Can the wrong prop overheat motor???

[Joe Fisherman]

I have a 60 hp johnson 1989 that I have replaced impeller/water pump ,thermostats,checked and cleaned water jacket and warning buzzer comes on at full throttle. The last time I took the boat out I noticed that just under full throttle that it would not run hot.I bought this motor used and I am wondering if it has the wrong prop on it can that run your motor hot which would explain why it only runs hot at full throttle????????????

 

[roscoe]

Re: Can the wrong prop overheat motor???

I could , under the right circumstances. What are your rpm's at wide open throttle?

 

[Joe Fisherman]

Re: Can the wrong prop overheat motor???

My rpms are about 5000 The prop on the boat is a michigan 13 1/4x 17 the boat is a 17ft cobia bowrider.

 

[roscoe]

Re: Can the wrong prop overheat motor???

Well, you are not lugging your engine, so I doubt the prop is contributing to the overheat situation.

 

[Specks n Reds]

Re: Can the wrong prop overheat motor???

 

[SCO]

Re: Can the wrong prop overheat motor???

I'm having the same problem. Do you run it in salt water?<br />Might also be lean running engine...that will melt a piston so maybe will overheat also. Cant hurt to put in carb kits and check that timing is to spec.<br /><br />I have a question to throw into the mix that might help us both: Can you catch the water from the telltale over a timed interval at wot into a a jug to determine if you are getting the proper cooling water flowrate through the engine?

 

[roscoe]

Re: Can the wrong prop overheat motor???

Is your engine a multi carb model? Maybe you have one carb running lean at WOT. ?????<br /><br />Or, maybe your temp sensor is bad. Should probably determine if it is actually overheating by using a temp stick or a temp sensor gun.

 

[clanton]

Re: Can the wrong prop overheat motor???

The block was changed on this engine, and I do not know what year the change was made, but if this is a later block engine, it needs a temp sensor with a 7 inch pigtail, tan/blue stripe wire. I will check on the change.

 

[Joe Fisherman]

Re: Can the wrong prop overheat motor???

Thank you SCO and Roscoe my carbs were rebuilt when we put the motor on and we adjusted the carbs on the hose so mabye it is running lean cause my plugs are a burnt orange color.At full throttle can running lean really cause overheating?? My buzzer will come on for about a sec till i idle down then its fine till I take it full throttle again then buzzer again!!!!

 

[Joe Fisherman]

Re: Can the wrong prop overheat motor???

Bump!!!

 

[Solittle]

Re: Can the wrong prop overheat motor???

Any adjustment to carbs must be made with the motor in the water & not on muffs. The motor needs the back pressure from being in the water.

 

[ob]

Re: Can the wrong prop overheat motor???

Joe Fisherman,The answer to your question"can running lean at Full throttle cause the engine to overheat?"is yes.Two strokes will gain in rpms and power at the upper throttle range if leaned out.Problem is lack of lubrication that leads to eventual meltdown if not addressed.As you mentioned in your previous post ,the sparkplug condition is an excellent barometer in detecting a lean running cylinder.<br /><br />Outboard propeller selection for a given hp to boat weight/lenghth is probably the most important item that will insure long life and trouble free engine operation.<br /> I think you are propped too steep with a 17" pitch pushing that 17 1/2 foot rig.I would reduce at least back to a 15" pitch.Rpms at wot for that engine should be 5500-6000.Nearer 6000 would be better.This also contributes to higher engine temps due to lugging.