re jet for high altitude 1969 v4 115hp

[adam98]

1969 v4 115 johnson on bass boat

can you point me in the right direction? i would like to take my bass boat from 3000ft Im at now to 7000-8500ft.

I know we used to put Propylene oxide in our race dirtbikes and they would run with same jettting at 3000ft when we where at 8000ft and power was really good.not saying thats the best answer but that was an easy fix. for a day trip to high altitude

what would i need to do to rejet my carbs?

 

[fishrdan]

Re: re jet for high altitude 1969 v4 115hp

For a day trip, it's best to swap to a prop with less pitch and leave everything else as-is. 3 - 4" or less pitch would be my SWAG.

Never heard of propylene oxide, looked it up, seems pretty expensive for a 115HP outboard that will burn a LOT of fuel... You could burn through as much of it, as a lower pitched prop costs. Once the $100 of PO is gone, it's gone, but you can use the prop over and over again.

 

[adam98]

Re: re jet for high altitude 1969 v4 115hp

Thanks. Even with a rejet that Makes sense... Less power less prop. So everyone doesn't think I will be fouling spark plugs and barly run at those altitude?

 

[fishrdan]

Re: re jet for high altitude 1969 v4 115hp

Probably not worth the effort to re-jet for a single day, lots of work going lean, then lots of going back rich. I lean out for a single day with my 140HP Mercruiser, but it only takes 15-30 minutes to swap the jets as I can "pop the top" off the carb, pretty easy. I've run OB's up at that altitude without re-jetting and they have run without fouling plugs, but they were doggy and I wasn't using them for trolling, only WOT use.

Hard to tell if you'll have a slug at that altitude as it's a different boat and outboard. Take all the extra junk out of the boat you don't "need".