V8 overheating problem ( 5.7 mercruiser)

[bassarama]

Hey gang

Yeah yeah I know.... it's an I/O ::)

Anyways, I took this boat for a test drive and 1/4 of a mile odwn to the river the darn motor overheated...

The owner( geez THAT never happened before) :D

Me: Riiiiiight!!! uuuuhh uh :o.


At any rate, The guy says the problem is a raw water pump.

Optimistically, I say it's blown head gasket/s. Now in case I'm right do you think that the overheating may have cause severe damage to the heads/ block ?

Thanks for any advise.


Joe

[frayed_knot]

How hot did it get? I would suspect the raw water pump as well, but if it got really hot, then yeah, the heads could be trash. There is also the water pump on the front of the engine to consider as well. What makes you think head gasket (just curious, not argumentative)?

[spareparts]

a raw water pump is probably what is wrong, they are notorious for going out. a simple compresion check will tell you if the head gaskets are shot( it may not indicate if they are cracked however). An easy way to check the water pump is to pull the hose off the thermostat housing that comes from the power steering cooler, look in there to see if you see any pieces of impeller, hook a flusher up and crank the engine up with the hose off, you should get a nice steady stream of water, about what you would get if you cut the end off a garden hose and turned the spigot on. Another thing to check is the exhaust risers and manifolds, not a real good way to check them other than looking at the condition, and questioning the age, if the boat is in salt and the engine has been flushed regularly, expect 5 to 7 seasons if you're lucky, if the engine hasn't been flushed regularly, figure 3 to 4 seasons at best. The manifolds will stop up, not allowing the hot water to exit the engine, you may notice a burnt rubber smell associated with either of these problems, its the exhaust hose burning up due to lask of water mixing with it. A bad circulation pump can cause the engine to heat but usually the bearing will go out, allowing the main pulley to wobble noticably( i have seen the circulation pump impeller rust off inside the block,its rare but can happen). *Stuck thermostats can cause overheating as well. If the alarm went off, they are usually set at 215( what good is an alarm that tells you its too hot too late?), most new cars run that temp everyday, so you may be ok on the engine

Check the water pump first, then inquire to the age of the manifolds( they can be expensive)

[macojoe]

Did I say I hate I/O yet??

On mine first the Out drive pump went, then the water pump on the engine, then the Manifold let go. O yea then the exhaust bellows

If fresh water cooled the the exchange boxes might have rotted threw mixing salt with antifreeze.

O yea the list goes on!! and nothing is cheap either!!

[spareparts]

easy now, those things have supported me for the last 22 years ;)

[macojoe]

Exactly what I mean!!

[bassarama]

Thanks guys

I consulted a couple of marine mechanics and they told me it could be the head gaskets.

The motor is 9 years old so I assume the risers and manifolds are shot, again my worst fear is the induced heat on the motor causing internal damage like on the heads etc. etc.

I really don't know how hot it got but I saw the temp. Gauge maxed out.

Funny thing was, even overheating this frigging motor revved up quite well, the motor responded to the throttle when trailing on the boat.

Thanks

Originally Posted by macojoe

Did I say I hate I/O yet??

!!

i have to say this agian

whats wrong with i/os

i think that a muscle boat cant be a true muscle boat enless it an i/o

[charlie_the_tuna]

does the mercruiser even have a raw water pump?

no my has a fresh water holding tank i have to fill if it get low.