What have I done? (79 4hp Chrysler)

flyingduck

Cadet
Joined
Oct 30, 2005
Messages
7
I found a Chrysler 4hp saltwater outboard on Craig's List for $100. Model number is 42H9F. The guy ran it for me in a tub for a minute or two so it seemed to be in good working order so I bought it.

The gas tank seemed to have some varnish in it so I removed it, filled it with paint thinner and metal nuts to get the varnish out. Then I emptied the thinner and nuts out of it. Wasn't sure if I'd gotten it all so I added a fuel filter to the fuel line just in case.

In the interest of maximizing performance I installed what was supposedly a compatible NGK iridium spark plug.

When I put it on my little 8 foot boat (fresh gas premixed at 50:1) that I use for crabbing, it fired right up and seemed to run like a champ. Then it started slowly losing power and eventually quit, putting up a little smoke from the back. Once it had cooled a bit I tried starting it up again and it did start but didn't seem to have the power it originally had. Once again power fell, it died and put up a little more smoke. I haven't messed with it since.

Any clues as to what's going on here? Was it possibly too hot of a plug? What might be going on with this motor and how might I remedy it? Or should I just give up on it and go searching for another outboard?
 

walk-on

Petty Officer 2nd Class
Joined
Aug 16, 2006
Messages
112
Re: What have I done? (79 4hp Chrysler)

I had an old Evinrude duckhunter 3hp that did a similar thing. It ran great for about a hundred yards then died. Started up and ran for a couple seconds then died. I found a vent on the top of the gas cap that needed to be open, otherwise it was starved for fuel. Keep in mind that I opened the vent before I left the ramp, but the vibration of the motor allowed it to screw itself back in and seal.
 

flyingduck

Cadet
Joined
Oct 30, 2005
Messages
7
Re: What have I done? (79 4hp Chrysler)

I'm going to go back to a normal plug to see if that helps. It looks like a Champion L86C is the right plug. Anybody know what the correct gap is?
 

Turn4fun

Petty Officer 3rd Class
Joined
Jul 25, 2009
Messages
76
Re: What have I done? (79 4hp Chrysler)

My Seloc manual recommends L86 for the 4 HP. L86C is used in the 6 HP, not sure what the difference is. Gap is .030". Your engine also has the highest idle speed of any Chrysler outboard at 800-1000 RPM.
 
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