Boat motor question

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  • mark71211

    Ultimate Member
    Sep 10, 2012
    2,234
    Edgewater
    I looking to buy a used 3.5hp 2stroke boat motor soon. I have been read where it’s a mixed crowd says to use trufuel cause it’s ethanol free and better for your motor. But on the other side people are saying not to get that cause trufuel is for air cooled motors and they need to run hot for that stuff to really work. So I’m wondering if anyone has used it and how does it work or just what do you think.
     

    Mark75H

    MD Wear&Carry Instructor
    Industry Partner
    MDS Supporter
    Sep 25, 2011
    17,174
    Outside the Gates
    Trufuel won't run hotter or cooler, its BS. I agree, a new injected 4 stroke will be dramatically more reliable. Its made to run on modern crap
     

    gtodave

    Member
    MDS Supporter
    Aug 14, 2007
    14,182
    Mt Airy
    I wouldn't worry about the trufuel being hotter or colder. Just make sure the mixture is accurate and you use GOOD fuel.

    Why a 3.5hp though? The only thing I can see something that small on is a dingy to pick up dead birds or move decoys
     

    Mr. Ed

    This IS my Happy Face
    MDS Supporter
    Jun 8, 2009
    7,899
    Edgewater
    Do yourself a favor. Go to Lee airport and buy aviation gas to mix for your outboard. It's expensive ($5.50/gallon last time I tanked up) but it's 100 octane, ethanol free, has lead. I use Startron for a stabilizer, and even after two years in the can it's still fresh and runs engines just fine.
     
    Last edited:

    TrappedinMD

    Active Member
    Dec 15, 2011
    856
    Western MD
    You want to use NON-ethanol gas that is as close to the octane rating as you can find that your motor was built for. I’ve seen plenty of problems from ethanol fuel. The problem is that the ethanol is hydroscopic, it will absorb water from the air. Once it absorbs water it becomes like a gel and will restrict fuel flow in carbs and clog up filters and fuel lines. Two strokes are especially susceptible because the cool the piston and lubricate using the fuel. If fuel is restricted they run hotter and get less lubrication which normally results in scored pistons + cylinder walls. High octane will not burn as efficiently in an engine designed for low octane. High octane takes longer to completely burn but if your engine isn’t high enough compression and spark advanced to use it alot goes out exhaust.
     

    pre64hunter

    Active Member
    Mar 19, 2010
    643
    Harford County
    Do they still make 2 strokes?

    Does anybody still make a 2 stroke? I'm old school and never thought I'd give up a 2 stroke but now I feel the other way. Newer motors are made for the ethanol fuel.
    I use fuel from the gas station and add Star Tron Enzyme fuel treatment, its supposed to eat up the alcohol in the fuel. I have a fair amount of experience working on 2 strokes and have an older 4 cycle Yamaha now. I had a fair amount of problems with the ethanol fuel and had to put a new carb on the 4 cycle ($450!).
    The main thing is keep the fuel fresh, add the enzyme and MOST IMPORTANT is use the TruFuel when you winterize it. I use to run the fuel out of it but now I leave fuel in the system because you can't get it all out and the little bit that's left in there will evaporate and leave moisture behind or gum up. This is the way the marinas do it. I winterize ALL my motors like this, blowers, weed eaters, 2 stroke tillers, boat engines, lawn mowers. Never had a problem since, always start up in the spring.
     

    JohnnyE

    Ultimate Member
    MDS Supporter
    Jan 18, 2013
    9,467
    MoCo
    I would think that older engines, and that would certainly include two-strokes, do not tolerate ethanol in their gasoline.

    Hop over to https://www.pure-gas.org/ to locate ethanol-free gasoline near you. The site is not the most up-to-date, so verify you can get what you need if you have to go out of your way.
     

    lazarus

    Ultimate Member
    Jun 23, 2015
    13,680
    Do yourself a favor. Go to Lee airport and buy aviation gas to mix for your outboard. It's expensive ($5.50/gallon last time I tanked up) but it's 100 octane, ethanol free, has lead. I use Startron for a stabilizer, and even after two years in the can it's still fresh and runs engines just fine.

    I would run avgas. A reason we removed lead from gas and at least in aviation uses you aren’t breathing it in directly. You are with a marine outboard. Especially something like an itty bitty 3.5hp outboard on a duck boat or whatever it is being used on.

    Plus it clogs spark plugs pretty quickly.
     

    atblis

    Ultimate Member
    May 23, 2010
    2,011
    Interesting. I had never heard that about 100LL. I haven’t experienced plug fouling in my yard tools, but they get run hard (using 100LL).

    Here’s a really interesting read
    https://www.shell.com/business-cust...entre/technical-talk/techart-18-30071600.html

    Also, I’ve always wondered why ethanol free gas was impossible to find around me. I found a mention that there’s an exclusion zone around DC for smog pollution reasons. Anybody know anything about this?
     

    Biggfoot44

    Ultimate Member
    Aug 2, 2009
    32,884
    If somebody doesn't jump in with all the details , I'll come back with the oversimplified version .
     

    atblis

    Ultimate Member
    May 23, 2010
    2,011
    Interesting, I just looked at pure-gas.com and there are a few local to me marinas selling ethanol free gas. A couple years ago I couldn't find any close by. It was either eastern shore, or way south. It looks like many were added to that site this year. Did something change?
     

    atblis

    Ultimate Member
    May 23, 2010
    2,011
    East of DC. Lots of marinas, but none selling ethanol free (eta: until recently) I always found it really odd.
     

    atblis

    Ultimate Member
    May 23, 2010
    2,011
    That’s my point. That’s recent. There are several others now. Trying to figure out what changed.
     

    johnkn

    Ultimate Member
    Feb 27, 2012
    2,113
    Always fun filling my fuel tank at the marina, Marina mark up is ~$1 a gallon so ~$5 a gallon for high test x 250 gallons, plus the Yamaha Ring Free and stabilizer. As bad as the cost was the time it takes with the slow Marina pumps. 45 minutes to fill.... LOL......

    .
     
    Last edited:

    Biggfoot44

    Ultimate Member
    Aug 2, 2009
    32,884
    Greatly simplified :

    Virtually every " Metropolitan Area" is required by EPA to have an Air Polution Abatement Plan . The relevant part to this discussion is the mandated use of Reformulated Gasoline .

    I'm not a Chemical Engineer , but simplified , one of the key specs is increased oxydisors . Ethanol is the most common , and economical EPA approved components for this . Traditionally , that meant you had to get beyond urban and suburban jurisdictions to purchase " normal formula " gas .

    Once upon a time , I compared , and there was 5% difference in mpg between Urban and Rural gasoline (both Ethanol ) . A similar difference between Summer and Winter blends .
     

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