Gas engine overheating

[labrador]

Ok this weekend spent replacing stb fuel pump and fresh water pump that my wife left on with a leak in the system. found the leak too late so replaced the pump.Diver cleaned the bottom, running gear and intakes. Cleaned the strainers and have good water flow from the seacock. Over 3200 she will creep up to over 195 on the std engine only. Risers are only 3 yrs old and for the past year have been in brackish fresh water. Anyone have a suggestion for the next step? Really hot in the engine room this time of year, must have lost 20 pounds down there this weekend!!!!

 

[garyd]

This can be tricky. Ive had some pretty interesting things over the years make engines run hot.

I bought a boat that had been sitting in the water. As it would naturally bob up and down it formed a ring of salt/stuff. Well over the years this ring changed the diameter of the pipe after the seacock and after the strainer from 2" to about 1". It ran great until you got to fast cruise then it would overheat. I got very lucky and found it quick. knocked out the ring no more overheat.

In order to eliminate the water pickup system I would switch the raw water intake system from port to starboard and stb to port. If the problem then switches over ya know where to look.... If not then it's in the engine.

Had another boat that the same basic thing happen but inside the engine water routing system. It was a boat that was traded in "I believe cause the po couldn't find the problem". anyway the mech. finally found it a partially pluggged large water line. knocked out the buildup problem went away.

garyd

 

[brian4190]

the first two things i would look at are the thermostat and the raw water impeller(asumming you already checked your coolant level). first remove the thermostat and see if that corrects the problem. if it does replace it. if not change out the impeller. this should be done as peventative maint every so often anyways.if still a problem check the exhaust while you are running hard to make sure you have the same amount of water comming out of each side.if you have less on the side that is overheating you may have a raw water blockage. if you do have even water flow you may have to have your heat exchanger checked.

 

[garyd]

Brian is correct. I would of thought you would of started there and those items were not the problem.

If you havn't checked them start there and keep going. One thing for sure you will find it.

garyd

 

[labrador]

Thanks guys, I checked coolant 1st and will change impeller. Haven't had experence with the thermostat however will RTFM (read the friggin manual) to see what temp and where the d#$@^ thing is. Guess you can see I'm no mechanic!!!

 

[krush]

also, if you have any tranny coolers, oil coolers, etc, make sure to backflush them as they can catch crap if you do not have sea strainers.

 

[Maynard Rupp]

The most likely problem is the sea water pump. If you have EVER lost any of the rubber impellers, they could easily migrate downstream and restrict the flow. I don't beleive you have a thermostat problem as you say the temp creeps up. If your thermostat is stuck closed, the temp will continue to rise quickly and won't stop until the engine fails. If the thermostat is stuck open, the engine won't get much beyond 140 degrees. Have you changed your engine pencil zincs lately?? Do that. Remove the sea water pump, (a real bitch on the starboard engine). If any of the impeller lobes are cracked or missing, replace the impeller. You will need a gear clamp, some dish soap, and a bunch of bad words to get that stupid thing back in there. If you don't have it perfectly lined up with the key, the key will roll out. You will know it has done that because the impeller will stop going in with about 1/8" remaining. If you have lost impeller lobes, you must find all of them. Remove hoses and do whatever it takes to locate and remove them.

 

[Ross]

Need to look at the impeller housing also.If grooved a new impeller will not be the final fix. have seen pump covers and cams worn to the point that it still runs hot.If pump is more then five years old i would replace the whole unit.

 

[smoothmove]

Wouldn't it be a valid test to measure the water output at the exhaust? I've done it with a bucket and a stopwatch a couple of times and have a baseline volume vs rpm, but perhaps labrador would see a difference from one engine to another. Just a thought.
Eric

 

[67hat34c]

remove the risers and elbows and acid wash them. remove the heat exchanger and acid wash it. remove oil cooler and acid wash. drain the engine and fill with water and add the engine flush acid and run it for about 5hrs, drain and rinse then re fillwith 50-50 coolant/distiled water solution.

may as well do both engines,