Motor skipping after trolling

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fishjunky

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I have a 2009 Honda four stroke 20 hp manual start that was bought used with low hours. It has performed flawlessly, other than being a little cold natured (take 3-5 pulls to start first time). I always have run non ethanol 87 with marine stabil added.

It unfortunately sat for three or four months or so without being run. The engine oil was changed during this time. I can't remember if I ran the carb dry at the end of the last use.

I took it to the lake last weekend. It started on the 6th pull and ran great for the first hour and a half trolling at idle speed. At this point I was going to run to another spot. When trying to get on plane the motor would be strong for several seconds and then lose power and then recover. This happened a lot of times.

At this point I basically stopped fishing and just ran the motor hoping the problem would clear itself. The motor would shut off at idle speeds. And skip at higher speeds. The longer I drove around, the better it got, but it never completely resolved itself.

The gas looks fine but am thinking about starting with fresh. I pulled the plugs and they are not fouled I don't think but also don't look new either.

My plan of action is to run seafoam through it and then check the plugs and possibly replace them.

Is the seafoam a good idea? I was planning to unscrew the pickup tube from the tank and put a seafoam gas mix into another container and draw from that. What's a good ratio of mix? I don't want to have too much mix. The motor will idle forever on a thimble full of gas.

Any thoughts are appreciated.
 
The sea foam won't hurt anything. As I was reading your post I was thinking of Seafoam. Mix ratio is on the can. If I remember correctly they have a recommended first time ratio that is about twice as strong as their recommendation for routine use. I used it every few months in my old v-4 johnson and it would smoke like a tar kiln for about the whole tank, but would clear up on the next tank and run nice and smooth until I carb'd it back up trolling.
 
Clean the carb.

After sitting that long, it's almost guaranteed that the fuel has begun to start restricting flow through an orifice or two. Maybe not enough to totally make it stop, but these 4 stroke motors have such small passages in the carb that it takes nothing to restrict fuel flow through them. Sea foam won't fix it 99% of the time. Not much will and here's my theory on this. If fuel won't flow through the orifices, how's Seafoam going to get into them to "clean" them? Especially if those orifices are above the fuel level in the bowl(s)-and the important orifices usually are.

My experiences tell us that after fuel sits for about 2 weeks or more, I can tell there's a difference in how the engine runs. From 2 weeks to about a month and a half, it'll run but not "normal". After that, it just gets worse.
 
I wound up running a 2:1 gas to seafoam mix through it for appx an hour on the muffs. Then ran the carb dry and put in new spark plugs. The old ones looked disgusting like ones from a two stroke. They did not look like this prior to seafoam (a little carbon tinged but not covered in ooze like after treatment).

Took it to the lake next day and was a little sputtery at first but once I got on plane and ran around a little, it ran perfectly the rest of the day. It also ran about 1.5-2 mph faster at top end than usual.

Not sure if seafoam is the silver bullet or not, but I'm happy the motor is running strong again.

And yes I ran the carb dry before loading the boat :)
 
I put seafoam in the tank as the stabilizer. The stabil I had was over two years old anyway.

It's cheap for my boat because it sips fuel, but on a large engine, particularly a two stroke, you would go broke buying seafoam trying to keep it at recommended levels.
 

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