend operating the engine with the warning buzzer or aural alert disconnected. Try running the engine with the gear case submerged in a barrel of water. This will give you a better idea of how the cooling system is working. Running on a hose adaptor might be causing a problem. Typically on a Mercury outboard there should be a flow of water from the cooling system aspirator once the engine jacket has filled with water. This often takes a minute or so to occur. If you never get any water from the aspirator, there must be something awry in the cooling system. Either the water pump cannot produce enough flow and pressure to raise the water to the power head, or you have a leak somewhere and the water is being diverted. If the gear case was improperly assembled to the midsection, the water pump output may not be properly connected to the rest of the cooling system.