new to th sight 4.3 mercruiser overheating

[MCFAM]

I just purchased my 1st boat it is a bay liner 195 with a 4.3 mercruiser I/o. It has a fresh water system that overheats at idle and runs around 200 at full throttle. The impeller was replaced last season and I flushed the system with a hose and replaced the thermostat, but it continues to overheat, what else can I check? When it gets hot and I shut it down to cool the motor acts like it is vapor locked and won't turn over for a while. I just lost the starter my last trip trying to get it to unlock, does anybody have any suggestions about that?

 

[Fun Times]

acts like it is vapor locked and won't turn over for a while. I just lost the starter my last trip trying to get it to unlock.

Hi there, welcome to iboats! When you say locked up, was the engine not cranking/spinning over? You may want to pull your spark plugs for a full inspection as you may have/be getting water into the cylinders. If so, the first thing to suspect would be defective exhaust manifolds.

How's the water flow out the exhaust ports on the transom assembly?

 

[Bondo]

I just purchased my 1st boat it is a bay liner 195 with a 4.3 mercruiser I/o. It has a fresh water system that overheats at idle and runs around 200 at full throttle. The impeller was replaced last season and I flushed the system with a hose and replaced the thermostat, but it continues to overheat, what else can I check? When it gets hot and I shut it down to cool the motor acts like it is vapor locked and won't turn over for a while. I just lost the starter my last trip trying to get it to unlock, does anybody have any suggestions about that?

Ayuh,.... Welcome Aboard,... Change the Impeller, 'n possibly it's housin' this time,....
If that don't fix the overheat, pull the risers to see if they're plugged up,...

 

[Bt Doctur]

DO not to operate it above 175 deg. Do you mean you have a heat exchanger and the engine uses regular anti-freeze?

 

[MCFAM]

No I have the system that draws from the lake and goes out the exhaust, I am sorry I don't know all the technical terms yet. The engine froze up and was just clicking like the batter was dead, but I checked it and it was fine, and after trying to start it for awhile the starting went out trying to turn the motor over. When I hook up the earmuffs I have plenty of water through the exhaust. What is the best way to flush out the system and make sure I don't have any clogs anywhere? I did check the oil for water and their isn't any so I don't think it got hot enough to take out the head gasket. I also found out the previous owner had disabled the overheating alarm so that is why I didn't get a warning.

 

[Bt Doctur]

replace the therm with a 140 deg one. replace the impeller with the full kit including the water pump base. Hooked up the the muffs you should not have water exiting the motor when its off.
install the muffs , turn on water and look to see how much "splash" there is leaving the muffs
start the motor , immediately 95% should disappear, if no difference in the splash ,the impeller is bad

 

[MCFAM]

Thanks I will try that. When I put the new thermostat in it is real rusty looking inside, is there a good way to flush all the hoses and whole system with some type of cleaner?