1992 johnson 150 fast strike overheating

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If you ain't first you're last

Cadet
Joined
Oct 11, 2018
Messages
13
I recently got a new outboard and went to test it out yesterday starts and ran great ran it for about 20 minutes between all speeds head back to the trailer and the temp alarm went off while idling waiting to load. Today I got the infrared thermometer out hook it up to muffs to temp check the heads to make sure it was actually overheating and it was and fast. Smeed to pee ok.Got up to 200 in just a few seconds shut it off and took the lower off. Checked the impeller and it seemed fine there was some sand that I cleaned out. Took the thermostats out and they looked fine as well. Tested them and the opened at 160ish. Ran the hose down from the head to try and flush anything out and water seemed to travel no problem. Screwed the hose in from the pee hole and flushed down from there. Fyi I had the thermostats out and open and after 30 seconds to a minute water built up to the top of the heads and was flowing inside them fine. Ran the hose up the lower and flushed up. Put everything back together and Still overheating. I'll order new thermostats and impeller tomorrow when the shop opens just to be safe but want to see if I missed anything or if anyone knows any tricks? Thanks for the help guys
 
Joe Reeves

Joe Reeves

Supreme Mariner
Joined
Feb 24, 2002
Messages
13,262
Always possible that the cause of overheating is due to swollen water deflectors, especially if one bank is running hotter than the other.
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(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.
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Bosunsmate

Bosunsmate

Admiral
Joined
Apr 7, 2012
Messages
6,135
Does that model have the thermostat housing with the hole in the middle?
If so i always double that in size at least
 
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