overheating

[skcc]

I have a 1983 0mc 230 hp and cannot figure out why it is overheating at about 3000rpm. once she gets hot I slow down to a troll speed she cools down very fast and then i can get on plane again for a minute or two then gets hot again. Changed the impeller whats next?I have just realized there is no thermostat so have ordered one and im changing the water pump would not having the thermostat cause the water to go right out the manifolds and not through the engine? are there common areas to chech for water blockages?

 

[MainstreetUSA1]

Re: overheating

If you have a raw water cooled setup.<br /><br />It has been discussed on previous posts that running without a T-Stat may cause the engine to operate at a higher temperature. This may occur because cooling water may circulate at a such a pace through the water jacket that heat generated by the running engine does not have enough time to transfer from the block into the cooling water.<br /><br />What did the old impeller and housing look like? Were there rubber vanes missing? If there were, you should make an effort to recover them from the cooling system by back-flushing and checking hoses and fittings for blockages. Also, risers and manifolds can be problem areas for rust to constrict coolant passages causing a water flow issue. You can search previous posts for information on the replacement intervals for risers and manifolds for given enviroments (salt/fresh water) and usage (hours per boating) season.

 

[deputydawg]

Re: overheating

Welcome aboard both of you. <br /><br />Running without a Tstat will definately run it a little hotter because the water is not in the engine block long enough to absorb the heat. In a car they will run hotter because the water does not stay in the radiator long enough to cool down.<br /><br />Have to wonder why the T stat was removed to begin with. Your on the right track with the water pumps and the stat. Also make sure that it is in fact getting hot. The guage may be wrong.

 

[vicsponjr]

Re: overheating

I have been experiencing the same problem. Someone suggested checking the impeller housing for a good seal. Once on plane the pump may be sucking air. Haven't checked mine yet, but when I installed the impeller I fed water thru before replacing the cover and there was some water seeping out of cover. Hoping that is my problem.