HELP!!! 90 hp merc '78 model won't start

[jimc]

HELP!!! 90 hp merc '78 model won't start

Could someone offer some simple basic suggestions? Got a 78 model 90 hp merc w /distrubutor. have good spark at all plugs, but will not fire, just cranks. any help appreciated Jim

 

[12Footer]

Re: HELP!!! 90 hp merc '78 model won't start

Re: HELP!!! 90 hp merc '78 model won't start

Get a clean spray bottle with 50:1 mix in it.<br />Spray a couple squirts directly into the carbs intake,and try to start it. If it fires, then oyu know it's fuel-related.<br />Take the fuel line off the carb.Pull the plug wires, and put the fuel line end into a plastic bottle. See if it puts-out fuel. If it does not, the fuel pump is not werkin. If it does, you proly got a plugged idle jet.<br /><br /><br /><br />------------------<br />I'm no expert, but I DID sleep at a Holiday Inn last night!

 

[Capt Ron]

Re: HELP!!! 90 hp merc '78 model won't start

Re: HELP!!! 90 hp merc '78 model won't start

Were the plugs wet w/gas when you pulled them. I had the same problem with my '74 650, fire, gas, and compression but no start. The gap the fire should jump is about 7/16" and you should use a spark tester to check this. It takes alot more power from the coil to fire the plugs during the compression stroke. They may fire great while out of the cylinders. Also check the grounds and the starter may be lowering the voltage to the point of being unable to fire the plugs while starting. I found the aftermarket coil was bad and replaced it with an OMC coil that I had bought 10 years ago but never used. I made the screw end for the coil wire on my lathe. The motor runs great now.<br />BTW, the bad coil was part of the power pack/coil unit from CDI. The bottom nut on the switch box damaged the coil as a result of a design flaw and they advised to use the OMC coil as a replacement.<br />Good Luck,<br />Capt Ron

 

[Capt Ron]

Re: HELP!!! 90 hp merc '78 model won't start

Re: HELP!!! 90 hp merc '78 model won't start

One more thing, I found the coil problem by cranking the engine in the dark and looking for arcing.<br />Also, use an ohm meter to check each plug lead and the coil lead between the cap and the plug or coil ends. I had one bad plug wire too. <br />Capt Ron

 

[Capt Ron]

Re: HELP!!! 90 hp merc '78 model won't start

Re: HELP!!! 90 hp merc '78 model won't start

12footer,<br />It's Holiday Inn Express and I sleep with the #4 top rated reservation agent, doesn't make me an expert either but she probably booked your reservation.<br />Capt Ron

 

[jimc]

Re: HELP!!! 90 hp merc '78 model won't start

Re: HELP!!! 90 hp merc '78 model won't start

I got the it started, thank you. I hooked up a water hose to the water intake as suggested by the manual, but hardly anything comes out the water exhaust, but then I only let it run a second, just enoughto see if would start. The problem was the enternal wiring harnass was not allowing enough voltage for the coil to produce adequate spark. The harnass was badly corrided, and not wanting to spend $150 for 1 moded plug and 8 short wires, I found the plug at WW Grainger Electrical Supply, and built a harnass. thanks again Jim

 

[Capt Ron]

Re: HELP!!! 90 hp merc '78 model won't start

Re: HELP!!! 90 hp merc '78 model won't start

That's great Jim.<br />Capt Ron