Force 125 fuel delivery ?

[redstrat]

After toying with this all summer I'm stuck. I now have 10 hours on my rebuilt (ported ) 125. It starts and idles beautifully. I can cruise at 3500 to 4200rpms all day and never misses a beat. But, if I throw the throttle down hard it will run like a bear for about 30 seconds and then die. I then have to re-prime to bring the fuel back up. I first thought it was the cap on the tank not properly venting. I replaced it with an older cap and saw some improvement. I then decided to swap out the 5/16" line for 3/8". This helped even more but I still can't run WOT without it stalling. I replaced the fuel pump diaphragm when I rebuilt it. Could it be that porting it has effected the operation of the pump or that it can't keep up with the demand of the motor the way I have it set up. I'm posting pictures so you guys can see what I have. I would love to figure this out before I put her away for the winter. Any suggestions are appreciated. P.S. Am I running a risk of damaging the motor by pushing it to the stall point?

 

[Frank Acampora]

Porting too aggressively can affect the crankcase pressure and thus fuel pump efficiency. You can try adding another fuel pump above the existing one like on the Chrysler 140 and Force 150.. Plumb it is series with the existing one. Output from the existing pump should feed the input of the second pump and output of the second should go to carbs. You will need another bypass cover with the fuel pump mount and you will need to drill the top bypass cover to accept a pressure fitting and hose for the second stage of the fuel pump. There should be room behind the electronics board. If not, space it out a bit.

 

[redstrat]

Thanks Frank, I should have all the parts to accomplish this. I may ask a few more questions when I get to it. Fingers crossed. I remember reading somewhere that an electric fuel pump is not advisable for these motors. What is your take on that?

 

[jerryjerry05]

The electric pump if it's a marine pump would work.
I don't like them cause they can keep pumping and fill the boat with gas after the motors off.
Like adding a bomb to your boat.
Maybe a check valve is not right?
What's the comp on that cylinder?Or all cylinders?
The connection on your tank where it comes out of the tank.
Change to an OMC or even a Yamaha fitting.
The Force/Chrysler ones were famous for sucking air.
The squeezie? Is it collapsing? There is a check valve in the ball. Possible it's bad.
Even new right out of the box they can be bad.

 

[redstrat]

No Title

Thanks Jerry, All the connection are clamped on barbed fittings. I've tried two different primer bulbs. The compression is 150lbs on all cylinders. I'm wondering if possibly the new diaphragm in the fuel pump is weak. I did port the motor but I think I was fairly conservative and I'm sure I didn't cut toward the crank altering the timing. I'm have a blast with this boat. I just have to fix this kink in the works.

 

[pnwboat]

If you suspect a problem with the fuel pump after replacing the diaphragm, I would suspect a possible sticky check valve in the pump itself. There are 3 check valves. Two of them are easy to get out. One of them can be a bear as it is pressed into place and no easy way to pull it out. You basically have to destroy it to get it out.

On a side note.....I have a ported 120HP motor that originally had the older figure 8 shaped pump. I replaced it with the newer square style Mercury pump. I don't know if the square style delivers more fuel, but I've never had an issue with fuel delivery.....even at WOT 6000 RPMs. Had to replace the By-Pass cover with one from a later model motor that had the correct mounting bosses and port for the newer style fuel pump. The main reason I went to the newer style pump was the diaphragm kit was about half the price, and it includes replacement check valves.

Forgot to mention that I have 5/16 fuel line from the built in 20 gallon tank through a water/fuel separator and a see through inline filter between the pump and carbs.

 

[redstrat]

Thanks pnwboat, I think I'll pull the pump apart and see if anything looks suspicious. All good comments as usual from my internet Chrysler/Force Bros.

 

[redstrat]

I decided to take a look at the fuel pump section of my Force service manual. I spotted something I had not noticed before. The fuel tank should be no lower then 24" below the fuel pump. The bottom of mine is about 31" and I'm hoping to raise the motor a bit more. I think I can raise the tank about 5". Also, it doesn't look like I have room to run two pumps without a lot of modification. Electric fuel pump?

 

[Jiggz]

In addition to reducing the fuel pump "head", I also recommend by-passing the water separator filter to see if this will resolve your problem. If it does, then you might want to re-position the separator a little closer to the fuel pump or to the fuel tank.

 

[redstrat]

Man do I feel stupid. 58 years old with a masters degree and after pulling the tank out of my boat I have realized that I plumbed the water separator backward.:embarassed: The weather looks good this weekend. I'll let you all know how I make out.

 

[Jiggz]

Trust me, you're not the only one nor will it be your first. There are people on this forum who are also PHD'S (People High on Dope) and do the same! Lol

 

[redstrat]

PHD'S (People High on Dope) and do the same!

