1994 4.3tks V6 mercruiser overheat problems

[fort4short]

I just got my boat from winter storage this last wekend. I put in a new thermostat, I hooked up the Water muffs to the lower unit and started the motor. I monitored the temp gauge and saw no movemnet, I checked the engine compartment for leaks and saw none, I noticed that the exhaust manifolds were extrimly hot, I shut down motor, removed riser drain plugs and had steam coming out. I pulled the engine drain plugs and cool water ran out, I removed the thermostat housing cover and saw no water on top of thermostat. I replaced the cover, and started the wateron the muffs again and had water going through all drain plugs. reinstalled plugs and started motor up again same problem,.

can this be a bad water pump or a bad recirculation pump? any Ideas. should I take it to the boat ramp and start the motor up again and see what happens, I do not want ot damage the motor..

 

[RogersJetboat454]

Re: 1994 4.3tks V6 mercruiser overheat problems

can this be a bad water pump or a bad recirculation pump?

Yep,
I'm going to assume here you have an Alpha drive (but you know what they say about assuming)...
When was the last time you replaced the water pump impeller in the drive? Depending on your boating conditions, this is something that should be done every 1-3 years, favoring on the sooner side if you boat in salt water.

 

[fort4short]

Re: 1994 4.3tks V6 mercruiser overheat problems

I bought it used last year, I only had about 30 hours on it. it is the alpha 1, do you think I did any damage to the exhaust manafolds or the engine? should I take it to a boat ramp and restart it and see what happens or just replace it? also wouldn't the muffs and garden hose prevented the exhaust manifolds from getting hot?

 

[Don S]

Re: 1994 4.3tks V6 mercruiser overheat problems

At this point, it's hard to say. I notice in your title it says 1994 4.3tks V6 mercruiser. The TKS didn't come out until much later. Do you have any engine serial number from your engine? Do you have fresh water cooling? If so, do you have a belt driven raw water pump?

 

[RogersJetboat454]

Re: 1994 4.3tks V6 mercruiser overheat problems

I bought it used last year, I only had about 30 hours on it. it is the alpha 1, do you think I did any damage to the exhaust manafolds or the engine? should I take it to a boat ramp and restart it and see what happens or just replace it?

If you are unsure about the maintenance history of the impeller, best to start by replacing it. If you find that the impeller is missing vanes, you need to start pulling the cooling system apart to find the missing pieces, because generally when they do break free and get pushed into the cooling system, they will usually restrict water flow and cause further overheating issues even after the impeller has been replaced. Places to check would be the oil cooler, T-stat housing, smaller hoses, exhaust manifolds/risers, etc.

Hard to say if the overheat did any damage BTW. Usually the rubber hoses from the risers to the exhaust inlets, and the flapper valves are the first things to burn up. Might be worth checking those out.

 

[fort4short]

Re: 1994 4.3tks V6 mercruiser overheat problems

I do not have the serial number right off hand. the boat is a 1994 Bayliner. it is a open cooling system (water taken from the lake) not a closed system.

 

[fort4short]

Re: 1994 4.3tks V6 mercruiser overheat problems

in that case, I will wait to have some one check the water pump for me. I am sure a good machainc will know what to look for

thank you for your replys