1989 or '90 Merc 15-plug gap - The Hull Truth

sokolj · 08-04-2008, 04:33 PM

The motor had been on its side in an unheated garage for over two years. I used fresh fuel and oil. With the help of some starter spray it started and ran for twenty minutes. Amazing! An hour later it was stone dead.
I dumped the fuel in the filter bowl and inspected the filter. It was dirty and contained some black "goo" Maybe the fuel line bulb is disintegrating. Ordered a new filter- put the old one back-for now. Ordered a new fuel line with bulb. I pulled the NGK plugs and wiped them with a towel-put 'em back. I have run the engine up and down the river for the last three days. Runs like new. Got a couple of AC Marine plugs to replace the old plugs if needed.
------What is the correct gap?
------How am I doing?
Thanks!

A1 Outboard · 08-06-2008, 05:53 AM

It looks like the gap is .060" according to NGK

Keep an ear tuned to the motor, any hesitation, surging, or poor idle means that the carb and possibly fuel pump should be cleaned or replaced. Also inspect the tank for debris and water.

sokolj · 08-06-2008, 06:15 AM

Many thanks! Would the gap be the same on the AC Marine plugs?