1974 Evinrude 15hp runs rough.

[jedtfd]

Hello out there. This is my first time posting and I hope someone might have an idea of what I can do to fix the problem. I bought this motor from someone I know. It was running when I got it but not great. Took it in for a tuneup thinking it would fix the problem. Still ran rough. Took it back to a different mechanic who said the electrical needed replacing to the tune of 500. Not worth putting that kind of money into it. I let it sit last year and now I have deceided to try things myself. First I started with the lower end and everything looks good there. Next I am going to do a compression test. Does anyone know what a good compression for this motor would be? If it is in a good range, what should I do next.

Thanks for any advice,
jedtfd

 

[kevin11mic]

Re: 1974 Evinrude 15hp runs rough.

i just got rid of a 1978 25 that ran great and both cylinders were arround 120

 

[kbait]

Re: 1974 Evinrude 15hp runs rough.

Get a spark tester and check for 1/4" blue bolt in open air. If you've got that, and new/good plugs gapped to .030", your spark is fine, and I'd look to the fuel delivery side. If spark is marginal, pull flywheel and remove, clean (file 'em up shiny), and reinstall, gapping to .020" and see where you're at. You may want to install new condensers, they do fail, but rarely in my experience. If you get 50+ on compression, It should run. Good luck!

 

[jmendoza]

Re: 1974 Evinrude 15hp runs rough.

If the ignition is OK, and compression fine, sometimes a mechanic will clean the carb, but not remove the welch plug and so it still has crud in the low speed circuit, causing erratic running.

If the compression is off, it could also be just a blown head gasket, which is a cheap fix. Usually one plug will be wet if this is the case.

intermittant spark is usually a bad condensor, sometimes a coil. You can swap coils easily to eliminate them as a problem. Points can get sticky, make sure they move freely and are not corroded, and properly gapped. You can fine tune them later for full power using a static timing light or meter, but first just get the engine running smoothly.

On engines with electric start and an alternator, the magneto plate bushing can get worn so badly it causes the timing to become erratic, make sure the magneto plate is not really wobbly, a little play is normal however.

The $500.00 estimate was to make you, and your engine go away, typical!!

Lotsa good guys here that know this engine really well, so keep us posted

 

[jedtfd]

Re: 1974 Evinrude 15hp runs rough.

Get a spark tester and check for 1/4" blue bolt in open air. If you've got that, and new/good plugs gapped to .030", your spark is fine, and I'd look to the fuel delivery side. If spark is marginal, pull flywheel and remove, clean (file 'em up shiny), and reinstall, gapping to .020" and see where you're at. You may want to install new condensers, they do fail, but rarely in my experience. If you get 50+ on compression, It should run. Good luck!

Thanks for all the info. I checked the compression and get 104 in each cylinder. I will get to the other tests you advised.

 

[jedtfd]

Re: 1974 Evinrude 15hp runs rough.

If the ignition is OK, and compression fine, sometimes a mechanic will clean the carb, but not remove the welch plug and so it still has crud in the low speed circuit, causing erratic running.

If the compression is off, it could also be just a blown head gasket, which is a cheap fix. Usually one plug will be wet if this is the case.

intermittant spark is usually a bad condensor, sometimes a coil. You can swap coils easily to eliminate them as a problem. Points can get sticky, make sure they move freely and are not corroded, and properly gapped. You can fine tune them later for full power using a static timing light or meter, but first just get the engine running smoothly.

On engines with electric start and an alternator, the magneto plate bushing can get worn so badly it causes the timing to become erratic, make sure the magneto plate is not really wobbly, a little play is normal however.

The $500.00 estimate was to make you, and your engine go away, typical!!

Lotsa good guys here that know this engine really well, so keep us posted

Hello JMendoza, Thanks for all your help. First, could you tell me what a Welch Plug is and where do I find it. I checked the compression today and I have 104 in each. The two coils look like they are new. The motor has electric start but no alternator. The motor starts easy but when its running there seems to be a miss, and when I had it out last it wouldnt go full throttle. I will continue with the other checks you mentioned and appreciate all your help.
Thanks again, jedtfd

 

[flintcreek]

Re: 1974 Evinrude 15hp runs rough.

The Welch plug is a aluminum plug that is driven in the carb to seal a opening that is used during machining and can be removed to clean the carb. Carb kits come with new plugs. There should be one in the top of the carb at about the end of the low speed needle, when you take it out you can see the holes in the low speed circuit. Hope this helps. Make sure you have good fire on both cylinders, these little motors will run on 1 cylinder but not have the correct amount of power. Buy and adjustable spark tester from a auto parts store should jump spark around 3/8".

Good luck.
Flintcreek

 

[jedtfd]

Re: 1974 Evinrude 15hp runs rough.

The Welch plug is a aluminum plug that is driven in the carb to seal a opening that is used during machining and can be removed to clean the carb. Carb kits come with new plugs. There should be one in the top of the carb at about the end of the low speed needle, when you take it out you can see the holes in the low speed circuit. Hope this helps. Make sure you have good fire on both cylinders, these little motors will run on 1 cylinder but not have the correct amount of power. Buy and adjustable spark tester from a auto parts store should jump spark around 3/8".

Good luck.
Flintcreek

Thanks for the advice. I will check that the spark is a good one.

 

[raczekp1]

Re: 1974 Evinrude 15hp runs rough.

its good to read: http://www.sschapterpsa.com/ramblings/Ramblings.html

OB Tips On Buying a Used Outboard Motor
2 OB Picking a Marine Mechanic
3 OB Frequently Asked Outboard Motor Questions
4 OB Gasoline & Outboard Oils
5 OB Store a Boat With a Empty or Full Fuel Tank ??
6 OB Outboard Motor Transom height / shaft Length
7 OB Basics on Starting an Motor That is Resisting
8 OB Neptune Mighty Might 1.7 hp 1956 Outboard Restoration Project
9 OB Elgin 2.5 hp 1947 Outboard Restoration Project
10 OB Mercury 4.5 hp 1975 - 1985, Getting it Running Again
11 OB Johnson / Evinrude Year/Model Code Identification
12 OB Johnson 10 hp QD Series Motors 1949 - 1963
13 OB Johnson / Evinrude 6 hp 1969 - 1979
14 OB Johnson / Evinrude 8 hp 1992 version
15 OB Johnson / Evinrude 9.5 hp Normal Repairs 1964 - 1973
16 OB Johnson / Evinrude 9.9 /15 hp 1974 - 1976 Magneto Ignition
17 OB Johnson/Evinrude 9.9 / 15 hp General Info & Normal Repairs 1974 - 1992
18 OB Johnson/Evinrude 9.9 / 15 hp Powerhead / Midsection Repairs
19 OB Johnson/Evinrude 9.9 / 15 hp Carburetor / Fuel Pump Repairs
20 OB Johnson/Evinrude 9.9 / 15 hp Lower Unit / Water Pump 1974 - 2005
21 OB Johnson/Evinrude 9.9 / 15 hp Water Circulation Problems
22 OB Johnson/Evinrude 9.9 / 15 hp Troubleshooting
23 OB Johnson/Evinrude 9.9 / 15 hp Converting Shaft Lengths 1974 - 2005
24 OB Johnson/Evinrude 9.9 / 15 hp Converting to Electric Start 1974 - 1992
25 OB Johnson/Evinrude 9.9 / 15 hp Normal Repairs 1993 - 2005
26 OB Johnson/Evinrude 9.9 / 15 hp Converting to Electric Start 1993 - 2005
27 OB e-Bay Motor Rebuild & Why it Blew a Piston After a Rebuild
28 OB

 

[bonzoscott]

Re: 1974 Evinrude 15hp runs rough.

I believe kbait failed to mention "points" after flywheel removal.

 

[kbait]

Re: 1974 Evinrude 15hp runs rough.

Righto Bonzo!
Also, Your motor does have a charge coil under the flywheel (standard on e-start models). Those '74-'76 points motors w/e-start (9.9-15hp) had a problem w/that particular setup developing lateral play in the armature plate, and that directly changes the point gap. Check to make SURE you don't have much lateral (side to side) play in that plate. I hear they had a fix from the factory, but is no longer available. The charge coil puts quite a bit of extra 'yank' on the armature plate due to the extra magnetic force from the flywheel on each revolution. If you have this issue, post back and I'll detail how I 'fixed' it to useable..

 

[jedtfd]

Re: 1974 Evinrude 15hp runs rough.

Righto Bonzo!
Also, Your motor does have a charge coil under the flywheel (standard on e-start models). Those '74-'76 points motors w/e-start (9.9-15hp) had a problem w/that particular setup developing lateral play in the armature plate, and that directly changes the point gap. Check to make SURE you don't have much lateral (side to side) play in that plate. I hear they had a fix from the factory, but is no longer available. The charge coil puts quite a bit of extra 'yank' on the armature plate due to the extra magnetic force from the flywheel on each revolution. If you have this issue, post back and I'll detail how I 'fixed' it to useable..

Thanks kbait, I'll let you know how I do.

 

[gransee]

Re: 1974 Evinrude 15hp runs rough.

The thread with that reczekp1 posted is awesome! I was having problems getting the timing set perfectly on my 1975 25hp johnson motor until i read his post. I had been setting them to .020 just like everyone says but it still wasnt running right. Bought a multimeter and set the points with that and now she runs like a champ. Only problem is there is movement in the armature plate and i think that causes the points to be thrown off just a little, especially after being on the water for a while. Is there any way to fix this lateral movement problem?
Thanks

 

[gransee]

Re: 1974 Evinrude 15hp runs rough.

Kbait, can you explain to me how to fix the lateral movement problem. I am almost certain I have been fighting with this for months now after reading your post. Ive reset and reset the points. Once reset it runs great then after running for a bit it starts to run funny. I wiggled the armature plate and it DOES feel like there is movement there. my motor is a 1975 johnson 25hp. thanks, Aaron

 

[Xcusme]

Re: 1974 Evinrude 15hp runs rough.

Aaron, you might find what you're looking for here:
Evinrude 25 1975 Armature plate wiggle

http://forums.iboats.com/showthread.php?t=90303&highlight=Evinrude+25+1975+Armature+plate+wiggle\

Btw....you'll get more responses by not hijacking a thread ...just thought you'd know.
Good Luck!!