OMC motor question? [Archive]

saxatilis

05-19-2000, 11:08 AM

My 1996 Johnson Ocean Runner 150 was bought two years ago at a significantly reduced price, because it was sitting around for a couple of years with gas in it. Since purchasing it I have had great luck with it, but my gas mileage really sucks. I have really paid attention to my throttle habits, with little improvement. A mechanic I met said that I should consider rebuilding the carbs. That sounded fine, until I found out that it has six. Is there anything else I can do? If I decide to rebuild the carbs is it something that I can do?

I would greatly appreciate your opinions.

tomdorazio

05-19-2000, 03:03 PM

Typical carburated 2 cycle motors are not very efficient. This is because some of the fuel air charge is used to clear the exhaust gas from the cylinder. My OMC 225HP used to burn about about 14 gals per hour at 85% throttle which is typical. This motor also has 6 cyclinders and 6 carbs.

You can buy an OMC carb rebuild kit which consists of floats check valve needles and seats and gaskets. The floats have a bendable tab which determines the gas level in the bowl and they must be properly set.

Generally the only reason for rebuilding carbs is that the floats are sinking or the check needles are leaking causing the gas level in the bowl to be too high. This may result in a rough idle hard to start flooded motor smooky conditon especially if more than one carb is in trouble besides poor fuel economy. A job like this is best left to a Professional Mechanic if you have no mechanical experience or an OMC shop manual.

If you acidentally lean out a cyclinder with this kind of set up you can easily burn a hole in the piston. Also if any contamination enters from the fuel pump it can eaisly lodge in the christmas tree carb fuel distribution header nipples causing one or multiple cyclinders to lean out. I use to remove and reinstall the whole fuel system every year from the internal fuel filter to the carbs and check the carbs as well to be sure that there was no contamination. I use to keep my boat at a mooring and once found sand and seaweed in the fuel pump and fuel system to the carbs. I guess it was spontaneously created in the gas after passing two fuel filters. An outboard bonnet lock stop that particual problem from every happening again.