Evinrude 1988 88hp SPL - Thermostat Gasket Question

jfonk3

Recruit
Joined
Oct 26, 2009
Messages
2
Hello,

I have a Evinrude 1988 88hp SPL that I bought 3 years ago, I had the Thermostats and water pump changed, the engine runs great. I am no engine expert at all, lol...

Upon starting the boat it runs great for about 10 minutes and then then begins 'pissing' warm water and then hot water until the overheat alarm sounds.

I figured it was probably the t-stats so I changed them (and some other people recommended that as well). I've never done it before and it was a complete nightmare getting at the bolts. I used the sierra kit (18-3673) from iboats. The old t-stats were fairly corroded from being used in saltwater. I only use the boat about 20-30 hours a year, but I start it up each week for 15 or so minutes.

Upon starting the boat up again with the new t-stats and the 'ear muffs' it overheated again in the exact same way. There is a strong water stream so I assume the water pump is working properly.

Now on to the gasket question, I followed the chart in the manual exactly, used gasket sealant, etc. When I put on the second gasket (the one that attaches to the back of the engine), it slightly went on top of the 2 t-stats, less than an 1/8" around on the outside of the t-stat silver looking round cover. Would this prevent them from opening? I assume that the middle part of the t-stat (the kind of nipple that extends when you squeeze the springs.) The gaskets are no where near that part.

Let me know if that is how it's supposed to be. It was really just a slight overlap but I just want to be sure.

Thanks,
John
 

Bob_VT

Moderator & Unofficial iBoats Historian
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May 19, 2001
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26,019
Re: Evinrude 1988 88hp SPL - Thermostat Gasket Question

Okay, being a 1988 it has some years on it. I will lend a wild guess (since I went through a similar routine on my V-4 and it solved the same problem).

It is probably time to replace the water deflectors. Do some searches here on iboats and you will find posts relating to them.

I replaced my deflectors and to get to them you must remove the heads so it will cost you head gaskets too. This will also give you the chance to inspect everything and clean out your water jacket a bit.
 

DargelJohn

Petty Officer 1st Class
Joined
Feb 14, 2010
Messages
337
Re: Evinrude 1988 88hp SPL - Thermostat Gasket Question

I have a 1996 Johnson 88SPL, and you are describing the exact problem I had.

I totally rebuilt this engine. After the rebuild, I kept getting a hot horn while on the water muffs. Checking with an IR gun, it was always the right bank (starboard) side getting hot. Back plate would start out cold, then get hot and the hot horn go off. The problem was totally random and just about drove me nuts.

Reading on the web, I ran across a post talking about the t-stat block and the two pin holes that are close to the center, in recessed areas, on each side. The post talked about drilling those out to about twice the size or 1/8". These holes are there to displace the cold water in the t-stat chambers, to allow warm to enter from the heads, opening the t-stats. If these holes become clogged, then the hot water from the heads back up and does not allow the t-stats to open quickly enough, causing the overheat.

I bought a used t-stat housing/block from E-Bay and tested this theory. Have not had any trouble since....

FYI - I put the t-stat gaskets on dry, no sealant. Hope all this helps, I know how frustrating this problem can be.
 

jfonk3

Recruit
Joined
Oct 26, 2009
Messages
2
Re: Evinrude 1988 88hp SPL - Thermostat Gasket Question

Thanks everyone for your help. I'll definitely consider changing the water deflectors.

About my gasket question do you think i should be concerned with the gasket overlapping the t-stats that little bit? Or is that fine and I shouldn't worry about it?

Thanks again,
John
 
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