Small outboard motor running rough - found the problem!

Scubagirl62

Scubagirl62

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Mar 13, 2011
82
Seaward Fox 19 Lakeview, Ohio
We have a small outboard on our Hunter 23.5. We weren't able to get her in the water last year so she sat on the trailer. We had winterized the motor. Everything seemed fine this spring until we gave the motor more gas. She started really running rough! It had always been a good little motor. We had the carb rebuilt a couple years back and she had done just fine. This year something was different. Yeah! We had decided to bypass the boat gas dock and just mix the gas ourselves. It would appear that these smaller outboards do not do well with gas from the filling station due to the ethynol content. After going back to regular "boat gas" we've had no issue with her. Just wanted to get that out there in case someone else was having a similar issue and was scratching their head.
 
Stu Jackson

Stu Jackson

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Feb 26, 2004
22,986
Catalina 34 224 Maple Bay, BC, Canada
Ethanol has been the bane of boaters since it was introduced. Nothing new here. Want to know more? Check out the BoatUS website.
 
C

CaptDon01

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Nov 19, 2008
2,129
Catalina C-22 MK-II Parrish, FL
Ethanol blends are nothing new, and the outboard manufacturers are well aware of this. Try running the outboard with a heavy dose of Seafoam, like a whole can in a 3 gallon tank of fresh premium fuel with Stabil added as per directions. Best if you can just let the outboard run at a fast idle all afternoon or longer, (on the boat tied up in a slip and left in gear is the best), and then continue to use up the fuel. I've suggested this often as a solution before making adjustments of rebuilding the carburetor. My outboard starts easily, and will idle smoothly all day long, even my little 2 HP Honda for the dinghy that sits in the garage and only gets used once or twice a year.
I use a "maintenance" mix of about 1/3 can of Seafoam, and Stabil per 3 gallons of premium fuel, and use it in not only my outboards, but my generator, and power washer. These sit for months and months and will start right up, and run with no issues. Wal Mart has the best prices on Seafoam, (except no substitute), at about $7. a can.

All I run in my outboards and small engines is Shell or Chevron premium with my "snake oil" mixture. My list of believers has grown long and prestigious.

Don
 
seadaddler

seadaddler

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Dec 19, 2006
5,818
Hunter 36 Punta Gorda
I also learned the hard way to use only Ethanol Free gas
and oil mix for my 8hp 2 stroke with plenty sea foam and just started it today since last year and it runs great.
 
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S

Steve Dion

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Dec 2, 1999
15,184
Hunter Vision-36 Rio Vista, CA.
I just purchased a gas power washer (Honda engine). The instructions recommended using a product called Ethanol Shield on each/every tank of fuel.

Another option would be to use aviation fuel from the local airport if you can get access to it.

We have a Tohatsu 18hp 2 stroke and have been having issues because of fuel for the last 2 years. I would suggest that you clean out the jets and see if it runs any better.
 
flynhi4u

flynhi4u

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Oct 28, 2013
678
Hunter 20 Lake Monroe
I run Nothing but a avgas in all my small engines. Same weed eater for 23 years. Finally changed the plug because I thought it probably needed it.
Sadly, avgas as we know it is about to become history, but even it's replacement will be far better than anything you can get out of a pump on the street.
Sam in IN
 
Daveinet

Daveinet

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Sep 20, 2014
1,328
Rob Legg RL24 Chain O'Lakes
This past year I switched to a mixture of 1/3rd sulferic acid and 2/3rds distilled water. My outboard has never run better.
 
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Daveinet

Daveinet

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Sep 20, 2014
1,328
Rob Legg RL24 Chain O'Lakes
I'll just let you think about that for a while. See if you can figure it out.
 
seadaddler

seadaddler

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Dec 19, 2006
5,818
Hunter 36 Punta Gorda
I just looked at my post and meant to say
Ethonal Free Gas.
I almost went with electric dinghy motor but the charging problem stopped me.
I found out it was cheaper to just buy a new carb for Yamaha 8hp I think it was $125
and $80 twice at the repair shop and it would still not always run very good.
I now always use Ethonal free gas and seafoam every tank and the last 3 years starts
right up after sitting for 3 months.
Nick
 
MaryEllaRose

MaryEllaRose

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Sep 11, 2013
244
Catalina 25 6106 Lake Erie Metro Park
Does the same hold true for four stroke outboards? My 9.9 Tohatsu (new last spring) ran great all summer. I ran plain old regular straight from the pump. My slip neighbors 9.9 Mercury (same motor, made by
Tohatsu) was problematic to say least when he could it started. I'm just curious as to what to expect next spring.
 
JohnVTX

JohnVTX

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Jul 14, 2015
840
Catalina 30 Stillhouse Hollow Marina
MaryEllaRose said:
Does the same hold true for four stroke outboards? My 9.9 Tohatsu (new last spring) ran great all summer. I ran plain old regular straight from the pump. My slip neighbors 9.9 Mercury (same motor, made by
Tohatsu) was problematic to say least when he could it started. I'm just curious as to what to expect next spring.
Click to expand
I have a Tohatsu 6hp 4 stroke. I made this change last week and motor immediately ran great. Would not run without 1/2 choke before making change.
 
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