Thread subject: Whaler Central - Boston Whaler Boat Information and Photos :: 1987 Johnson 90 running lean
Posted by darrenmolder on 07/01/10 - 4:34 PM
#1
After purchasing my '87 Montauk on the coast and returning home in the mountains it is running lean enough to cough and stutter especially at low speed or idle. I am trying to diagnose and remedy the situation, preferably without taking it to a shop. I boat mainly around the 2,500 ft level and am wondering if the altitude hasn't leaned it out as the motor was recv'd by me in fairly good order. The Johnson owners manual doesn't cover any carb. adjustments so I am looking for a few tips I might try before buying a shop manual for it as I'm not sure of putting too much money into her yet. I'm thinking it could be as simple as an air/fuel mixture screw. Thanks, Darren
Posted by Barryg on 07/01/10 - 6:00 PM
#2
Darren it could be something simple like bad gas. The Ethanol bug is a serious problem for the outboard motor. My father in law had a 60 hp Johnson this week that was running rough. We put in some marine additive and high test gas . We ran it for a few minutes and the problem cleared up. Hope your problem is fixed as easy as ours was.BG
Posted by joninnj on 07/01/10 - 9:25 PM
#3
Barry make a good point, Could be a simple issue... Sounds like a fuel delivery problem. 2500 ft is not that high up to effect operation... I would check all of the fuel connections, starting at the tank and line for leaks and the vent is open etc... and make sure the fuel is getting to the carb past the fuel pump.
Run some Seafoam or BerryMans B12 through it. A higher concentration, like triple the dosage from a smaller tank if you have one (3 gal would be work) to start cleaning the carbs and system. This will only help with marginal blockages and grime. If you have a really fouled/gummed up carb it may need a rebuild...
Posted by Joe Kriz on 07/01/10 - 9:37 PM
#4
From what I remember for High Altitude Jets, they aren't changed unless you are operating above 6 or 7 thousand feet.
You seem to have other problems.
Where do you have 2,500 foot hills?
You don't list your location in your profile so I can't determine which hills you have... :-)
I live in the mountains... 8 thousand and 14 thousand foot mountains surround my area.... The valley floor where I live is 3 thousand feet.
I typically boat from sea level to 4 to 5 thousand feet without much problem. The boat is faster and runs better at sea level, but still runs OK at the upper levels.
Honestly, I am not trying to make a mountain out of a mole hill, but I can't resist.
Posted by darrenmolder on 07/02/10 - 3:07 PM
#5
Thanks for the info. it sounds like I need to examine my fuel system so that will be my first priority. To answer your question Joe I live in the North Idaho Panhandle roughly 50 miles south of the Canadian Border. Most all our lakes are glacial, with varying altitudes however the most pristene kokanee lakes are around 2,500 ft. elevation and over 1,000 ft. deep. Thanks, Darren
Posted by DWinter on 07/02/10 - 4:23 PM
#7
Ok Joe and Darren, you guys have made me jealous. I've never run boats in water that was clean enough to drink. Hopefully sometime I'll get the chance to test that sweetwater. I've been all over the world, but thanks to Uncle Sam, It's been a salt life for me.