TOPIC: Carb Tuning '61 Starflite III 75 HP

My engine is equipped with what the repair manual refers to as the "1B" carb meaning it has adjustable low speed jets but fixed high speed jets. The engine consumes gas like my teenagers ate pizza. A 10 minute cruise around the lake at half throttle uses about a quarter of a 6 gallon tank of mid-range fuel. I had a 60 HP Gale with this carb on a much larger/heavier boat as a kid growing up and we could water ski for half a day on 6 gallons. The only peculiar behavior is the right hand (facing the engine) low speed jet doesn't affect low speed engine behavior whether I have it bottomed out or out 2 full turns. Adjusting the left hand jet in or out a half turn from optimal (about 1 1/4 turns out from seated) makes the engine stumble. Any ideas on why the right jet adjustment doesn't have an impact and could this be related to the abysmal fuel consumption? Any insights will be appreciated.

Doug

How fouled are the plugs. Does one carb feed two cylinders? If so it would be interesting to look at the plugs on the side that adjustment does not seem to change. I have this exact motor so I am interested is what you find out. Good luck.

The engines devour fuel. I'm afraid that your youthful memory of the Gale 60 fuel economy is pretty optimistic. I had a fully restored Gale 60 for about 10 years, and it drank gas like no tomorrow. Depending on speed and load, these 2 barrel OMC engines typically burn from 4 to 7 gallons per hour of run time. There is no way around it.

As for the low speed adjustment, my guess is that there is a little piece of "junk" lodged in one of the passageways of the carburetor. When the low speed air / fuel needles are working correctly, bottoming out one of the needles should kill the engine.

But seriously - these engines - and virtually ALL brands old 2 cycle engines 50 HP and higher consume a tremendous amount of fuel.

A tune-up is likely in order, and the magneto / distributor need to be checked to see that it is advancing correctly with the given throttle setting.

If the hull is holding water, or if bottom of the boat has any issues such as hooking, or fouling, it will GREATLY reduce fuel economy.

Turns out my problem was buggered threads at the base of the socket. Getting a tap to clean them up (1/4 X 40) was impossible. Finally, met a retired Marine field engineer who now does engine repairs and builds custom racing engines. Since I had a new needle valve to replace the old one, he took the old one and cut off the needle at the base of the threads then cut two grooves across the threads. Presto - custom tap. Ran it in and out three or four times and the new needle seats as it should. I asked him why none of the 10 or so other machinists I'd contacted thought of that. His response, "They're not ex-Marines." Sweet! While I'm not either, I hope I can be allowed this one Semper Fi!!!

Hoo-Rah! Now that you've got your idle problem straightened-out, it's time to address the gas-guzzling issue.

As Bruce said, the old 2-bbl V4's are thirsty devils! The best way to reduce the horrendous fuel consumption is to make sure the carb/distributor linkage is properly synchronized, and then to operate the engine at the optimum throttle setting for improved fuel consumption.

If found this video to be an excellent D-I-Y for the synchronization part:

www.how-to-diy.org/MvQIDFiXdr4XUw/How-to-synchronize-a-1960-75hp-V4-Johnson-Sea-horse-outboard.html

Once you have yours set up perfectly, the best way to keep some of the fuel in the tank is to cruise with the distributor fully advanced, but no further throttle.

As you'll notice in the video, when the carb/dist linkage is advanced to where the distributor hits the timing stop, the carb butterflies haven't opened a lot. Only when you advance the throttle beyond this point, does the secondary linkage/cam pick up and open the butterflies fully.

I don't know if you've ever looked down the carb throats on one of these when it's wide open, but you'll be horrified at how much gas is spraying into the carb!

A lot less at the lower throttle setting, with max distributor advance. A cruising speed at that throttle setting (or less if your hull allows) should be the best mpg for your setup.

Merc had a similar design feature on their old distributor-fired models, called the "economizer" collar. With the spring-loaded collar, the distributor could be rotated to hit the "spark advance" stop for max timing, with the carbs at a lower throttle opening. Further rotation of the linkage would open the carbs up fully for max power (and max gas-guzzling!).

Prop selection makes a big difference, too, even on these old Beasts. If the prop is too big, the engine will be overloaded and use even more fuel. Check full throttle rpm by tach, with just the driver in the boat.

If you have a battery-ign distributor, an automotive tach set on 8-cyl will work.

Tachs are pretty scarce for mag models. A portable tach such as "Tiny Tach" might do the trick.

HTH.......ed

X2 what Ed said. If you push it WOT and then back it off 200-300 rpm,it helps on gas consumption. On my 16' boat with it backed off 2-300 rpm the boat still runs around 31 mph. If this is the gentleman running the v-4 on the g3,you should be able to back off your throttle considerably and maintain good speed with that rig. Great combo.