overheating 40hp....Impeller or something else?

[imported_bboat]

Hi everyone....I've got a 1985 Evinrude 40hp that is experiencing an overheating problem. When I start the engine up, it takes about 10 seconds for the water to start "peeing". Then after another 2-3 minute of running at mid-throttle, the overheating alarm goes off. During this time, the temperature of the water leaving the engine fluctuates between cool and very hot to the touch...

Is this definitely the impeller? Can I get away with just replacing the impeller, or do I absolutely have to buy new gaskets,etc (the engine and boat are both in rough shape, so I want to spend as little money as I can)...thanks for any help!

 

[fireman57]

Re: overheating 40hp....Impeller or something else?

I would replace the impleller if it is more than three years old anyway. While you have the lower unit off hook up a 1/2" garden hose to the copper tube with a radiator clamp and flush the system. you probably have stuff gathered up behind your thermostat or a bad stat. You will probably have to remove the tstat to get a good flush. You can check the tstat by dropping it in hot water and see if it opens but I would just replace it. The cost is nominal. Welcome to iboats!

 

[imported_bboat]

Re: overheating 40hp....Impeller or something else?

thanks for the help man, I really appreciate it...I'll definitely give that a shot.

With the t-stat, can I remove that from the engine all together (like I've seen people do to cars down here in Florida where it's always hot) to ensure that I'm getting maximum flow, or is that just a bad/unnecessary idea?

 

[fireman57]

Re: overheating 40hp....Impeller or something else?

You can remove it completely but I wouldn't run very long without it. It not only keeps the water at the proper temperature but it also keep the pressure constant so that all cooling passages are filled. Ensures that both cylinders are at the same temperature. While you have the stat out you can put a 3/8" nipple on it and it will fit in the passages where the stat sits to further flush out the powerhead. You might even have some stuff in your exhaust cover that partially blocks the flow to your telltale.

 

[imported_bboat]

Re: overheating 40hp....Impeller or something else?

ok thanks I'll just replace the stat then with a new one...also, is there any homemade solution that people use to flush out the cooling system in their engine?..obviously it'd need to be strong enough to eat through corrosion and all that, but gentle enough as to not tear anything up....

 

[mikesea]

Re: overheating 40hp....Impeller or something else?

Some guys "gut"the thermo.cut the two strait pieces that above where they join the round part of the housing ,where the plunger kinda rides,cut the stainless rod too.Now you will have a top with 2 legs ,put your rubber around the top it it fell off.Not to critical though. This will allow plenty of flow.but give a hit of restriction so it dont get too cold in cooler months. I worked a couple places in the Keys and thats what they do here.Not to be done with the looper and newer that need temp.control

 

[fireman57]

Re: overheating 40hp....Impeller or something else?

As far as the flush there are products out there but at this point can'r remember the name of any. If this is a salt water engine I know that a lot of people use a product called saltaway. If you have a bunch of hard stuff in your passages you will want to use a product like that. Do a search on this with the search button at the bottom of the thread.