1983 Evinrude 15

[Supersportster]

Hey, I have been having an issue where the motor runs great at high speeds, but slowly dies off if trolling.

I have tried all of the obvious, carb cleaning, check and replaced one cracked coil, tried different power pack taht was known to be good, used different gas tanks...

So finally I took it to a shop, and they said the compression is even on both cylinders, but a little lower then when its new???

Also they said my problem is that the thermo stats are stuck open and that is waht is causing my issue. They said the heads have to come off to replace the t-stats.

Does this sound correct? How big of a job is it for me to tackle?

thanks!

 

[Tim Wagner]

Re: 1983 Evinrude 15

Id rebuild the fuel pump first. Its cheap to do.
Oh, dont forget about this guys website. its in the sticky's.
Hope im not stepping over the line
http://www.sschapterpsa.com/ramblings/OMC/OMC info.htm

 

[Supersportster]

Re: 1983 Evinrude 15

I forgot to mention that I did rebuild the fuel pump, and changed all the fuel lines with new proper fuel lines...

 

[Joe Reeves]

Re: 1983 Evinrude 15

Yes, unfortunately the cylinder head does need to be removed in order to replace the thermostat properly, BUT I serious doubt that this is your problem. However if your engine does not warm up, stays running cold, bringing into issue that the thermostat is indeed faulty, have it replaced as that can result in other problems.

Although you've rebuilt the fuel pump, check it for diaphragm leakage as follows. And also try pumping the fuel primer bulb constantly (acting as a manual fuel pump) to see if that cures the problem.

(Fuel Pump Diaphragm Test)
(Two Hose Type Only)
(J. Reeves)

Note: This pertains only to the regular Two Hose type fuel pumps.

Leave the hoses attached to the fuel pump. Remove only the two screws that attach the fuel pump to the powerhead. Re-insert those two screws and install a nut to each of them so that the fuel pump is securely clamped together. With the fuel line attached to the engine, pump the primer bulb while observing the pressure/vacuum operating hole on the back side of the fuel pump. Should any fuel leak out that hole, the diaphragm is faulty.

If the diaphragm is faulty, the fuel pump will require rebuilding or replacing. Note that repair kits are not available for all fuel pumps, in which case replacing the pump would be necessary.

 

[ONERCBOATER]

Re: 1983 Evinrude 15

this may sound strange, but if thermostat doesnt fix problem may be idle circuit, would suggest a seafoam treatment in fuel. Also have you adjusted low speed fuel mix, it changes as the temperature of engine changes and may fix your issue. I have an 83 as well, and found that if i run it just a tad richer than i want to that she will idle all day long.

Sean

 

[jmendoza]

Re: 1983 Evinrude 15

I would not bother with all the above, instead, first fire up the engine and see if the block gets warm with the cover off. After 5 minutes, it should be uncomfortable to keep your hand on the head for more than a few seconds. If it's cool, or barely warm, pull the head and replace the thermostat. Get a new thermostat w/ seal, thermostat cover gasket, and head gasket. Be advised if the area where the round rubber thermostat seal goes is corroded, it will not seal and over cool, mine was like this and I replaced the head. This is a very easy operation to do, should only take about 30 minutes if you have all the parts.

 

[bktheking]

Re: 1983 Evinrude 15

That sounds like a crock of you know what. Motors ran without stats all day long back in the day, a motors that has a stat that is stuck open will run regardless of engine temp. Stuck closed and it would overhead and blow the headgasket. Sounds like it's more of an ignition (powerpack) or pickup sensor issue than a stat.

 

[jmendoza]

Re: 1983 Evinrude 15

Please have the courtesy to let those who have experienced this try and help him, as that is the main focus here: helping him.

