poor performance & fuel consumption

[Mike W.]

I have a 1971 Chrysler 75 HP, 3 cylinder. The engine runs fine when I start it out of the water. When it is in gear on the water it will "miss" at high rpm and it will use 6 gal. of fuel in less than 15-20 minutes. Fuel will run out of the lower unit. The plugs are new. #3 cylinder plug does not get any carbon on it, It is wet with gas when I remove it. I have spark on all three cylinders. I noticed that it is putting alot of oil & fuel into the water. I removed the carbs and cleaned them. I did not put kits in them, however I didnt see any thing wrong w/ them. Could this be a fuel pump problem. Thanks

 

[scotiany]

Re: poor performance & fuel consumption

When you pump the fuel bulb , does it become and stay hard. If not, you could have a defective needle and seat valve in one or more of the carbs. Also, changing the fuel pump diaphragm couldn't hurt. If it were me , I'd rebuild the carbs with new kits. The Sierra kits come with good instructions. Another possibility would be a defective float(s) but I hope not. Get yourself a manual too. I like the Seloc manual .

 

[chry120]

Re: poor performance & fuel consumption

Mopar<br /> I just went through a similar up-hill battle. Just an idea, but is the main jet screw on the top(or near to it) of the carb set right? From what I have gathered most of them should be set at about a turn to one and a half turns out from lightly seated.

 

[Terry H]

Re: poor performance & fuel consumption

sounds like you have a needle/seat or float problem on #3. Fuel flooding that hole would act like that...just a Thought

 

[eurolarva]

Re: poor performance & fuel consumption

I would do a compression test on the motor. Cylinder three without carbon and good spark could mean a blown head gasket. If you cant do a compression test swap plug three with one of the other ones and see if plug three cleans up after running it. If it does I would look at the head gasket.