1990 88 SPL overheat alarm when full throttle HELP

dereck_coons

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Mar 13, 2011
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20
OK I have replaced: Impeller, plugs, wires, thermostats, fuel pump, she is running great except after about 30 seconds at full throttle the overheat alarm goes off and if I back it down to idle it goes off in about 10 seconds. **** stream is good seems like pump is working as it should. Do the sensors ever go bad, I was thinking of getting one of those fancy point and shoot thermometers and checking temp when alarm goes, or am I overlooking something else that may be bad. Can the timing if not set correct cause the motor to run too lean and overheat?? Any ideas would help, thanks.
 

Joe Reeves

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Feb 24, 2002
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13,262
Re: 1990 88 SPL overheat alarm when full throttle HELP

Always possible that something was overlooked within the water pump repair, however.......

(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.
 

emdsapmgr

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Dec 9, 2005
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11,551
Re: 1990 88 SPL overheat alarm when full throttle HELP

Some engines will accumlate debris inside the water passages. Sand, weeds, salt corrosion, etc. That accumulation (restriction) can cause overheats at high speed. It's easy to check for this by pulling the head covers off. (not the actual heads) If the passages inside the heads look bad, then you should then pull the heads and inspect around the cylinders-inspect for water flow restrictions-esp keeping in mine Joe's comments above.
 

dereck_coons

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Mar 13, 2011
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Re: 1990 88 SPL overheat alarm when full throttle HELP

OK I have priced the parts and it looks like its another hundred bucks, Im going to pull the cover off the heads inspect, remove the head if they look gunky, replace the temp sensors and the little rubber check valves, and all gaskets. But first I will drop the lower unit and re check the impeller job making sure all rubber gaskets and seals are properly set. Thanks for the tips guys, there is no way I could afford owning a boat without forums like these to help me keep it running!! will post back in a couple of weeks with results.
 

dereck_coons

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Mar 13, 2011
Messages
20
Re: 1990 88 SPL overheat alarm when full throttle HELP

Removed the port head today, broke 6 cover bolts trying to get her off Yikes. Sure enough the deflectors were really bad. the top one pulled right out but the bottom required some redneck macgyver , I ended up using a drywall screw to thread into the deflector about an inch and pulled her right out. Now its time to let the lube work on the broken bolts and then e-z out them tomorrow morning. Is there anything that I can spray into the water jacket housing to clean all the crud out? How clean does it have to get?
 

dereck_coons

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Joined
Mar 13, 2011
Messages
20
Re: 1990 88 SPL overheat alarm when full throttle HELP

Hey Joe you were right, replaced deflectors, cleaned all parts, new gaskets, six broken cover plate bolts, and a helicoil later the head is back on and she ran great all weekend. Took me and friends camping on island all weekend, alarm never went off once. Thanks.
 

Joe Reeves

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Feb 24, 2002
Messages
13,262
Re: 1990 88 SPL overheat alarm when full throttle HELP

Another happy customer :)
 
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