High Temperature 4 hp Head

[undervfronly]

I have a 1988 4 HP Evinrude. The motor feels very hot at the head even though water appears to be flowing from water inlet to exhaust port. It is too hot to touch after a few minutes of running. Does anyone know how hot the head should get if water is flowing through?

 

[sutor623]

Re: High Temperature 4 hp Head

Man I'm not sure when thy switched over, but I had the same issue with my 1970 4hp. Both of them actually. Is it a salt water motor? The salt blocked my passages up. http://forums.iboats.com/showthread.php?t=532341&highlight=johnson+4r70e

 

[undervfronly]

Re: High Temperature 4 hp Head

It has been used in both fresh and salt but it has been fllushed after every use.

 

[sutor623]

Re: High Temperature 4 hp Head

Mine seems to get pretty hot to the touch, even after I did a full gasket and waterpump job, and cleaned out all of the ports. Make sure to run a 24:1 mix (about 6oz per gallon) instead of the 50:1(48:1) that was recommended by the factory. That helped to keep my motor a little cooler also. Check compression and see if you have had any overheat damage in the past.

 

[sutor623]

Re: High Temperature 4 hp Head

To iterate on the oil mix, since these motors only have one crank bearing, most of the big boys on here agree that a richer oil mixture is required to run this motor safely.

 

[nwcove]

Re: High Temperature 4 hp Head

that motor should be happy at 50:1.....but a little extra oil is well worth it. when you say the head is hot....are you touching the head, around the plug area? if so...that will be quite hot as its not water cooled. but if you are touching behind the head on the opposite side as the exhaust plate, you should be able to keep a finger on it for a few seconds and not loose any skin.

 

[hidef]

Re: High Temperature 4 hp Head

The 1988 4 horse uses all bearings there are no bushings to worry about so 50:1 is the correct oil mix for your engine.

The side of the cylinder will be around 163 degrees or maybe a little hotter use an infrared thermometer or a 163 degree thermomelt stick to check it after running the engine at or above 3000 RPM for 5 minutes. The head will be hotter then the side of the cylinder. If the cylinder is above 163 change the waterpump.

 

[James R]

Re: High Temperature 4 hp Head

Just finished going over a 1979 model , carb, lower unit etc and yes the head does feel a little warm. The exhaust plate is cool. Running 50:1.
I dont think the warm head is an issue. Motor runs very well.

 

[SolingSailor]

Re: High Temperature 4 hp Head

I believe the manual states the temp should be between 100 and 163 degrees fahrenheit. My 4 hp measures 130 on an infrared thermometer.

 

[sutor623]

Re: High Temperature 4 hp Head

I believe the manual states the temp should be between 100 and 163 degrees fahrenheit. My 4 hp measures 130 on an infrared thermometer.

So I'd get 163degree thermomelt stick and if it melts there is an issue.

 

[undervfronly]

Re: High Temperature 4 hp Head

So I'd get 163degree thermomelt stick and if it melts there is an issue.

Pulled the lower unit the pump is shot. I was using a hose with a "modified" flush and it must have been pushing water directly into the lower exhaust port simulating water pumping. With water applied directly to the lower supply tube the exhaust cover runs only warm as expected. Thanks for the input. As far as the mix goes I have run 50:1 even though for some reason the cowling states 100:1 mix. Plugs do tend to fowl more often than expected - which is a pain with the cover being so tightly screwed on.

 

[Chinewalker]

Re: High Temperature 4 hp Head

If the plugs are fouling, something else is amiss. Fuel system issue, weak spark, low compression, etc., but not because of oil mix.

In the late 1980s Johnson and Evinrude thought it would be a good idea to lean out the mix to 100:1. Motors coming in for warranty work with bad cranks, busted rods, & stuck pistons taught them otherwise and they rescinded the 100:1 recommendation back to 50:1. Dealers were supposed to remove the 100:1 stickers...