Running Hot... 89 4.3 cobra omc

[BigNick617]

Okay here goes... I have an 89 four winns 4.3 cobra... dewinterized the boat dropped it in the water took off... noticed that when I came to an idle the boat would slowly creep up towards 230 degrees... plane out and it cooled right down... okay... took it home inspected the impeller and it was fine just replaced last fall... housing looked okay and so did the gasket... hooked up the muffs and started frunning the boat at idle... slowly started geting hot... removed hose that goes into the thermostat housing from lower unit and was geting no flow... took off hose and impeller housing and backflushed the system... could push water up to the block and could push water out of the lower unit... hooked everything back up and put the muffs back on started the boat and could not get it to run over 170... cool right? took it to the lake... dropped it in... and before I could get out of the cove it was pegged... no flow coming from the lower unit... I am at a complete loss... someone please help... my next step is to replace the impeller housing gasket, housing, impeller, and water pump... already replaced the thermostat i forgot to mention... once again any help would be greatly appreciated...

 

[HT32BSX115]

Re: Running Hot... 89 4.3 cobra omc

Howdy,


You probably have a blockage between the raw water pump and the t-stat housing Do you have a power steering or an engine oil cooler?

It's possible that you have impeller remnants or other debris blocking the flow of water from the pump. It could also be debris in the t-stat housing itself.

ALL the water pumped from the raw water pump is pumped into the housing, and onto the manifolds/risers and eventually overboard.

If there ANY sort of blockage along the way (including in the manifolds/risers) preventing the water from flowing, it will cause overheats.

If your "new" impeller was ran dry for even 30 sec, it could be damaged enough to fail.


Regards,


Rick


Oh..........and Welcome to iBoats!!

 

[BigNick617]

Re: Running Hot... 89 4.3 cobra omc

I have already taken the pwer steering cooler of and inspected it... it was free and clear... I understand that blockage anywhere can cause the overheating issue... however my concern is that the problem seems to be intermitent... and if I cannot get water to the block then blockage in the risers or manifold doesn't seem a relevent issue at this point... not to say that they aren't blocked... Like I said before I'm going to go ahead and replace the impeller kit housing and all... throw a water pump onif that doesn't work??

 

[HT32BSX115]

Re: Running Hot... 89 4.3 cobra omc

I have already taken the pwer steering cooler of and inspected it... it was free and clear... I understand that blockage anywhere can cause the overheating issue... however my concern is that the problem seems to be intermitent... and if I cannot get water to the block then blockage in the risers or manifold doesn't seem a relevent issue at this point... not to say that they aren't blocked... Like I said before I'm going to go ahead and replace the impeller kit housing and all... throw a water pump onif that doesn't work??

You also have a hose and fittings etc, that goes from the drive to the T-stat housing. #18, #37, #68 below.

If there's impeller fragments or other debris in there it can also cause a restriction.

90% of all overheating problems are related to the raw water pump and associated plumbing.........