Issue of modify.

[JohnsonM50]

While the OMC 31.8 is on a few threads lately, Ive adapted a 2 barrel from an OMC 85 to one & got it within a mph of my fastest single barrel. Its been shelved for awhile but is again ready to run. A problem I have is if it sits for more than a week or 10 days the gas in the float bowl goes south & gets the bad gas smell & of course wont fire. Its easy to drain off & prime new gas in but it should last longer.
Why?, is my question & my theory is as a stock application the 85 has a tight airbox but my mod has only a spray sheild. Could the air box be limiting the vent air entering the float chamber? This is not an alky-gas problem since it happens to av gas too.

http://i35.photobucket.com/albums/d151/mes355/DSCN0835.jpg (http://s35.photobucket.com/user/mes355/media/DSCN0835.jpg.html)

http://i35.photobucket.com/albums/d151/mes355/DSCN0820.jpg (http://s35.photobucket.com/user/mes355/media/DSCN0820.jpg.html)

[zul8tr]

Add some Stabil to the fuel, can't hurt can help like chicken soup. Are you using a E based fuel, no good? Not sure about the venting causing thre issue. Is there any evidence of water in the fuel when you clean out the bowl?

[shenders]

M50
Just disconnect fuel line and run carb. dry before you take it out of the water. never put an outboard up with fuel in the carb.

[David Mason]

Probably the water that is in todays fuels. You might also have some cheap gas in your area, who knows. But no, it is not normal around here. I simply dissconnect the fuel line from the engine on my duck boat and let it sit. I don't run it dry, as I don't want to chance the floats or anything being out of whack from trailering on these rough MI roads.

[JohnsonM50]

Probably the water that is in todays fuels. You might also have some cheap gas in your area, who knows. But no, it is not normal around here. I simply dissconnect the fuel line from the engine on my duck boat and let it sit. I don't run it dry, as I don't want to chance the floats or anything being out of whack from trailering on these rough MI roads.
If theres water in the fuel from the ethanol it could be but avgas 100 LL has no E & it goes bad just as fast. Thats why I think too much air is in the flaot bowl that actually holds very little gas. Letting a float flop around in an empty bowl on ruff roads is a thought to remember as Jersey has alot of bumpy roads too & I always trailer.

[JohnsonM50]

Add some Stabil to the fuel, can't hurt can help like chicken soup. Are you using a E based fuel, no good? Not sure about the venting causing thre issue. Is there any evidence of water in the fuel when you clean out the bowl? No water, I drain it in a clean contaier to look. Stabile would do it tho.

[JohnsonM50]

M50
Just disconnect fuel line and run carb. dry before you take it out of the water. never put an outboard up with fuel in the carb. For storage I'd do that but from weekend to weekend it should be ok.

[JohnsonM50]

Thanks for the replies. Just seems odd that the stock single barrel can sit a month & start right up. Why I'm thinking air to fuel volumes inside the chamber.

[Fastjeff57]

..."never put an outboard up with fuel in the carb"

Right! I warn everyone to do this... or else.

Here's what ethanol gas and moisture form in the bottom of a carb (or tank) it allowed to sit a while. That "white gook" will not burn, it goes right thorough filters, and can NOT be made to burn with any known additive.

Jeff

[JohnsonM50]

..."never put an outboard up with fuel in the carb"

Right! I warn everyone to do this... or else.

Here's what ethanol gas and moisture form in the bottom of a carb (or tank) it allowed to sit a while. That "white gook" will not burn, it goes right thorough filters, and can NOT be made to burn with any known additive.

Jeff

While I realize this to be true, Im talking a week, not a month or more. Av gas has no ethanol & is known to last longer.

[Fastjeff57]

Only way to go!

Jeff

PS: Gas stations in Philadelphia are selling 15 % Evil-nol now. Dammed if I'll buy any.

[Ron Saxvik]

What are you using for intake manifold ? Looks very interesting !

[JohnsonM50]

What are you using for intake manifold ? Looks very interesting ! being unsure if it would work at all I kept it simple, its a stock manifold at the crankcase, milled down to expose the inside. I made a plate to cover it & mount the carb to. Theres a divider inside to separate the barrels/cylenders so ech cyl is fed by the adjacent barrel.
http://i35.photobucket.com/albums/d151/mes355/DSCN0389.jpg (http://s35.photobucket.com/user/mes355/media/DSCN0389.jpg.html)
the plate is epoxied on & the mount screws go thru both plate & manifold. The carb mounts to studs threaded into the plate theres no concern for in coming apart this way. Now that I know it will work a better manifold is in mind as well as some way to improve the reeds.

[zul8tr]

Only way to go!

Jeff

PS: Gas stations in Philadelphia are selling 15 % Evil-nol now. Dammed if I'll buy any.

Here in Fla State Legislature recently passed a law that fuel stations can cary E Free as they desire. It will take awhile but more stations will add an E free pump. Presently there are a few stations that offer it even before the new law. Hope other states follow Fla?

[Fastjeff57]

..."Here in Fla State Legislature recently passed a law that fuel stations can cary E Free as they desire."

Great! Those stations need to be patronized faithfully, while ignoring the rest. It's the only way WE the people can beat this ethanol crap.

Jeff

[chris3298]

you can look up ethanol free gas stations and that will give you a list in your state or nearest to your town that sell ethanol free gas. I sure hope i can continue to get it because if not i may looked into that aviation 100LL although not sure i could run it in my Tohatsu 50 TLDI when it comes down to never being able to get ethanol free gas i guess it will be searching out the 2 strokes to be my primary fishing motor.

[Ron Saxvik]

Thanks for sharing this........looks like a good winter project.

[omcstratos]

E free is readily available here in SC but it's usually only offered as 89octane, not 93 :mad: