15 HP Evinrude help - No power or rpms

[wmk0002]

Thanks for the info and reassurance guys. I will definitely do the full conversion later on, not just the carb.

As of now, I'm moving back to trying to get the 15hp going. At least if I get that running right I can run it on my hull and know for sure how a 15hp should really perform on it.

Speaking of the 15hp, yesterday I tried to remove the flywheel to check everything out under there but was left hanging as my puller kit didn't have bolts that would fit in the smaller holes. So I visually checked out the exhaust passage on the leg and it looked good. Then rechecked cold compression and got about 108 psi on each cylinder. I still need to check the fuel pump condition but aside from that my next priority is going to get some grade 8 bolts to pull the flywheel with.

 

[wmk0002]

It has been a while since I fooled with this motor but finally figured out why I mysteriously lost spark. Turns out the powerpack died on me. Swapped it out with the one off of my 9.9hp and I now have thick spark jumping a 1/2" gap.

Is it possible a failing powerpack could have been my problem all along? Possibly somehow weakening the spark as rpms went up? I know they are the brains of the ignition system but not sure what all symptoms a failing one can cause.

 

[wmk0002]

Finally ran the motor with the known good powerpack in a barrel and it ran well. I will boat test it sometime in the next few days and report back.

 

[wmk0002]

Victory at last!

I lake tested the motor yesterday after work and it opened up wide open and climbed to WOT rpms. I saw 17 mph but didn't have my tach on to get rpm readings. This was with the 9.9 hp carb on it so my speed is right on par with what the 9.9 hp motor was producing on this boat.

To recap what I did... I changed the plugs, installed new OEM coils and plug wires, and put on a known good powerpack. Based on no performance changes from the new plugs, wires, and coils I would say that I had a bad powerpack all along. Based on the unburnt fuel on the lower plug, it seemed to be failing at higher speed and producing very weak to no spark on the bottom cylinder. Whatever was causing this problem eventually totally failed when the powerpack died altogether.

Now I just need to order a new/used powerpack and put the 15hp carb back on and this motor should be good to go for another 35 years lol.

I appreciate the help from everyone!

 

[finstr]

Congrats on finding your problem. I just found this thread and was thinking as I'm reading the issues that the power pack unit you describe sounds remarkably like an ignition module from an automobile. They're responsible for not only firing the coils but firing them at the correct time. The ignition advance curve is programmed into them and sometimes as in your case the ignition won't advance thus creating a serious lack of power and rpm. And they are impossible to bench test. I'm not sure if it's possible to run a timing light on an outboard even to check maximum advance. Like a lot of automotive manuals will state..."Replace with known good part" lol. I love that.

PS. It's very possible that the arcing coils damaged the unit. I've seen that many times in the automotive field.

 

[Stumpalump]

That vintage power pack biodegrades. Changed one on the advise of seaway marine when I tuned up an 83 that ran poorly. Johnson and Evenrude dropped the price of the units to drown out the cheap China knockoffs. I think the bad coil issue was for the older stuff but people always swap coils first because it's a no brainier. On 80's OMC the power packs are a known biodegrade issue. I'm buying a 6hp today that does not run. Wish me luck.

 

[wmk0002]

That vintage power pack biodegrades. Changed one on the advise of seaway marine when I tuned up an 83 that ran poorly. Johnson and Evenrude dropped the price of the units to drown out the cheap China knockoffs. I think the bad coil issue was for the older stuff but people always swap coils first because it's a no brainier. On 80's OMC the power packs are a known biodegrade issue. I'm buying a 6hp today that does not run. Wish me luck.

Didn't know that. Right now I'm deciding if I should buy a used one off of Ebay for about $30 or buy a new OEM or CDI Electronics one for $60. I will be selling this motor so right now I am leaning towards the used one.

 

[Stumpalump]

I have a "good" used one as well. Good enough to get it started. Spend the 60 bucks. That thing will fire up by just looking at the pull starter with a new one. That will help you get top dollar for it later and no hassles with a potentially bad part now.