Changing Compression fuel pump to electric

[fishamingo]

I have a 60 HP 2 cycle suzuki DT 60 engine in a 20 year old jet boat. Have been through engine and everything checks out with specs in manual. Runs great but only obtains about 4600 rpm at WOT and runs about 28 max mph WOT. Manual says should do 35 mph and 5200 RPM WOT. All jet drive components new and tweaked. Read in a forum somewhere that a guy changed out the compression powered fuel pump to electric and it solved his same problem. manual say 2 to 3 kg-square cm discharge pressure for pump. relates to about 42 psi which I have never heard of in a fuel pump. Most are 6 or 7 psi. Any ideas? Needs to have at least 15.85 gph discharge at WOT.

Thanks

 

[JB]

Re: Changing Compression fuel pump to electric

There isn't any reason that I can see that a pulse driven fuel pump in good shape would cause your problem.

What have you done to test the fuel pump? I take it that the engine is a 1990 model. Have you overhauled the fuel pump?

The pressure and volume numbers you quote are out of sight for a DT60. Are you sure they are for the fuel pump??

Whatever. A high volume electric fuel pump will not solve your problem and might give you more problems.

Check your bottom and the rigging. Don't know much about jet boats, but if you were prop driven I would say you are overpropped.

 

[ondarvr]

Re: Changing Compression fuel pump to electric

I have a 60 HP 2 cycle suzuki DT 60 engine in a 20 year old jet boat. Have been through engine and everything checks out with specs in manual. Runs great but only obtains about 4600 rpm at WOT and runs about 28 max mph WOT. Manual says should do 35 mph and 5200 RPM WOT. All jet drive components new and tweaked. Read in a forum somewhere that a guy changed out the compression powered fuel pump to electric and it solved his same problem. manual say 2 to 3 kg-square cm discharge pressure for pump. relates to about 42 psi which I have never heard of in a fuel pump. Most are 6 or 7 psi. Any ideas? Needs to have at least 15.85 gph discharge at WOT.

Thanks

You make it sound as if the boat and motor are a packaged combo, but also as if they are separate, which is it?

There can be many reasons for it to run slow, maybe its old and tired, the hull may be warped, the foam in the hull may be waterlogged, poor state of tune.

You say the pump has been tweaked, explain. Changing things within the pump can easily reduce the performance.

Do you live at a high altitude?

The fuel pump is not the issue, or at least not at the top of the list of possibilities.

 

[fishamingo]

Re: Changing Compression fuel pump to electric

Thanx. The fuel pump is new OEM. All JET DRIVE components, i.e. impeller, wear ring , distance washer has been checked for specs but washer forward of impeller had wear so changed to specs (tweaked).

None of the things mentioned are the cause. Engine compression is better than specs and each cylinder is within 5 % of each other which is great. Can't believe age of engine would come into play if everything meets specs and has either been replaced or double checked.

 

[fishamingo]

Re: Changing Compression fuel pump to electric

Boat and engine packaged together new. Pump is new OEM but did not check preassure or flow since it was new. Otherwise everything in boat checks out. When I bought the boat I expected once restored to get about 30 MPH but what bothers me is the low RPM at WOT. Could be warping of hull but not visible, The engine after remounting seems to be a minute fraction off the aft to forward center line. Everytime I have tried re aligning engine with hull it checks OK but after I run it, it moves back just a fraction. Never thiught about that being the problem but could be. May try moving the engine back to center line, shim the thrust plate against the fiberglass to exact center, then retighten mounting bolts with shims in place. I guess with the enging pushing the boat less than one degree sideways could cause a loss of speed but unsure about RPM. Thanx for the reply.

 

[99yam40]

Re: Changing Compression fuel pump to electric

Is this a outboard motor with a jet drive on it?
If compression and spark is good then look at the timing and then it is to the fuel/air ratio.
to develop HP the carbs are the ones that feed proper amount of fuel to the volume of air flowing through it. If their jets and passages are clean, then maybe the exhaust is not allowing enough flow out.
The motor has to breath properly to develop the power it was designed to

 

[fishamingo]

Re: Changing Compression fuel pump to electric

Thanx LT

'tis a 12.5 jet boat designed for skiing and has a 60 DT Suzuki engine sitting behind the seat. Never really thought about the exhaust not producing, good thought. In High school we used to stick potatoes in guys (the ones we didn't like) cars exhaust pipes. Took 'em ever to find out why their 52 Chevy wouldn't run. Great observance and I will check that ..................uh! Just how would one check the output of an exhaust?

 

[99yam40]

Re: Changing Compression fuel pump to electric

Not sure how to test. but on outboards we de-carbon from time to time to make sure everything is removed by running Seafoam or some other product. May have to open up the motor to see if too much carbon in exhaust ports and channels. Found 2 stk weed eaters that would not run because of the carbon in exhaust port, it was just a thought.
May need to look in a different forum since it is not a outboard.