Help stuck on boat.

[Dieseldude]

Originally Posted by ebisucapt

So in the ICW I managed somehow to find the only rock in a cut. Well I bent/broke a prop. Waiting for new one. Well previously to this the out board on my dingy quit working. It has a bad misfire and tends to stall and when given gas wants to die. 3.5 HP Merc 4 stroke.

It has a new carb and I have removed it and cleaned it three times. With no difference. I disconnected the kill wire. checked the valve adjustment. (Sorta don't have feeler gauges with me). I am thinking a coil but not sure. And for some odd reason the coils for this motor are nearly $300 a bit much to buy to experiment with. I am anchored out in Charleston and can't get out to get anything.

Really scared to go to a marina with one engine on Monday with the currents around here but have no choice as My prop came in and having a diver change it.

Just wondering if anybody else thinks a coil can cause this problem in my outboard?

I once had a similar problem with a mower. Engine would die after a few minutes for no known reason. I tried all ordinary troubleshooting ideas. Finally had to give in and take it it to a shop. The mechanic had seen this problem before. The ignition wire had a small crack in the insulation that you really had to look hard to see. The wire and coil were one unit, and quite expensive. The mechanic covered the cracked area with black electrical tape. Problem solved. No telling if this is your problem, but worth having a very close look ate the ignition wire. Also good to thoroughly clean the spark plug boot on the wire and the spark plug ceramic insulator area. These can accumulate dirt that can short out the high voltage. Dirt can accumulate along the length of the ignition wire that could short high voltage. Be careful with solvents that might damage the insulation. Real electrical contact cleaner or methyl or isopropol alcohol should be ok.

[Paulpdf]

Honestly, I am not sure. If you are getting spark I would doubt its the coil. Sounds like the carb to me. I am close to Charleston, about 30 miles inland. if I can help with info about the area I am familiar.But I believe its the carb.Wish I could be more help. Paul

[Boatyarddog]

Originally Posted by ebisucapt

So in the ICW I managed somehow to find the only rock in a cut. Well I bent/broke a prop. Waiting for new one. Well previously to this the out board on my dingy quit working. It has a bad misfire and tends to stall and when given gas wants to die. 3.5 HP Merc 4 stroke.

It has a new carb and I have removed it and cleaned it three times. With no difference. I disconnected the kill wire. checked the valve adjustment. (Sorta don't have feeler gauges with me). I am thinking a coil but not sure. And for some odd reason the coils for this motor are nearly $300 a bit much to buy to experiment with. I am anchored out in Charleston and can't get out to get anything.

Really scared to go to a marina with one engine on Monday with the currents around here but have no choice as My prop came in and having a diver change it.

Just wondering if anybody else thinks a coil can cause this problem in my outboard?

Lean condition causes misfire, cutout on acceleration.
Be sure your adjustment are correct, your pump is pushing fuel, filter is clean.
Look at the plug.
Is it white on the tip, or black.
This an tell you a lot.
Boatyarddog

[donradcliffe]

I'd drain the carburetor bowl, then fire it up at night and look for arcing. I did have a Tohatsu coil go partially bad once, and spent way too much time trying to diagnose it.

[Dieseldude]

Originally Posted by Boatyarddog

Lean condition causes misfire, cutout on acceleration.
Be sure your adjustment are correct, your pump is pushing fuel, filter is clean.
Look at the plug.
Is it white on the tip, or black.
This an tell you a lot.
Boatyarddog

Good point on lean fuel mixture. The engine will lack power upon acceleration and stall. May run rough before shutting down. Despite having dismantled and cleaned, needle could be sticking closed. These are finicky. Perhaps float is jamming or the needle spring is defective. Did you make sure that the jets are well cleaned? Will need to run through with a very small round prod such as a strand of wire.


An intake air leak can be the cause of a lean mixture. Is the carburetor well seated on its gasket? Is there any other opening that air could be sucking through?

[gonesail]

Originally Posted by srbaum

Your Mercury 3.5 four stroke is really a Tohatsu, with a Mercury decal. Buy Tohatsu parts for your outboard for less, then paying for Mercury parts, purchased though Tohatsu and labeled as Mercury.

also many parts aren't even available for the older Mercs .. but you can still get the Tohatsu parts