Outboard Propane conversion?

[bljones]

At the risk of reinventing the wheel, I am exploring using a propane powered O/B as the auxiliary propulsion on the TardisCat. The conversion is relatively simple, and IMO has some distinct advantages.
1. Simplified fuel delivery. Seems like 98% of O/B problems can be traced to fuel delivery. Clogged jets, sticking floats, vapour locked tanks, and the problem is only getting worse with new fuel blends that are deadly to hoses and seals.
An existing carb can be converted to use propane and eliminate the jets, floats, etc.

2. One boat, one fuel. Right now on Whiskeyjack, we have an alcohol stove, a propane grill, a diesel inboard and a two-stroke gas outboard for the dinghy. Therefore, on a small boat with limited storage, I have dedicated/isolated/vented propane storage, dedicated/islolated/vented gasoline storage, dedicated alcohol storage, and a diesel tank. The idea of only needing a propane locker has appeal, especially from the I-don't-want-to-build-anymore-stuff-than-I-have-to point of view.
3. Better fuel control means better engine control. I like the idea of being able to have finer throttle response with an inline valve rather than a carb at the end of a cable linkage.

Propane is not as powerful as gasoline, so fuel consumption will be higher. Other than that, I am not sure I see any downside.
This is where you all come into play- what am I missing?

I've got a Chrysler Sailor 250 outboard to experiment with (thanks to the DonorBoat). If anyone is interested, I'll blog the process.

[WanderingStar]

Sounds interesting, keep us posted.

[-OvO-]

energy density, range, ease of refueling. Not that those are necessarily deal-breakers, but they are downsides.

[tommays]

Having run a stationary GM 4.3 V6 natural gas motor for well over 40,000 hours over the last 12 years or so i can assure you they still need carb service and have plenty of other issues

Now you can carry around a manometer because there so fussy about fuel pressure

[mxracer19]

As far as fuel longevity goes, propane doesnt hold a match to diesel

haha alright...joking aside, most Zambonis (ice resurfacer at rinks) are propane powered and I can tell you from experiance, propane tanks burn up FAST. From a single tank we might only get 3-4 hours of running time, although I'll admit that ice resurfacing places quite a strain on the motor.