'88 Force 50 fuel economy

[mneal]

I have recently purchased a 20' pontoon with a Force 50 on it. It is getting terrible fuel economy. Roughly it is burning 5 gallons of fuel for about 30 min run time at idle or a little above. I am used to I/O's that get better fuel economy than this. I have also noticed it appears to have unburned fuel coming out from behind it. Is the mixture to rich, how do I adjust it. This is my first two stroke so bear with me. I know there is a needle setting in the carb, is this where it needs to change? <br />Thanks in advance.<br />Mitch

 

[roscoe]

Re: '88 Force 50 fuel economy

You should be using about 6 gallons per hour at near wide open throttle. That sounds like something is amiss. Is it firing on all cylinders? Is there a fuel leak in the carb or fuel pump?

 

[mneal]

Re: '88 Force 50 fuel economy

I thought that was way off, thanks for the info. I will have to start looking for the problem. Any ideas where to start, could the carb be that poorly adjusted?

 

[roscoe]

Re: '88 Force 50 fuel economy

Personally I think it is more than a carb adjustment. I don't think it would be running if it was set that rich. <br /><br />Many motors will run with one or more cylinders not firing, particularly at low rpm. THis could be a plug or plug wire, a coil, low compression. Or you may have a fuel system problem-- leak in fuel line, leak in fuel pump which could pour fuel into the block and out the exhaust, leak into the cowl area and then dripping out into the water.<br /><br />I guess I would start by pumping up the gas hose bulb, and looking for a leak. <br /><br />Then check the plugs for spark, and then a compression check. If you have low compression on one cylinder, the gas will not be burned and will exit the exhaust. If you have low compression, you should do a very thorough decarb process on the engine. This may free up a stuck ring.<br /><br />What does the motor do if you try to open up the throttle?

 

[mneal]

Re: '88 Force 50 fuel economy

It is only a two cylinder, would it still be able to run if one of the cylinders were not firing? I can't open it up yet, the exhaust snout is missing and the propeller cavitates when I try to do much more than an idle. I will probably have to wait until I can get the exhaust snout to do the decarb process as well, right?

 

[rogerwa]

Re: '88 Force 50 fuel economy

I had a 21ft pontoon with an 87 force 50 on it. I can attest to the 6 gal/hr rate at wot. <br /><br />First you may have a float that is not seating correctly, thus allowing fuel to pump thorugh the bowl into the cyliders and then get pumped out through the exhaust. What are the condition of the plugs? In my Force I would always replace the plugs every two months or so. It always had a little more zip after replacing plugs.<br /><br />On your cavitation issue, are you sure your prop hub is not slipping? Unless the prop is halfway out of the water, it should not cavitate that soon. In fact, mine never cavitated at all.<br /><br />A slipping prop hub may also account for some of the poor mileage.

 

[mneal]

Re: '88 Force 50 fuel economy

Glad to hear that I should be getting better fuel economy. The plugs were just installed. I will have to check the float. You are making me wonder about the prop though. How can I tell if the hub is slipping, just put it in gear and turn it to see if it spins? Just a little background this boat has been sitting out of the water for two years as the owner went through a divorce. He bought it used and never even put it in the water. The registration that was on the boat was 97 so that may have been the last time it was ran.

 

[12Footer]

Re: '88 Force 50 fuel economy

I don't have anything to add, just want to put my vote in here ,and agree with what has allready been sugjested..... <br />It's a fuel pump diaphram with a hole in it (rebuild kit is cheap and job takes 20 minutes max), leaking fuel into the block.<br />These diaphrams hate modern alcohol-'enhanced' fuel blends. the manual even warns not to use such fuels..But these daze, that's all there is!<br /> Argh.<br /><br />And, spun out hub is more than likely causing the cavitation. This motor is hard on prop hubs, so get and keep a spare prop aboard,and 'run rotation".<br />Odd, but I own two of these motors and spun out the prop hub once, and it was my own stupidity....(See, they don't run real good in mud). but my brother couldn't keep a hub fromn spinning out on it when it was his. My guess was his helm style (hole-shots and such). Me, I just put-allong,thru the manatee idle zones.<br />And I'm thinking, a 'toon requires mucho torque, and it probably spun out the hub just getting from point A to B.<br /><br />Do you smell raw fuel? What is your top speed?<br /><br /> 'cause I'm getting around 3GPH at trollin-speed, and 5-6GPH at WOT.<br />BTW, don't expect to get more than 5GPH on that hull on a good day. They are built to tug the party along, as opposed to planing out and skooting.

 

[DJ]

Re: '88 Force 50 fuel economy

mneal,<br /><br />Ditto the others on the fuel economy estimates.<br /><br />Toons require gobs of torque. Find out what pitch the prop you currently have is. If it's a 15" or higher, I would go down to about an 11' or 12". This will not lug the engine.<br /><br />You also need to find the source of the fuel leak. If it's not obvious from the visual inspection, then it's probably a fuel pump or carb issue.

 

[rogerwa]

Re: '88 Force 50 fuel economy

The props for these only come in limited pitches as I remember. I got a lower pitch for my toon on E-bay for about $45. It was next to new but had been sitting around a while.<br /><br />With my toon, I was able to tow a tube with an adult in it and give a decent ride on the tube. If you have the larger tubes, 21"or above, you will be better than me. I had 19" tubes.<br /><br />AS I mentioned e-bay has lots of parts for these motors. Also the carbs and fuel pumps are very easy to rebuild.<br /><br />Also, make sure they are the right plugs. I beleive they are the champion L76v gapless plugs. These engine need a cooler plug as I understand it..<br /><br />Seeing that it has been sitting for a few years, tearing down the carb and rebuilding fuel pump, as well as replacing the impeller would be prudent to do anyway..