I have a 1984 Frontier 25 with Whaler Drive rigged with twin Yamaha 200-HP HPDI engines. There are twin fuel tanks. They are currently each rigged to their own engine through their own valve, and fuel-water separating filter.
Is it possible to route both engines from the same fuel tank, [and use one fuel tank as a main] and the other tand as a] reserve?
I'm worried about fuel flow. I can't find [data about the fuel flow rate of a Yamaha 200-HP HPDI engine] anywhere.
1985 FRONTIER 25 Fuel Tank Rigging for Twin Engines
Re: 1985 FRONTIER 25 Fuel Tank Rigging for Twin Engines
I don't see any impediment to changing the fuel tank hoses, filters, and valves to create an option to run both engines from either tank. The only concern is for the portion of the fuel system that will be in common for both engines: you must use hoses and fittings large enough for the combined fuel flow of the two engines. Typically if you use fuel hose and fittings with 3/8-inch inside diameter you will be fine.
The fuel flow rate of any engine depends upon the throttle setting. At full throttle, you can figure that a modern outboard engine will consume fuel at a rate of (HP/11)-gallons-per-hour. For a 200-HP modern engine, that means the maximum fuel flow rate would be about 200/11 = 18-gallons-per-hour. To find data about a particular engine, look for a published performance test from the manufacturer for that engine.
Fuel consumption at lower horsepower will be generally proportional to horsepower by that same estimate. You can usually find those fuel flow rates in published test data, too.
The overall or average fuel consumption rate will depend entirely on how you operate the boat. Most boaters over-estimate the amount of time the operate their outboard engine at full throttle. Usually only a very small percentage of total operating time, less than five-percent, is spent at maximum throttle.
As for locating a performance test for a Yamaha HDPI engine, I found one with a GOOGLE search. The search arguments were "Yahama hpdi 200 performance test" (no quotes). That search led me to an archive of performance report from Yamaha. Here are a few for the VZ200 model:
http://yamahaoutboards.com/sites/defaul ... -CSK-A.pdf
http://yamahaoutboards.com/sites/defaul ... -G3B-B.pdf
http://yamahaoutboards.com/sites/defaul ... -MAV-C.pdf
http://yamahaoutboards.com/sites/defaul ... -RNG-C.pdf
The fuel flow rate of any engine depends upon the throttle setting. At full throttle, you can figure that a modern outboard engine will consume fuel at a rate of (HP/11)-gallons-per-hour. For a 200-HP modern engine, that means the maximum fuel flow rate would be about 200/11 = 18-gallons-per-hour. To find data about a particular engine, look for a published performance test from the manufacturer for that engine.
Fuel consumption at lower horsepower will be generally proportional to horsepower by that same estimate. You can usually find those fuel flow rates in published test data, too.
The overall or average fuel consumption rate will depend entirely on how you operate the boat. Most boaters over-estimate the amount of time the operate their outboard engine at full throttle. Usually only a very small percentage of total operating time, less than five-percent, is spent at maximum throttle.
As for locating a performance test for a Yamaha HDPI engine, I found one with a GOOGLE search. The search arguments were "Yahama hpdi 200 performance test" (no quotes). That search led me to an archive of performance report from Yamaha. Here are a few for the VZ200 model:
http://yamahaoutboards.com/sites/defaul ... -CSK-A.pdf
http://yamahaoutboards.com/sites/defaul ... -G3B-B.pdf
http://yamahaoutboards.com/sites/defaul ... -MAV-C.pdf
http://yamahaoutboards.com/sites/defaul ... -RNG-C.pdf