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Overheat Alarm 1990 90hp Johnson

T

the_stranger

New member
"e recently purchased this mot

"e recently purchased this motor and the test run and subsequent outing were all good.

Then the problems began.
First off was the overheat alarm going off. Flow from the pee hole was good. We pulled the cover to feel the head temp and noticed the fuel primer solenoid leaking. Upon return we pumped the fuel bulb as you normally would and noticed leaks fuel leaks from the fuel line to each carb.
Whilst repairing these we noted the each spark plug was loose.
Our thoughts were 1) we were lucky as fuel leaks and sparks are not a good idea and 2) a lean condition from air ingress about the spark plugs and into the fuel lines causing increased temperature.

So remedy this and fire it up in a bin. Ran it for ages - no problem.

Take it out and it overheated again.

So, water pump still looks strong from the pee hole, it must be thermostats right?
Remove the thermostat housing and bingo - someone had replaced one thermostat in the past but not the other. The old one came out in bits.. Looked to see if any bits were unaccounted for or lodged anywhere visible, couldn't see any.

Re-assemble and run it up. Great - unless we go over 4000 rpm, in which case the alarm goes off after 3-5 minutes.

If we stop the motor and immediately start it again, the process resets i.e. can run it all day under 4k or if taken above 4k alarm goes off again after say 3-5 minutes. Stop the motor and restart it repeats the process

Sooo. Where should I be looking?
Alarm system or is there some way to test flow around the block?"
 
"similar problem with 99 90 hp

"similar problem with 99 90 hp ocean runner,purchased last year with 30 day warranty,after picking up and trying,same thing,overheat alarm and slow mode over 4000 rpm,took back he flushed good,said he found reed grasses in t-stats.again tried,same thing,took back and he pulled t-stats and ran in river without them to flush then reinstalled,been good ever since,suggest pulling t-stats,flushing and installing new t-stats."
 
"So I ordered the SELOC manual

"So I ordered the SELOC manual for this motor as OMC in NZ say genuine is not available and I wanted to get on with it quickly.
That would appear to be a waste of time as it appears short on specs and test procedures. For example it says test the compression and tells you how, but not what the upper and lower limits are.
I also am have problems finding a definitive way to test the temperature sender units or any way to test or check for obstruction in the water galeries - or do I just strip the motor to test this?"
 
"Yes, I agree about the Seloc

"Yes, I agree about the Seloc / Clymer manuals. Alot of repetition, little specific information, and try to cover too many engines in one manual.
I have ideas on the questions you have. Please re-post and let me know if you want my input.
I'm gunshy now."
 
"Doug sir, I would love your i

"Doug sir, I would love your input please as I am lost as to an approach to take other than pulling the heads, which I would prefer not to do if I don't have to."
 
"There is no upper and lower f

"There is no upper and lower factory spec on compression, mainly that the differences between cyl's should be within 10%. Depending on cranking speed and engine temp, I would say about 90+ is within reason.
The temp switches have to be removed to be tested correctly. 'Boil' them and note the temp where they short out.
To check for obstructions in water galleries, the best is to use a heat gun. Have the lower unit in a barrel of water,NO MUFFS, start and search for hot-spots with the heat gun. If no significant spots, then impeller, thermostat and the big rubber seal for the exhaust going into lower unit might be due for change!!"
 
"Ok, some progress - I think.

"Ok, some progress - I think.

Pulled the head covers and there was quite a bit of crap in the water jackets under there - particularly on the port bank, which had felt and tested a little hotter.

I tested both temperature sensors and both tripped at 178.

Compression is 135 on each, except number 4, which is 150. Dealer says number 4 is often rebored if water gets the exhaust ports and suggests this would account for the higher compression in that cylinder.

I spoke with the local dealer (absolutely awesome guys) he says if the flow from the pee hole is strong the pump will be fine. He also suggested pulling the heads to check the rubber deflectors.

So ran up the motor after having re-installed the head covers and tested the temperature of both banks.
The starboard bank was running 10-15 degrees hotter than the port bank.
Whipped the starboard head off and was quite surprised how clean everything was in there. Bores have no lip, it looks like it has just been honed and there are no scores.

So in short I can find nothing wrong - but one thing I need to know is the position and number of rubber deflectors in the block. I can't find this information in my seloc manual."
 
"(Water Deflectors)
&

"(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 store at:

http://stores.ebay.com/Evinrude-Johnson-Outboard-Parts-etc?refid=store"
 
"Thank you for that guys.
Is

"Thank you for that guys.
Is anyone aware of any clear guide or hopefully a photo as to the exact position these deflectors should be in please?

I must admit, I feel very annoyed at having been ripped off with the seloc manual. From all accounts the deflectors are important and I would like to think that any manual worth it's salt would at least cover the important stuff. Were it not for the Internet I wouldn't even know that the deflectors existed."
 
"Deflectors..... two on a bank

"Deflectors..... two on a bank. In the water passage, one between the top and bottom cylinder (middle of bank), the other betwen the bottom cylinder and the block.

Remove the cylinder heads, you can miss them."
 
"At this juncture they are pos

"At this juncture they are positioned so as to ensure flow to/from the head is impeeded. This would seem to be counter intuitive to me, hence my desire to be careful to ensure I have it correct.

Below relates to the starboard head - this is the only one I have removed at this stage as the Port bank temps measure well below the starboard.

One is positioned between the top and bottom cylinder as you note. It is NOT central horizontally, but off the the starboard side, thus it is clear of the water port in the block between the middle of the two cylinders.

The other is as you note, at the bottom of the lower cylinder, again clear of the lower water port in the block, again to the starboard side.

This would appear to effectively create a chamber about the starboard side of the No3 cylinder. The holes in the head gasket that allow for connection of the water jackets between the head and block are into this apparent dead end chamber.

As I say, this would appear to me to be counter intuitive, however, does this sound correct to you please?"
 
"The deflectors are in the pro

"The deflectors are in the proper position, forcing water to flow up one side of the water passage and down the other side. You'll notice that there is a very slight ridge on one side of the deflectors (on the cylinders aluminum casing) that hold them in place."
 
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