If Johnson Evinrude 9.9-15 HP engines from 1974 onwards do not need a thermostat, then why do they have them? pray tell? Why do they go to such great lengths in the service manual to have you use the special temperature crayons to verify the high and low temperature arange of the block? Why did my engine always foul plugs when slowing from a high speed run to a troll? Why did it need a choke to re-start after running for 4 miles at full throttle? Why did it keep fouling plugs each time out? Why were the lower piston skirts worn away? All due to running too cold, and no thermostat. Putting in a thermostat cured all these problems. Take yours out if you do not beleive me! No offense, just want to show there is a logical and well thought out answer here that is backed up by actual factual evidence.

Here is another posters response to a guy with no thermostst on a 15(optsyeagle) that backs up what I said:
The motor also needs a thermostat. Most likely the water is pretty cold wherever you are and the T-stat is to ensure the motor warms up to about 140F. Without one and running at low RPMs, you will definitely keep fouling plugs. If I were trolling a lot, I would go with the NGK B6HS, a grade hotter plug, and I would install a T-stat no matter how fast I was going.

My matra for proper repair proceedures is as follows:
1. Identify problem and it's symptoms
2. Test for proper operation of each of the engines systems.
3. Eliminate the working systems and focus on those systems that failed the test to diagnose.
4. Test each component in the faulty system to isolate the cause of the problem, and replace.
5. I dentify the cause of the failure, as replacing the part without curing the cause will result in another failure.

 

[bktheking]

Re: 1983 Evinrude 15

Jmendonza, I never said it didn't need it , I said it would run without it (I have a 10hp in my garage that will idle all day, no stat). My focus is to always help out those who post and because I state that I don't believe a missing stat would cause a motor not to idle but would allow it to run at high speed you discredit mine and everyone elses advice?

Telling the owner that the head has to come off is another piece of misleading information, more labour and more parts, you know and I know the head doesn't have to be removed. A properly tuned motor with a working thermostat will always operate better, better gas mileage and better idle but no idle at all doesn't add up. We had a no idle situation on here not long ago and it ended up being the carb itself (scanman).


In order to gain access to the stat you need to remove the water cover on the back of the head, it's held on by 8 bolts, you do not need to remove the cowl latch but you can if you need more room. Remove the cover (make note there is a spring and metal retainer) and inspect the old stat vs the new, you'll know right away if it's stuck open, they actually can break depending on the design. Clean off the mating surface of both the cover and the head. You will need a new seal and thermostat and gasket:

0323582 SEAL,Thermostat
0378065 THERMOSTAT
0321387 GASKET,Water cover


Try replacing it a report back.


Cheers

Red circles depict bolts, green is where the stat sits once you get the cover off, one of the bolts in the pic is hidden under the fuel line I believe.

 

[mjrhoads]

Re: 1983 Evinrude 15

Jmendonza, I never said it didn't need it , I said it would run without it (I have a 10hp in my garage that will idle all day, no stat). My focus is to always help out those who post and because I state that I don't believe a missing stat would cause a motor not to idle but would allow it to run at high speed you discredit mine and everyone elses advice?

Telling the owner that the head has to come off is another piece of misleading information, more labour and more parts, you know and I know the head doesn't have to be removed. A properly tuned motor with a working thermostat will always operate better, better gas mileage and better idle but no idle at all doesn't add up. We had a no idle situation on here not long ago and it ended up being the carb itself (scanman).


In order to gain access to the stat you need to remove the water cover on the back of the head, it's held on by 8 bolts, you do not need to remove the cowl latch but you can if you need more room. Remove the cover (make note there is a spring and metal retainer) and inspect the old stat vs the new, you'll know right away if it's stuck open, they actually can break depending on the design. Clean off the mating surface of both the cover and the head. You will need a new seal and thermostat and gasket:

0323582 SEAL,Thermostat
0378065 THERMOSTAT
0321387 GASKET,Water cover


Try replacing it a report back.


Cheers

Red circles depict bolts, green is where the stat sits once you get the cover off, one of the bolts in the pic is hidden under the fuel line I believe.

So did you guys come to any conclusions on this theard???

