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1999 force 40 hp surges at wot

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busa

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I have a 1999 force 40 hp on a 16 foot smoker craft. I bought the boat from original owner and he was unsure about the surge. The boat runs perfect at all speeds except WOT. At WOT it starts to surge. It is not terrible just want to get it corrected. I have replaced fuel lines, spark plugs, carb kit, primer bulb. I have tried squeezing primer bulb while running with no change. If a fuel pump is failing what are the signs? could it maybe float level? Its at the local shop now being looked at but they cant narrow it down either but they do acknowledge the surge as well. They think it is fuel related. they were taking it back out today with a remote gas tank and hose. Any help is much appreciated, Thank You
 
The float level could affect the wide open.
The fuel pump could also.
Does it have a tach? Try unhooking that and see if it helps.
outboardignitiondotcom has test procedures for the ignition on this motor.
 
i stopped by local boat mechanic today to check on boat they have had it 2 weeks. Make a long story short i pulled it home with same issue and a empty wallet. i will order a carb kit and fuel pump rebuild kit just to narrow it down more. It does not have a factory tack but i have put on a tiny tach trying to help figure it out
 
Is there a way to test the trigger with out pulling fly wheel on the 40 hp force. I just want to check each and every thing that could be causing the surge. Thanks for your help and input jerryjerry
 
Engine will not rev beyond 3000-4000 RPM:

  1. Connect an inductive Tachometer to each cylinder in turn and try to isolate the problem. A single cylinder dropping fire will likely be the switch box or ignition coil. All cylinders acting up usually indicate a bad stator.
  2. Connect a DVA meter between the stator’s Blue wire and Blue/White wires. Perform a running test. The DVA voltage should jump up to well over 200V and stabilize. A drop in voltage right before the problem occurs indicates a bad stator. (Blue to Engine GND if the engine has a Red stator kit installed).
  3. Connect a DVA meter between the stator’s Red wire and Red/White wires. The DVA voltage should show a smooth climb in voltage and remain high through the RPM range. A reading lower than what is on the Blue wire indicates a bad stator.


High Speed Miss:

  1. Connect an inductive Tachometer each cylinder in turn and try to isolate the problem. A high variance in RPM on one cylinder indicates a problem usually in the switch box or ignition coil. Occasionally a trigger will cause this same problem. Check the trigger as described above under “No fire or Intermittent on One Cylinder”.
  2. Perform a high-speed shutdown and read the spark plugs. Check for water. A crack in the block can cause a high speed miss when the water pressure gets high, but a normal shutdown will mask the problem.
  3. Remove the flywheel and check the triggering and charge coil flywheel magnets for cracks or broken magnets.

Your Tiny Tach can help diagnose the these.

They charged you and didn't fix it?? Call the BBB
 
Also!! if your getting spark the late model triggers don't usually fail.
That usually ends up being the pack, maybe the stator?

Fill out the profile, add a location.
You might be close to someone who can help???

You have a built in tank? or a portable?
The built in: the pickup tube can be getting debris in it and shutting the fuel flow off.
 
Thanks for the good info. I think i will pull the strainer first than move onto the carb and fuel pump kits. The gas line from the tank to the motor has a quick disconnect right before it goes into motor cowling. Is it a good idea to just run a new hose with out that quick disconnect? There is a good chance i would never disconnect there anyhow. I have read that they can sometimes suck air there if the o rings are bad. Is this a good or bad idea?
 
You want to be able to disconnect the fuel line and let the engine run out of fuel between uses to keep the carbs clean. Replace all the fuel lines in the motor when you rebuild the pump and carbs.
 
Some people do this, I don't think it's a good idea.
Running carbs dry.
Running the carbs out of fuel can cause scoring of the cyl. walls.
The top carb runs out of fuel first and causes the motor to stall.
It leaves some fuel in the bottom bowl anyway.

The inline connectors can go bad and allow air in and cause a problem.

He's already replaced the lines.

The pickup in the tank shouldn't have a strainer.
But might have gunk in the tank big enough to block the pickup.

Built in tank? Check the tank vent line.Bugs get in and make nests and block off the air.
 
Had a few minutes to work on boat today. I pulled strainer from built in tank and is was very clean no gunk on it at all. There is about 10 gallons of gas in tank think i will drain that and start with new gas. I think i will bypass the fuel line quick disconnect and just run a hose. If that seams to help i will get a new quick disconnect for it. I wont have the carb and fuel pump parts for a few days. After i get it back together and try it im thinking about getting some starter fluid and spraying around the base of carb and fuel pump while its running to check for air leaks. Is this a good idea.
 
Fact----Running fuel out of the carburetors is the best thing you can do to keep them clean------And on multiple carburetor engines there is plenty of oil on the parts to avoid any scoring !!
 
Ok had a chance to work on motor today, I took carb off and getting ready to put kit in it. While i had the carb of decided to pull reed valves to inspect them. Not sure what every thing is called but it has 16 thin flaps that move to let fuel/air thru. there is 4 banks with 4 flaps on each. 3 of the 4 banks are seated tight against the base and can not shine light thru them. But the 4th bank i can see light thru all 4. I measured the gaps the best i could starting at top .018 next .015 next .010 next .007. could this be a issue or is this ok. If it is a issue what do i need to do to fix it. I still will put carb kit and fuel pump kit in.
 
I have tried it with different tanks with same results. I pulled carb off this morning. When i bought the kit i got it for 1500 to 3000 ft elevation which has a .060 main jet. The jet that is in it is a .062 which i think is used from 0 to 1500 ft elevation. The lakes I fish are 2600 ft. Should i replace the main jet with the .060 or leave in the .062.
 
You can try a prop with less pitch also. Yes put in the smaller jet and keep and eye on the spark plugs. They should burn a noce toasty brown on the center electrode insulator. Keep the larger jet handy for running at lower elevations. It coud be you loading up rich on fuel a prop with less pitch may get it to open up?
 
Ok guys we got it done:cool:, I changed all the fuel lines, checked pickup screen, rebuilt fuel pump, cleaned carb put new gaskets, new main jet and needle . Bypassed the quick disconnect on fuel line, replaced fuel filter and put all new gas in it. I'm not sure what the one thing was that fixed it but i took it to the river this afternoon and it ran like a top 5500 RPM no miss or surge and picked up 2 MPH. I will order a new quick disconnect for the fuel line. One thing i did find that could have been the main problem was the 5/16 inch hose that goes from the block to the fuel pump. The fitting on the block was super loose like it was about ready to fall out. I replaced with new and got it tight. Any way all is good thanks for all the help with everthing. You guys all had great ideas and tips to help get me going , Thanks for every thing...
 
This goes along with the #20 post

One way to test: run the motor and get it up to operating temp( make sure the thermostat is still in the system) run it at wide open for 4-5 min.
Then turn the key off. Don't throttle down just turn the key off.
Then pull the plugs and check the condition of the burn.
 
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