Thanks Jiggz, In my case the effects are only residual. :rockon:

 

[jerryjerry05]

I had a spare tank under the console on my other 21.
It had 12-13ft of 1/4in hose.It wasn't a problem for the pumps on my motors
The smaller diameter hose would be easier to draw through than a bigger hose.
Check the pickup tube for junk? Some tanks have a filter on the end of the tube???

 

[Jiggz]

24" vertical clearance is what was mentioned to be ideal which is totally different from horizontal distance.

 

[Steverino74]

Any chance the float level in the carbs is wrong - not allowing enough fuel into the bowl? Or maybe the floats having a leak?

 

[redstrat]

No Title

All is well. Reverse plumbing the water separator is definitely a NO NO. Went out yesterday and she ran like a rocket and never talked back. Here are a couple of pics just for fun. Now I can put her away for the season and not obsess over it all winter. Thanks everyone for your input. You guys are great. I'm looking for a buy on another Force with Chrysler style hood for the 15' 1973 Hustler tunnel boat I picked up for my next build. Jim Umbarger built and raced these boats back in the 60's with Chizzler power. :joyous:

 

[redstrat]

No Title

All is well. Yesterday we got back out on the river and she ran like a rocket and never talked back. I guess we learned that plumbing the water separator in reverse is a definite NO NO. Thanks to everyone for your help. I'll be on the lookout for good buy on another Force with a Chrysler style hood for my next build, a 15' Hustler tunnel boat. Jim Umbarger built and raced these boats back in the 60's. Here are some pics, just for fun.

 

[redstrat]

No Title

All is well. We got out on the river yesterday and she ran like a rocket and didn't talk back. I guess we learned that plumbing the water separator backward is a big No No. Thanks to all that replied. You guys are the best. I'm keeping my eye out for a deal on an older Force with the Chrysler style hood for my next project, a 1973 15' Hustler tunnel. Jim Umbarger built and raced these boats back in the 60's with Chizzlers for power. Here are a couple of pics just for fun.

 

[albz419]

After toying with this all summer I'm stuck. I now have 10 hours on my rebuilt (ported ) 125. It starts and idles beautifully. I can cruise at 3500 to 4200rpms all day and never misses a beat. But, if I throw the throttle down hard it will run like a bear for about 30 seconds and then die. I then have to re-prime to bring the fuel back up. I first thought it was the cap on the tank not properly venting. I replaced it with an older cap and saw some improvement. I then decided to swap out the 5/16" line for 3/8". This helped even more but I still can't run WOT without it stalling. I replaced the fuel pump diaphragm when I rebuilt it. Could it be that porting it has effected the operation of the pump or that it can't keep up with the demand of the motor the way I have it set up. I'm posting pictures so you guys can see what I have. I would love to figure this out before I put her away for the winter. Any suggestions are appreciated. P.S. Am I running a risk of damaging the motor by pushing it to the stall point?

After toying with this all summer I'm stuck. I now have 10 hours on my rebuilt (ported ) 125. It starts and idles beautifully. I can cruise at 3500 to 4200rpms all day and never misses a beat. But, if I throw the throttle down hard it will run like a bear for about 30 seconds and then die. I then have to re-prime to bring the fuel back up. I first thought it was the cap on the tank not properly venting. I replaced it with an older cap and saw some improvement. I then decided to swap out the 5/16" line for 3/8". This helped even more but I still can't run WOT without it stalling. I replaced the fuel pump diaphragm when I rebuilt it. Could it be that porting it has effected the operation of the pump or that it can't keep up with the demand of the motor the way I have it set up. I'm posting pictures so you guys can see what I have. I would love to figure this out before I put her away for the winter. Any suggestions are appreciated. P.S. Am I running a risk of damaging the motor by pushing it to can anyone ple

After toying with this all summer I'm stuck. I now have 10 hours on my rebuilt (ported ) 125. It starts and idles beautifully. I can cruise at 3500 to 4200rpms all day and never misses a beat. But, if I throw the throttle down hard it will run like a bear for about 30 seconds and then die. I then have to re-prime to bring the fuel back up. I first thought it was the cap on the tank not properly venting. I replaced it with an older cap and saw some improvement. I then decided to swap out the 5/16" line for 3/8". This helped even more but I still can't run WOT without it stalling. I replaced the fuel pump diaphragm when I rebuilt it. Could it be that porting it has effected the operation of the pump or that it can't keep up with the demand of the motor the way I have it set up. I'm posting pictures so you guys can see what I have. I would love to figure this out before I put her away for the winter. Any suggestions are appreciated. P.S. Am I running a risk of damaging the motor by pushing it to the stall point?

Can someone tell me if thats the main fuel hose coming from the gas tank going into the pump where the arrow is pointing in and says filter???? Please anyone

 

[puffitu]

Old and tired thread-start a new maybe??