FYI - I have a 1988 John 15HP, that does the same thing (runs excellent at ~ 1/3 throttle all the way up to full throttle), but will NOT idle! I have: 1) rebuilt the carb. 2) rebuilt the fuel pump. 3) replaced the Thermostat. 4) replaced fuel/fuel tank. 5) replaced cam follower.

Any other ideas?

 

[mjrhoads]

Re: 1983 Evinrude 15

So did you guys come to any conclusions on this thread???

FYI - I have a 1988 John 15HP, that does the same thing (runs excellent at ~ 1/3 throttle all the way up to full throttle), but will NOT idle! I have: 1) rebuilt the carb. 2) rebuilt the fuel pump. 3) replaced the Thermostat. 4) replaced fuel/fuel tank. 5) replaced cam follower.

Any other ideas?

 

[dew2]

Re: 1983 Evinrude 15

How bout if the spark plug gap was opened to .35 maybe a bit more?
What do the plugs look like? wet and fouled out?

 

[mjrhoads]

Re: 1983 Evinrude 15

Forgot to mention that. I did replace the plugs with new NGK's (with the proper GAP), and they seem to look fine (not wet for sure)....

But should I do any further analysis? Like look at them after running wide open for awhile vs. trying to struggle at maintaining a low idle?

Also, the engine doesn's sputter, backfire, etc. when i'm trying to get it to idle. It just dies, almost like you hit the kill button. Plus I can seem to make it idle somewhat by playing with the choke.

Thanks for any suggestions!

 

[dew2]

Re: 1983 Evinrude 15

If playing with the chock helps that leads me to believe its a fuel delivery problem.Just for fun open the plug gap to .35 and open the slow speed needle 1/4 turn,Please my curiosity.As I have a 1988 15 evin, that I also will be using for troling this year,I'm still iced over so I cant do it YET>

 

[ONERCBOATER]

Re: 1983 Evinrude 15

I would suggest that you run the champion plugs that the motor was designed to use, NGK not exactly the same. I agree with dew2 on the idle/low speed mixture needing to be richer. What i did with mine after link and synch was fired up cold, adjusted idle screw (had to pull the handle part off to adjust properly it was set wrong to start with) then when warmed up to operating temp I adjusted idle speed to perfect idle then set that as middle mark... I then move idle mix to max open fire engine and put back to center when warm, i can idle all day long if i choose to this way. and rarely ever need to choke except when it has sat for a few days or is very cold.
suggest reading this site the Machinist has been kind enough to offer an incredible wealth of information, and the asnswers to 99.9% of 9.9-15hp johnyrude issues. He explains clearly and concisely the how to's the why for's and the little quirks of these motors. and yes he covers tune ups, trouble shooting, inspection, decarb, you name it.
http://www.sschapterpsa.com/ramblings/Johnson 9.9_15.htm
I treat that site as my bible for the johnyrude 9.9 to 15hps.

Sean

 

[mjrhoads]

Re: 1983 Evinrude 15

Hmmm. I've all ready got my plugs gapped to .040. My Seloc manual says 1971 to 1981 0.030, 1982 and later 0.040!

 

[mjrhoads]

Re: 1983 Evinrude 15

Yep. I've done everything to date, based on that "ramblings" site.... Still to no avail

 

[mjrhoads]

Re: 1983 Evinrude 15

Also, if the choke helps, couldn't that mean possibly two things? Either, not enough fuel (so need less air via the choke butterfly), or the right amount of fuel but to much air <via some sort of air leak>, so when the choke is applied, again less air?

 

[Will Bark]

Re: 1983 Evinrude 15

When you rebuilt the carb you did pop the welch plug and clean the idle circuit holes under there with cleaner and a piece of thin wire? Scanman had done all of that and it still didn't work; I did it on mine and that was the problem; put my carb on Scanman's motor and was perfect. Go figure. BKTHEKING has scanmans carb and I haven't heard if he ever found anything actually wrong with it.

 

[Rick.]

Re: 1983 Evinrude 15

Lots of great ideas above. One thing that comes to mind, Have you done a linc and sync? If it's out it could be causing your problem. Best of luck. Rick.