Skip to content

The easiest fix ever for your ethanol plagued outboard boat engine!

August 1, 2009

I have a vintage 1960 Crosby 17′ “Fish & Ski” runabout boat with a 1985 25HP Mercury outboard on it and it is purring like a kitten now. It wasn’t always that way, before ethanol was introduced into our gasoline it ran great but the summer of 2007 was horrible. We would all show up at the landing in Chatham, MA for a day of boating and an hour & half later retreat home after a few skinned knuckles and a lot of praise for the lord….

That summer I rebuilt the carburetor 2 times, had it off the engine probably a dozen times, while floating in various different but scenic locations. The problem was that the needle valve connected to the float in the carburetor bowl would get stuck in the closed position and no gasoline could get into the bowl. To salvage the last part of the summer, I ended up bending the float linkage so that the valve was open all the time. This made it interesting, it was fire it up and go boating! Idling was not an option as the gasoline slick created behind the boat was sure to attract the attention of the environmental police.

The summer of 2008 we didn’t even bother to launch the boat as I had the use of my fathers boat. Which was fine but no where near the same fun ride. So this spring I started looking for new carburetor parts for the old 1985 outboard and there are some available but not the parts I needed. It was looking like time for a new outboard. Then my father suggested I call a local mechanic/guru “Barry Fulcher” which I did. I explained my problem and he said ah yes, old Mercury’s were prone to this dilemma when subjected to ethanol. He had a customer that had a old 150HP Mercury and all of the carburetors would starve for fuel. The reason was that the needle valve would not get any lubrication because of the ethanol.

Now follows the easiest fix ever, they put “Marvel Mystery Oil” in with the gasoline and the old 150HP outboard ran great. So I rebent the carburetor float linkage back into its correct position, added “Marvel Mystery Oil” to the gasoline. Now you have to understand my 1985 25HP Mercury outboard did not receive the kindest of care after the 2007 season, had not run since then, anyway I squeezed the fuel line bulb and turned the key. The engine fired up immediately!! The only other thing I have done to the outboard was adjust the idle needle valve a 1/4 turn and now everytime we show up at the landing for a day of boating on the “Crusty”, we go boating!

If you are having similar problems with your outboard no matter what make or HP please try this easy fix. I add 16 oz of “Marvel Mystery Oil” to every 6 Gals of gasoline along with the normal amount of 2 cycle oil. The outboard smokes a little more at start up but clears up when running. I hope this helps you out and gets you out on the water!

1960 Crosby 17' Fish & Ski The "Crusty"

1960 Crosby 17' Fish & Ski The "Crusty"

If you are interested in Nautical stuff please click on the photo above or link below to go to CaptJimsCar-go an eBay store that specializes in High Quality Nautical Decor such as fully assembled model ships & sailboats, very large teak ships wheels, metal decorative anchors, globe home bars and more!

CaptJimsCar-go for High Quality Nautical Decor

Capt Jims Nautical Cargo same High Quality but Lower Prices

One Comment leave one →


  1. Fathers

Leave a Reply

Please log in using one of these methods to post your comment: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: