68 evin 18hp thermostat

[Emerald14]

Hey fellas,<br /><br />1968 Evin 18hp #18803M-E02656<br />I discovered last evening that the No. 1 cylinder sparkplug is stripped on this motor that is new to me. Was using my trusty torque wrench set at the recommended in/lbs. converted to ft/lbs. Torqued the No. 2 cylinder first with no issue and the No. 1 cylinder never came tight. So, as a result, I pulled the head to repair the threads and am going to replace the thermostat, and gaskets. When examining the head cover, I noticed a port to the "port" side of the thermostat housing that is part of the water jacket. It is apporx. 5/16 to 1/4" in dia. It has a rubber plug inside. It didn't look like it belonged there and was wondering if it could have become dislogded from somewhere else and became lodged here. The rubber plug is approx. 3/8 to 1/2" long and appears to have been chewed up on the larger end.<br /><br />Any ideas??<br /><br />Thanks for your advice.<br /><br />JR

 

[Paul Moir]

Re: 68 evin 18hp thermostat

I belive the passage you're refering to is the one that bypasses the thermostat. It allows air out of the top of the block and positively allows hot water to arrive at the thermostat. I can't think of any reason you would want to plug it.<br />Is it possible it's a piece of an impeller?<br /><br />It's not unusual to strip a Johnny/Rude spark plug, as the threads are aluminium and only 3/8" long. It seems to me that when they went to 7/16" reach plugs they solved that little problem.<br /><br />That said, most ft/lb reading torque wrenches are very inaccurate at the low end of their scales, and cannot be trused. For outboard work I have a 0-250 inch/lb wrench which pretty well covers the innacurate end of my ft/lb wrench. Even calibrated deadly at 50 and 100ft/lbs, between 20 and 30 my ft/lb wrench has an error of 20% diminishing to 5%. Under 20 it gets abysmal.

 

[steelespike]

Re: 68 evin 18hp thermostat

My manual shows a seal that appears to go above the thermostat perhaps that is what you found.<br />I don't see anything else in that area like what you describe.Most likely someone will be along with definative info.

 

[Emerald14]

Re: 68 evin 18hp thermostat

PM<br />I would agree with you in regards to the bybass.<br /><br />The piece of rubber I found in this passage appears to be some type of plug, tapered on one end and as stated before the other end appears damaged. Ironically (possibly) it is the same size as the passage. I did just install a new impeller, imp housing and plate, grommet. I don't believe this mystery piece came from any of those sources. <br /><br />My theory may be similar to that of a heart attack. The rubber piece became dislodged and this is as far as it made it. <br /><br />I'm stumped.<br /><br />JR

 

[Emerald14]

Re: 68 evin 18hp thermostat

Okay then, <br /><br />Once I take this out, should I be concerned where it came from?<br /> Isn't there some type of rubber plug in the exhaust housing?? I remember it mentioned in the manual but cant find it yet.<br /><br />Also a side note:<br /> With the head removed, I was taking note of the condition of the cylinders. The marks left from the cylinder hone are still visible. It is obvious that the engine has never been overhauled per the paint on the head bolts. <br /><br />Is it safe to assume that the motor has very few hours on it??

 

[Brackishbob]

Re: 68 evin 18hp thermostat

I also have found these rubber plugs in my 1982 35hp. They are designed to control or direct the flow of water. They're supposed to be there.

 

[itstippy]

Re: 68 evin 18hp thermostat

Scratching around in my collection of old Johnson Service Bulletins I found SB #1411 from June 1976:<br />Subject: Spark Plug Wet Fouling<br />On Models: 1968 through 1973 20HP, 1969 through 1976 25HP<br />We have heard of some complaints of excessive spark plug wet fouling on 25HP engines which occurs primarily in northern states during early Spring and late Fall. This condition can usually be eliminated by:<br />1. Inserting a 203290 grommet in the by-pass hole in the cylinder head as shown in Figure 1. Since the 203290 grommet is larger than the by-pass hole, grinding approximately 1/8" off the diameter of the head will make the grommet fit the hole snugly. See figure 2.<br /><br />The diagrams show how to mutilate a rubber grommet and shove it into the bypass hole. I'd pull it out of there and hope you don't get "wet plug" syndrome like us Wisconsin boaters.