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Originally Posted by 544lure  I hate to ask this. Overload. What will happen? used lots of fuel? will the engine overheat? Sorry guys. |
It has more to do with engine longevity than anything else but it could also affect mileage/efficiency depending on how you run the engine and how you load the boat. Longevity means that the more you overload the engine the greater your chances of catastrophic failure long before it should happen.
The first thing to do is to find out your manufacture recommended WOT RPM - loaded and unloaded. Loaded means in gear underway you see what the RPMs at WOT will top out at. You would hold it at WOT until the engine RPM (and usually boat speed) will go no higher. Unloaded means engine in neutral you peg the throttle and let the engine spin up and see what the RPMs top out at. Unless there is a major problem with your injector pump or oil is getting into the intake manifold spinning it up to maximum RPM in neutral will not hurt the engine. The injector is governed and will let the engine only spin so fast. Some people find it un-nerving to do it but don't worry. Just spin it up until the RPMs stop climbing and note what the top RPMs are then back it off.
The unloaded RPM is to check to see that things like the fuel system are working as they should and the govenor is set correctly. Checking the loaded max RPM checks for proper prop size but if you don't make it to the recommended max RPM (or a little more) it could also be a problem with a number of things like the turbo, fuel system, lack of compression etc.
You can read what one of the local Cummins gurus has to say about the subject here:
Seaboard Marine - Custom Marine Diesel Repower Specialists
I don't know how much you plan on using the boat in the upcoming month or so but here is what I would recommend. First get the floscan installed. Then check and see what loaded RPM you get with the current prop. If it is at least the manufactures recommend WOT RPM (higher is OK for now) then top off the fuel tank and use the boat some and get the floscan calibrated. Take some readings and get the fuel use and speed readings at every 200 RPMs at idle all the way to WOT. After you do that then start playing with the prop. If you are more than 200 RPMs below the recommended WOT RPM them I would change out the props before you go through running much fuel through the boat trying to calibrate the floscan. You can check the floscan readings and note them, change the props, and after checking the loaded WOT RPM to make sure you can make the correct RPM go through and check the floscan readings again and note them. Then go though the calibration for the floscan. If after calibrating the floscan you find that it is very much off then you still have the readings with your old prop and can calc out what they should have been had the floscan been correct in the first place. Doing thimgs this way you will not be running the boat any more than neccesary if your overpropped and your overloading the engine.
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