40hp OMC mpg

[sparks4540]

Can anyone tell me what the Miles Per Gallon may be for my boat. 16ft open deck Starcraft with a '91 OMC 40hp 2-stroke outboard. I was figuring around 7-8. I have not had this combination on the water yet.

Thanks,
Chris

 

[mthieme]

Re: 40hp OMC mpg

MPG ??!??@????
If you keep the tires inflated properly, you're in the neighborhood.

My 35 burns about 3 GPH at WOT if that helps.

 

[kenmyfam]

Re: 40hp OMC mpg

Can anyone tell me what the Miles Per Gallon may be for my boat. 16ft open deck Starcraft with a '91 OMC 40hp 2-stroke outboard. I was figuring around 7-8. I have not had this combination on the water yet.

Thanks,
Chris

Approximately 4 gallons per hour at WOT. Significantly less at cruising RPM.
MPG is not really a good rule of thumb though. Currents, load in your boat and set up will play a large part in how much fuel you will use.

 

[steelespike]

Re: 40hp OMC mpg

If you get yourself a tiny tach and work on your setup.Raise the motor 1/4" at a time by laying sticks on the top of the transom.Raise it to a point just before venting(cavitation) becomes a problem.Be sure it has a good grip and pumps water.In ideal conditions you could gain a couple of mph and a slight improvement in efficient use of your GPH.

 

[sparks4540]

Re: 40hp OMC mpg

Thanks for all the replies. What is a good cruising RPM for this motor and the maximum it should run at WOT? I am going to invest in a tach, however I have read some interesting things about them. Some of the tachs have issues displaying the proper rpm at low or high rpm, above 4500. Has anyone else heard of this and could recommend a quality tach. I read an OMC gauge would work best??? Thanks again.

 

[steelespike]

Re: 40hp OMC mpg

It does make sense that an OMC tach is probably best.
I believe quite a few here have gotten the Tiny Tach and had good luck with it.Just be sure you tell them what you have.
You'll have to experiment to find the best cruising rpm.it could be anywhere from just on plane to about 2,000 rpm higher.test trials or a flow meter is about the only way to figure it.As far as the ,max rpm I don't know the exact but you would surely be within limits at 5,500.

 

[Silvertip]

Re: 40hp OMC mpg

Your information on tachometers is not accurate at all. Any current Teleflex or Faria tach for a two stroke motor will work just fine and can be relied on to provide meaningful RPM data. The wide open throttle rpm for this engine is 4500 - 5500 rpm and the closer to 5500 you get the better. As was pointed out, MPG on a boat, just like in a car, depends on how fast you run, the size of the boat, the load, water conditions, whether the engine is in good condition and has the proper prop for the load. Assuming everything is up to snuff, at wide open throttle with an average load that engine will consume roughly 4 gallons of fuel per hour. At 3500 RPM it will be roughtly 2.5 - 3 gallons/hour.

 

[sparks4540]

Re: 40hp OMC mpg

Thanks for all the info. The tach issue that I see is that all the tachs I have looked at, ie.Faria., are for outboards with alternators. My 40 does not have charging capabilities. Would this matter or can I still use any tach?

 

[tashasdaddy]

Re: 40hp OMC mpg

then you need a tiny tach, it reads off the spark plug wire. i have a tiny tach, i used it to get my motors set up, then put it in storage. once you are properly set up, you really do not need a tach. you have to order the correct one for your motor, also the length of the wires you want.

 

[sparks4540]

Re: 40hp OMC mpg

I read the tiny tach is digital and updates every 2 seconds or so. I have always used an analog gauge. Is there any analog gauge out there that will work for me? Thanks again.

 

[tashasdaddy]

Re: 40hp OMC mpg

you can use a timing light with the tach feature, it connects to the battery, and the pick goes to the #1 spark plug wire.

 

[Silvertip]

Re: 40hp OMC mpg

Is your engine a rope start or electric start. If it's electric start it should have a charging system. If it's a rope start, I would suggest you try an automotive tach that can be set for a 4-cylinder engine. Those tachs pick their signal from the ignition coil. If you connect that tach sense wire to the primary side of the ignition coil, it should read correctly PROVIDED the tach can recognize the pulse. A two stroke engine fires a cylinder one every revolution of the engine whereas a four stroke fires every other revolution. Therefore, a two cylinder two stroke would deliver the same number of pulses as a four cylinder four stroke auto engine where the engine uses a single coil.

 

[sparks4540]

Re: 40hp OMC mpg

The engine is a pull start. Based on the last response, I should be able to utilize a standard analog tach and set the cylinder switch to 4. Correct?