- This topic has 19 replies, 7 voices, and was last updated 2 years, 10 months ago by
.
-
Hi All,
I sold a few of my old Johnson motors and in lack of better judgment I took this 15 HP Evinrude as partial trade. The Evinrude has a cooling issue, I replaced the complete impeller, housing, base plate , seals ect. Still the same issue, very little water flow. I removed the thermostat housing and the old thermostat and found the opening behind the thermostat partly clogged, so I cleaned that and blew compressed air thru the complete motor, it appears to flow air thru the complete cooling system. We’ll see . My question is there was a spring inside the thermostat housing between the housing and the thermostat , has anyone seen this type of set up before?? None of the parts diagrams show this spring but it appears to be holding the thermostat against the head. I am not sure whether this is the correct thermostat or not, temperature of 143 stamped into it. , I cleaned it up and put it in hot water and it opened. Just not sure about that spring, any help would be appreciated.
Thanks,
RJ
The spring is there because it allows the thermostat to lift off its seat at higher speeds, for additional cooling. 143 degrees is correct. 15s are great motors with one big problem: Over time, the upper water tube grommet under the power head gets pushed in by corrosion and blocks a great deal of water flow, which will lead to overheating. It is an odd situation because often, you can’t tell this is happening by just looking at the tell tale output. If it were my engine I would spend the time, pull the power head and clean this area up, replacing the grommet. You’ll also need the power head base gasket. Have a propane or Mapp gas torch ready. You may need it on the inner exhaust housing/tuner bolts. Then again, you might not, if you’re lucky.
Long live American manufacturing!
1 user thanked author for this post.
Rusted Junk: billw is 100% correct. Your issue is the UPPER WATER TUBE GROMMET !! Follow his advice, then your overheating issue will be HISTORY. I had an identical problem with a 9.9 last season.
1 user thanked author for this post.
Like Bill says, chances are good that you have a grommet issue, especially if this engine has seen salt water use. Adding insult to injury, this 15hp may have two pesky grommets. Later model 15hps like yours have an “open inner exhaust tube”, along with a short water tube exiting the powerhead….
That being said, I am assuming that you cleared out the overboard indicator hose and plastic restrictor nipple, oftentimes these are plugged…Surely don’t want you to pull this thing all apart needlessly.
And yes, like Bill says, that spring belongs there, allowing the thermostat to lift off its seat at higher RPMs, so more water flows through the powerhead, bypassing the thermostat. Be sure to order the new rubber seal, and be sure the SS cap is in place over the new seal. Carefully clean out the thermostat pocket so the thermostat won’t be stuck and can move freely off its seat, once water pressure can overcome the spring pressure.
In spite of some unforgiveable issues, these are great engines. The powerhead and gearcase are very robust. The cheesy plastic throttle gears are a pain, and the cooling system needs regular maintenance when used in salt water. Be sure that little water drain in the bottom of the gearcase is thoroughly cleaned out while you have the gearcase off, you may want to enlarge that drain hole a little bit as well…1 user thanked author for this post.
Thank you all,
I did find the parts diagram and see the spring,retainer, gasket and thermostat, I have these .ordered. I am a where of the grommet issue and may have to pull the power head to fix that, but I’ll put the thermostat in and see if I get lucky , the passage to the upper over flow hole is clear, if I blow compressed air thru it I can feel and hear the air coming out the water pickup on the lower unit, so we’ll see. Next is the issue with the the throttle gears in the handle with broken cogs , the plastic gears inside the cowling don’t seam to be broken but I am sure they are worn.looks like those parts aren’t cheap. This is the little motor that keeps on giving I guess.
Thanks again for the advise.
RJYour 1983 has the head with the thermos at the bottom unless one has put on a later year head. The early heads ran 143F all the time. Maybe that’s the confusion with the thermos and your manual. Later years used the head with the thermos on top that lifts off during higher water pressures.
1 user thanked author for this post.
Well, I hope you do get lucky and don’t have to attack the grommets…Didn’t mean to jump the gun, guess I have seen too many of these. I remember the first one I discovered back in 1981. Just want to make sure I understand your post…The engine didn’t pump well before you replaced the water pump, correct? Any possibility that the water tube is misaligned and not going into the impeller housing grommet correctly? Perhaps someone bent up the water tube on a previous attempt. Perhaps the intake screen is plugged up with debris from your test tank. This engine “looks” fairly clean, has it been used in salt water? The gear housing castings are very thin under the forward part of the SS impeller plate, and erode badly….This might be causing the pump to suck air instead of water…Don’t get this confused with the other scalloped cut out under the impeller housing that is supposed to be there…
You can be fooled by using compressed air to blow through the water tube…The compressed air usually has enough pressure to “open up” the grommet allowing air through it, whereas the water pump doesn’t develop that much water pressure….Keep in mind that this 15hp probably uses the two water tube set up I mentioned in my earlier post, so if the outlet grommet was collapsed, you would still feel air coming out the telltale hose blowing through the intake water tube.
Again, I want to be wrong, so feel free to ask plenty of questions and provide any more info that might help us help you…I surely don’t want you to pull the thing apart needlessly….The grommet job isn’t too bad on fresh water engines, but salty ones usually require the torch…Sometimes trying to pry that powerhead off the exhaust housing can be a challenge also, be careful not to break the motor pan with pry bars.
There is a way to install the new grommets “improperly” that will avoid this issue in the future, hopefully we won’t get that far and it will pump fine with the new thermostat….Don1 user thanked author for this post.
Are you using an OMC impeller? The 15s and 9.9s are the only motors I ‘ve worked on where Sierra impellers, even with a new Sierra housing, do not pump at slow trolling idle. On three late 1980s motors I found this and the OMC impeller fixed it.
Dave1 user thanked author for this post.
Are you using an OMC impeller? The 15s and 9.9s are the only motors I ‘ve worked on where Sierra impellers, even with a new Sierra housing, do not pump at slow trolling idle. On three late 1980s motors I found this and the OMC impeller fixed it.
DaveGood point indeed!
1 user thanked author for this post.
- You must be logged in to reply to this topic.
