Thread: Outboards and ethanol

I've been having a helluva time keeping my Merc 9.9 hp (4 stroke manual start) idling properly. If I adjust it to idle properly, it cuts out when I apply throttle. If I adjust it to run at throttle, it idles extremely rough. I have been told this might be due to the ethanol content in summer gas. Does that sound right? It definately has been using ethanol enhanced gas lately - and that's when the problems started.

Anyways, I took my motor to the service department at Outdoor World to be checked out and I ended up trading it for a new 15 hp 4 stroke with electric start. I'm wondering if I might have problems with my new motor if ethanol is the culprit. Is there an additive I should be using? Or is it unlikely ethanol is the problem?

Thanks.

All the new motors are engineered to run on ethanol gas. You shouldn't have any problems at all. In fact the only confirmed ethanol related problem I have heard of is with the mid 90's Mercs. They used rubber check valves in the fuel pumps and the ethanol causes the edges of them to curl up.

To be safe install a 10 micron water seperator type filter between your tank and the motor.

Also, keep your tank full. There is much less of a chance for ethanol to absorb moisture and and for the moisture to separate in the tank when it is full.

Ethanol is not a problem. The water that can separate from it in the tank can be.

I use a fuel/water separating filter and Stabil religiously. Haven't had any problems yet. (knock on wood) :D

Hey Chimp, as I understand it the mixture is designed to run on any modern combustion engine. If it works on your lawn mower and your 69 Biscane but not your OB.... They say on small engines 99% of all your fuel related problems start at the carb. I personally haven't seen a difference on any of my gear.

After reading your post I did some research on ethanol enhanced gasoline and I am disturbed at what I found out. From what I read water is a problem because of the ethanol and if you have a fibreglass tank (pre mid 80s, mines a 1984) you may have problems with the ethanol weakening the fibreglass. Other problems come from the ethanol loosening up built up gunk in the bottom of the tank. This can result in plugged up filters and carbon build up on valves. None of this may apply to your situation but I'm certainly concerned about my old boat. Thanks for posting about the ethanol because it would have never crossed my mind. Do all states have ethenal enhanced gas?

Originally Posted by reelcrappie

Do all states have ethenal enhanced gas?

I was told it's only in heavily populated cities and that you can go out to the sticks to get gas that does not have it in it. Anyone know if this is true?

The Exxon where I buy gas does, indeed, have a sticker on the pump that says the gas has 10% ethonal.

I have a plastic gas tank. The engine is/was 2 years 3 months old. Hopefully, BPS will tune it up (I already treated it to new spark plugs, oil, gear lube and grease) and sell it quickly. I'm looking forward to my new motor, a little more power, but especially not pulling on a starting cord anymore.

By the way, when you buy a new motor, how is it delivered? I mean when I go to pick it up, will it still be in the box? I will have to fill it with oil and gear lube? That's not a problem, but I am curious and I never asked the salesman.

Originally Posted by TapOut64

I was told it's only in heavily populated cities and that you can go out to the sticks to get gas that does not have it in it. Anyone know if this is true?

It used to be that way but I don't think it is any more. I'll check the next time I go down to Moyock.

Do the service stations have to post it somewhere that they are selling ethanol?
I haven't seen any out this way...