Pontoon Boat & Deck Boat Forum

Greetings to all . . .

I seem to be having problems with an "unstable" outboard. I have a 1996 Tracker 120 Force 2-stroke with recently cleaned carbs. The engine is running quite erratic -- rpm's jumping anywhere from 800-3500 -- while in neutral. While I am glad the engine starts and is not constantly stalling, I am wondering if the problem may be the kind of gas I am putting into the engine. I am using 87 octane and I believe it has up to 10% Ethanol.

Would running 89 or 93 octane be a better choice ? Should I add octane booster or a different additive to the fuel to clean out the jets ? I realize I probably should just tear down the carbs and put new jet kits in them (probably been a while since they have been replaced).

Any thoughts to help stabilize the engine for the time being ? All inputs would be greatly appreciated . . .

Those engines are not made to run ethanol. The fuel lines carb parts will melt or fall apart using it. I recommend you stop and use a mid grade gasoline only

lakerunner wrote:Those engines are not made to run ethanol. The fuel lines carb parts will melt or fall apart using it. I recommend you stop and use a mid grade gasoline only

lakerunner... question for you, the last time I filled up my boat was at the neighborhood mobil station and after I filled the boat up I noticed a little sticker on the pump that said the gas was 10% ethanol... so 2 questions, 1- can 10 percent ethanol be harmful to a 4 stroke and 2- would using "stabil" or some product of that nature help with that problem? Thanks!

I am in NH and all gas is 10% ethanol here. The marinas sell valtech gas that has a bunch of addatives but is still 10% ethanol. So it can't be detrimental to the engine or anything else. Higher octane fuel shroud not matter unless you are running really High compression. Check out the valvtech website it is pretty informative.

If I got it right, when you put your engine in neutral and w/o giving it throttle your rpm’s go from 800 (normal idle) to 3500 and back again. That has nothing to do with the gas itself but rather a leaning condition. Your carbs are not getting enough gas at idle.
1.) Check your fuel delivery i.e. fuel pump, lines, filters, bulb and such. Look for a pinched line or cracked full lines. The fuel pump blub is usually a prime suspect.

2.) If possible run a separate fuel tank with separate lines directly to the engine. If the problem goes away then that's your problem.

3.) Are your carbs synced?

4.) You may want to turn your mixture screw on you carbs to the left which should richen up your fuel ratio.

ROLAND wrote:

lakerunner wrote:Those engines are not made to run ethanol. The fuel lines carb parts will melt or fall apart using it. I recommend you stop and use a mid grade gasoline only

lakerunner... question for you, the last time I filled up my boat was at the neighborhood mobil station and after I filled the boat up I noticed a little sticker on the pump that said the gas was 10% ethanol... so 2 questions, 1- can 10 percent ethanol be harmful to a 4 stroke and 2- would using "stabil" or some product of that nature help with that problem? Thanks!

I am sure your motor is ethanol friendly, my E-Tec is but still don't want to use it. Not sure about using stabil but for long term storage or non use the ethanol could separate. So my advice is if you don't have one I would install a water separator just in case

slingshot wrote:If I got it right, when you put your engine in neutral and w/o giving it throttle your rpm’s go from 800 (normal idle) to 3500 and back again. That has nothing to do with the gas itself but rather a leaning condition. Your carbs are not getting enough gas at idle.
1.) Check your fuel delivery i.e. fuel pump, lines, filters, bulb and such. Look for a pinched line or cracked full lines. The fuel pump blub is usually a prime suspect.

2.) If possible run a separate fuel tank with separate lines directly to the engine. If the problem goes away then that's your problem.

3.) Are your carbs synced?

4.) You may want to turn your mixture screw on you carbs to the left which should richen up your fuel ratio.

All good points . . . I should also mention that the fuel line has been replaced and is new. I'm not sure about synced carbs other than there is a rod that works both at the same time through a single throttle cable (I think that is what you mean). If I understand the concept, you are saying that if the rpm's start racing upward, that is a sign of less gas than normal getting into the engine ???

On another note, I thought that if the gas station has gas with up to 10% Ethanol in it, it is all the grades of fuel that will have it. Is it the concensus of the people here to run 89 octane instead of 87 octane ??

Thanks for the info -- this is helping me out . . .

1roadking wrote:...but is still 10% ethanol. So it can't be detrimental to the engine or anything else.

Octane is used to prevent detonation (knocking) in higher compression engines. Assuming your outboard has no performance work done like a milled head or high compression pistons you don't need anything above 87 unless the engine manufacturer calls for it which would mean that they built the engine with higher compression components than normal. Again, what you described doesn't sound like its fuel quality related.

ethanol, in engine building circles, is a high performance fuel and allows you to build extremely high compression engines as long as you only run them on alcohol (pure ethanol is rated at approx. 106 octane). All components of an alcohol race car are built to withstand the corrosive effects of alcohol i.e. fuel tank, lines, carb or injectors and so on. If you try to run petroleum in that same engine you'll blow it Kingdome come (detonation). The problem with 10% ethanol is that that you’re running that corrosive ethanol, although in a reduced amount, in a fuel system that isn't designed to deal with its corrosive effects.

FloterBoter wrote:

1roadking wrote:...but is still 10% ethanol. So it can't be detrimental to the engine or anything else.

Yep...check out my "well there's your problem thread":

viewtopic.php?f=2&t=2284&hilit=so+there+s+your+problem

Guys, non of the marinas here offer non ethanol fuel that I am aware of. I run it in my cars, boat, atv's, lawn mower, sleds and generator. When I store my stuff, I put fuel stabilizer in it. The valvtec gas has the addatives in it from the pump. I agree, ethanol needs stabalizer if you are going to have it sit. But I think with stabalizer it is fine. I don't believe we can get non ethanol fuel here in ne. If so, I have not seen it. My point is, don't panic through some stabilizer in it if you are not going to use it up within in a few months. Have you guys heard of the valvtec gas? It is suppose to be the solution up here. This is my 1st boat and u guys are freaking me out man.

ethanol in gasoline is a political "solution". it has nothing to do with reducing carbon footprint.
lots of o-rings and seals need to be changed to run with it safely.
it is the worst thing to happen to older marine engines that i can remember.
tell the fucking liberals to let us drill our own oil reserves and we won't
need to be eating our food supply and wrecking our older engines.

The damage to my fuel hose was caused by ethanol being incompatible with the "ethanol resistant" fuel hose. It was fresh fuel. My marina had a ton of boats disabled because of ethanol fuel last year. Boat US confirmed this and paid an insurance claim on it.

Ethanol fuel isn't the problem. The first internal combustion engines ran on 100 percent ethanol. It's incompatible fuel lines, tanks, seals, o-rings etc. that cause issues. I had to replace my carb, hoses, and fuel pump on a 3 year old boat.

That sucks hope I don't have the sane problems

To add a little fuel to fire (so to speak), that 10% could vary considerably, depending upon the blending method (splash or metered). Our local newspaper did "an investigative" report a couple of years ago(?) and found some stations ethanol was actually closer to 20%. And our gas stations do not have to label the pumps one way or the other. However, the marinas typically do not sell ethanol tainted gas.