90 horse TOHATSU

" Motor ony reaches 4200 rpm o

" Motor ony reaches 4200 rpm out of usuall 5400. Pulled plugs & cleaned ran fine two times out, yesterday started motor and same thing, pulled plugs and found that the top two plugs where burning perfect nice dry brown color the bottom plug was wet as if getting gas but not spark, switched plug same thing.I was thinking it might be a bad coil or wire from the coil. Any thoughts? This is three cylinder 1990 90HP. "

" Bob,

It sounds like you h

" Bob,

It sounds like you have weak spark in the lower cylinder. See if you can get the spark to jump a gap about 7/16 in.

A spark tester is very handy at times like this, because it enables you to see the spark in all wires at the same time easily. Then you can tell if the spark is intermittent in one or more wires.

You can rig a tester that will do this, it just takes more time.

Tony "

" Tony, Thanks for the reply.

" Tony, Thanks for the reply. What sort of tester lets you see spark in all wires at the same time? The only tester I've used is one for a briggs & stratton ( one end hooks to the wire and the other end clamps to the plug, or to a head bolt with a window inbetween where you see the spark) one plug at a time. Thanks again. Bob "

" Bob,

The spark tester I h

" Bob,

The spark tester I have clamps onto the engine (ground), and has adjustable gaps. Each gap has a spark plug wire with an end that will fit into the plug wire boot on the engine. This way I can test for spark in all cylinders at the same time.

It is a simple thing and with a little ingenuity, one can be made. They cost about $60 and can be purchased from most outboard dealers. If you do a lot of engine work, it is a good investment. It saves lots of time when checking for spark, and enables you to find some problems quickly.

Tony "

" Tony,

That sounds like a

" Tony,

That sounds like a great tool, even though I have three different motors I cant justify the cost.I think I can test one at a time and then see if I can buy a shop manual, otherwise I will have to pay the $75.00 an hour labor + $60.00 for a coil. OH WELL I guess thats what owning a boat is all about. And its not like my Father never warned me.
Thanks again.
Bob "

" Tony,

I talked to the mar

" Tony,

I talked to the marina that sold the motor back in '90 and they said I could use there tester, sounds just like the one you described. Not only that they charge $55.00 per hour labor. I'm leaving work early today and drive out and do a compression check then do the spark check Saturday or Sunday. I'll post my findings on Monday am.
Bob "

" Tony,
I went and did the c

" Tony,
I went and did the compression check and had 120 pounds on all 3 cylinders so I would think I'm fine there, didn't have a chance to get the tester from the marina so I used my small one and the spark looked about the same on all three, I put new plugs in started and ran fine for 20 minutes then surged a couple of times and died, started and died again then would not restart. I switched over to my full tank got it restarted and it has ran fine twice now,at this point I am thinking maybe BAD GAS. I toped off with fresh gas that I treatrd with Stabill and will pull the other tank and clean and install new fuel/water seperator.
Thanks for Your time.
Bob "