One head over heating

[bmstang]

I was just wondering if anybody could help i have 78 235hp evinrude just put in 2 new thermostats and one head is not cooling. The other 1 and the power head are cool to the touch this one you will burn your hand on. I took the thermostat back out and checked to make sure it was popping and it is. I started it up with the thermostat out and the valve out it is pumping water out the housing but it is burning hot does anybody know what the problem is or what i should check thanks.

 

[emdsapmgr]

Re: One head over heating

Pull the head cover off on the overheating side. (not the whole head.) Have a look inside and see if any crud is blocking the water passages. If you see blockages, you might as well remove the head and check for blockages around the cylinder liners. If you don't see any blockages in the head, pull the head anyway and inspect the three rubber water diverters in the water jackets. They can get out of place or fill with debris, also causing blockages and overheats.

 

[bmstang]

Re: One head over heating

I pulled the head cover and the cover side was filled with corrosion almost to the point where the cover was smooth on the back side. On the head side a little corrosion but nothing filled nothing really to speak about. I don't really want to pull the head unless i have to because i did it on the other side to do a head gasket and when i took the bolts out 4 of them actually stripped out the threads from the block and the heli coils do not want to torque down they just spin. Is the crud on the cover side enough to make it over heat.

 

[emdsapmgr]

Re: One head over heating

Is this a saltwater engine? Certainly, you can always clean the inside of the head cover and replace it, then run the engine and check the head temp frequently with a laser temp gun. If it still overheats, you will have to pull the head. What you see inside the head is likely also in the cylinder cooling passages of the powerhead. The concern inside the block is that the water is able to easily circulate around all three cyls as the engineers designed it.

 

[kenmyfam]

Re: One head over heating

You need to do whatever you have to if you want to keep your motor in good shape and not fry it. If one bank of cylinders is overheating then the other bank won't be far behind it. Clean it out both sides, replace deflectors and have some peace of mind. Better to deal with stripped out bolts now rather than a fried motor soon
My 2 cents.

 

[bmstang]

Re: One head over heating

I guess at one time this was a salt water boat just by the looks of the corrosion. I personally live on fresh water and only use it in fresh water i have only had it about 3 months and have done nothing but work on it. When i did the head gasket on the other head i did put in new diverters as there were only 2 in there and they were deformed like a pancake. Like i said that head is running cool and the power head is running cool. I will try it by just cleaning the cover but your right i will probably have to pull the other head and check the diverters especially after what i saw in the other head. The guy at the boat store wanted to sell me this solution for $20 that he said would get rid of all the corrosion in the motor he said you put the ears on hook up the hose and run it through the motor. I don't remember the name of it but it might be worth a shot.

 

[ezeke]

Re: One head over heating

It certainly would not hurt to use Salt-Away or other similar products for salt, but that will have little effect on cacium build-up.

No solution or product will eliminate the problem of displaced water passage deflectors and they will eventually destroy the engine if not serviced.

 

[bmstang]

Re: One head over heating

I see what your talking about thanks for the pics. The side i replaced did not have corrosion on them like that they were basically just melted. That does not mean the side i am working does not have corrosion i understand that. I am going to give it a shot by just putting the cover back on and running it as i have to put the cover back on any way.

 

[Joe Reeves]

Re: One head over heating

(Water Deflectors)
(J. Reeves)

Water deflectors are actually lengths of 3/8" outside diameter rubber hose, installed between the top cylinder and any cylinder beneath it, and also between the bottom cylinder and the block. The purpose of the deflectors is to have the water follow a definite path around the cylinder walls. Unfortunately the deflectors between the cylinders will at times swell sideways due to either a previous bad overheating problem, or simply due to age and salt corrosion. This causes a water flow restriction which usually allows the water to cool sufficently at low rpms but not at the higher rpms.

This hose material can be purchased reasonably at any automotive parts type store if you care to make your own, or you can purchase individual deflectors at any Evinrude/Johnson dealership at a somewhat higher cost.

Removing and installing them can be a hassle at times, but not always. I use a sharply pointed scribe with about 1/4" of the tip bent at a right angle whereas I can reach in, jab the tip sideways into the rubber, then yank it out. It's necessary to clean the seating surfaces where the ruber contacts the block with a small rat tail file to eliminate salt deposits etc. When installing the new rubber deflector, coat the deflector and the metal surfaces with WD40 which will act as lubrication to allow it to go in as easily as possible.

