Running Full Throttle/Overheating

[willisballs]

With an older model boat 18' and 1976 Envinrude 135hp....Running the boat at higher speeds for about 8-20 minutes seems to cause the engine to overheat....does this have to do with thermocouples, thermostat, or just running it too high.... ALso, (stupid question) but your not supposed to run at full throttle ever, are you?....Last question...if the motor where to overheat,and the alarm is not working and the temp gauge, does this model have an automatic cut-off switch before it reaches a "damage zone" <br />inside the engine?....THanks for your help,,,,

 

[reeldutch]

Re: Running Full Throttle/Overheating

you can run at wot but dont do it for anny long time.<br />may be your waterpump needs to be replaced.<br />i dont think it builds the pressure needed at higher rpm's.the impeller might be weak.<br />i would do that first.<br />if that doesnt do it than i would check out the tstats and waterflow restrictors<br /><br />i am not a mechanic just a doe it yourselfer wrench<br />reeldutch

 

[rodbolt]

Re: Running Full Throttle/Overheating

hello<br /> do a tune up on the cooling system. remove the heads and have a look at the deflectors. that motor if propped correctly and the cooling and lubricating system working as designed can hold 5K all day long<br /> good luck and keep posting

 

[DJ]

Re: Running Full Throttle/Overheating

Ditto rodbolt.<br /><br />No, it does not have a "failsafe". It will destroy itself.

 

[rodbolt]

Re: Running Full Throttle/Overheating

hello<br /> oh yea<br /> dont tell me the auto shut off story <br />I get 5-10 of those each season <br /> it does not have an auto off. usually the auto off means the pistons swelled so much they stuck in the bore and wiped themselves out.

 

[DMR Mechanic]

Re: Running Full Throttle/Overheating

I would recommend that the impeller be replaced every year. The blades on the impeller will get a set in them after sitting for a few months and not work as well. If the impeller is old, it most likely is not so flexable anymore. You should check the therm-o-stats every year too. Threm's can get pluged up from stuff in the water.<br />This kind of maintenance is a lot cheeper than a new powerhead. Happy Boating

 

[willisballs]

Re: Running Full Throttle/Overheating

Lol... thanks guys, thats what I was looking for, we were going to try the impeller first... and reeldutch, or whoever, when you say that "it might not be building enough pressure", are you referring to (generally, all or most engines running at higher speeds dont build enough pressure), or that (it sounds like my engine is not building enough pressure at higher speeds?)... THanks again, your info is priceless..

 

[willisballs]

Re: Running Full Throttle/Overheating

oh yea.... and the water coming out of the two holes in the back of engine under the hood... is that part of cooling system?...at low speeds it puts out adequate water, but at higher speeds(above plain) the water output is reduced to almost none...so are all engines supposed to put out water back there, ((note..the "****-line"(water coming out of the corner/side of the engine is steady and seems fine...)) and could this be in part fault of the impeller, gaskets/seals...and if so, would this be a condition that may cause overheating?<br />THanks again guys.....i really appreciate everything...

 

[willisballs]

Re: Running Full Throttle/Overheating

Any tips for when replacing the impeller?.......

 

[Dhadley]

Re: Running Full Throttle/Overheating

The number one tip on replacing the impeller -- dont.<br /><br />Change the complete kit.

 

[reeldutch]

Re: Running Full Throttle/Overheating

very likely your impeller of your waterpump is set. the blades of the impeller do not have the strenght to pump enough water under higher pressure.<br />never run the motor without water or it will burn your rubber impeller.<br />yes replace the whole waterpump.<br />i replace my waterpump every other year.<br /><br />good luck reeldutch