Make sure that you insert something into that deflector area before cutting and installing the deflectors if you make your own so that you will be certain that they are the right length and also that they will be seated properly. Usually a very small amount will be left extending about the block sealing area..... simply cut the excess off with a single edge razor blade.

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay auction at:

http://shop.ebay.com/Joe_OMC32/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1

 

[bmstang]

Re: One head over heating

I cleaned out the cover put it back on and didn't seem to solve the problem the way it was clogged it had to be done anyway but i guess i have to pull the head and see what is going on.

 

[191Seanymphstriper]

Re: One head over heating

Ok listen. Do it right the first time or dont do it at all........ Remove the head. Remove the other head you just re=installed. Replace all deflectors. Be sure to clean out all pathways and free up any salt deposite blockage etc. Then put her back togeather and she should be running nice and cool. Also all covers head gasket covers etc should all have proper gasketc on them.... Do this and let us know the turn out! You will be happy you did it right! Trust me!

 

[191Seanymphstriper]

Re: One head over heating

Now listen if the heads seem to be in really poor condition drop them at the machine shop and have a rebuild and and new rings, Then you will be in really good shape! If you got the extra cash,,, If your looking for a quick fix then stick to above post

 

[kenmyfam]

Re: One head over heating

i guess i have to pull the head and see what is going on.

Yes I think some of the above responses mentioned that to begin with. What a good idea !!
Do yourself a favor and do both banks of cylinders

 

[bmstang]

Re: One head over heating

I already did the other side cleaned out the jackets and put in all new deflectors. I feel good about the one side i can't keep messing with the side i did the head gasket on because every time i take a bolt out it's pulling the threads from the block side and the helicoils don't want to hold i am up to 4 holes already i don't want to mess with it anymore like i said i am pretty confident with that side. Besides the boat and motor are both 78 i need to stop somewhere i am already way behind the 8 ball compared to what the boat would be worth. Next i am going to try salt terminator to see if that helps i guess it can't hurt with the salt i seen on the water cover. I will get to taking the head off this weekend the store did not have a head gasket in stock. Thanks for all the help

 

[191Seanymphstriper]

Re: One head over heating

look online and order the gaskets etc!

 

[Joe Reeves]

Re: One head over heating

If the aluminum of the powerhead is deteriorating (head bolt threads), it's time to put that engine to rest and upgrade, or at least replace the powerhead.

With four (4) head bolts stripped and not being able to torque them, it's certain that water is going to bypass the head gasket and enter the cylinders.... just a matter of time.

 

[bmstang]

Re: One head over heating

I was afraid of that i think i am just going to use it for as long as i can if i can't sell it. I only use it, in fresh water for bass fishing i really don't need to run it hard for any length of time. The four bolts i was talking about are all on the outer edge and i don't have any water leaking out right now. They are tight just not torqued so hopefully i could get some time out of it. I am hoping if need be when the time comes i would only have to put another $20 gasket. I am getting a backfire and popping when i manually bring the rpms up with the throttle linkage only at low rpms. Now driving the boat underload she don't miss a beat runs flawless low rpms and high is the backfiring due to the head overheating or could it be in the carbs i just rebuilt them not to long ago

 

[bmstang]

Re: One head over heating

Update i just took the head off the passage ways were fairly clean nothing really to speak about. The deflectors were there but covered over with calcium and flat like a rectangle. When i took them out they broke off in little pieces they were very brittle. I cleaned everything out made sure all the passage ways were clear put it all back together and fired it up still over heating where do i go from here.

 

[emdsapmgr]

Re: One head over heating

You said the water diverters (rubber deflectors) were brittle. I assume that you replaced them with new....prior to reinstalling the heads. If it is still overheating, I'd be inclined to pull the flywheel off and remove the water passage cover on the top of the block between the two cyl banks. Have a look inside the block for any debris accumulation. Possible you have a restriction inside the block.

 

[bmstang]

Re: One head over heating

Yes i did replace them with new ones before i put the head on ran it for like 5 minutes it gets so hot when you touch the top of the head you have to pull your hand away. Like i said i am getting popping at around 2000 rpms in the idle position could it be a lean condition causing the heat in that head.