75hp is very slow

[scottmm73]

Hooked the hose back up and ran the engine and sure enough the filter after the pump would empty.

Did this occur at idle, what were the rpms?

Have you tried pumping the bulb while someone else throttled the motor. Your diagnosis tells us that the pump is not working correctly. Have you taken apart the pump and checked out the diaphragm (any tears or small holes)? Was the pump put back together properly?

 

[Jiggz]

Try Scottman's suggestion of pumping the primer while revving the engine or try elevating the tank at least the same height as the fuel pump while revving and see if things improve. This is just for troubleshooting just to see if things will change which would indicate the pump has a hard time pushing fuel because of the "head pressure" it has to overcome from the tank or primer bulb.

 

[bigbz28]

Yeah, I tried pumping the bulb while reving it and as long as I keep the filter full it runs fine. And Scottman, this happens at speeds above idle. But I can't help from wondering if the fuel is getting in somewhere else because the way it would stay reved up and not return to idle. Nothing is sticking or mechanically causing it, the throttle valves are still closed

 

[bigbz28]

And I did take the diaphragm out and shined a flash light through it and could not see any holes.

 

[scottmm73]

Well, fuel alone will not keep the motor running. It must be atomized and mixed with air(oxygen) to combust. However, we do know at higher than idle rpms the pump is not keeping up with the fuel demand. The high speed jets are fixed, correct? Or can you adjust them? If so, set all jets (low speed and high speed) to nominal and re-adjust. Are the carbs leaking fuel at all, when the motor is running (maybe not at idle, but could be at higher than idle rpms)? Have the check valves been replaced or could use replacement? Diaphragm has no holes but is it distorted? Could the fuel pump halves be warped, so that a vacuum is not achieved?

 

[Jiggz]

Yeah, I tried pumping the bulb while reving it and as long as I keep the filter full it runs fine. And Scottman, this happens at speeds above idle. But I can't help from wondering if the fuel is getting in somewhere else because the way it would stay reved up and not return to idle. Nothing is sticking or mechanically causing it, the throttle valves are still closed

When idle rpm stays up above 2000~3000 RPM does the cam stays in the idle position (mark it first then try again) which is indicated by the scribed line on the cam in relation to the slot on the eccentric screw? If it stays at normal idle position and the engine is still idling above 2,000~3000 that would mean fuel is being introduced somewhere other than through the carbs and this could only be from the fuel recirc system or a leaking fuel pump. But with the recirc system, the increase in rpm should only be temporary and should not last but a few seconds to clear the fuel puddle on the lower cylinder.

 

[bigbz28]

Yes the cam is at the idle position. My daughters birthday is this weekend and I promised her I would take her to the lake so until I figure it out I am going to get an electric fuel pump and see how that does.

 

[Jiggz]

Goodluck and enjoy.

 

[bigbz28]

Well, the electric pump made a slight improvement. What are the specs for the float heights? This time I was able to wide open throttle but again only for about 30 seconds. However, at first it wanted to hesitate as though not enough fuel even though the filter stays full now. After 30 seconds it starts to lose power and I can only go with the throttle control on "cruise"

 

[Jiggz]

With the bowl inverted, the floats should be horizontal or level with the casting of the carb. In upright position, you should be able to lift the bowl up to the horizontal level without touching the center post or any of the jets both in up and down position. Question, after 30 seconds with the electric fuel pump and the motor unable to go full throttle, what was the status of the clear fuel filter, was it still at least 3/4 full. If yes, then you might have a sticky float on one of the carbs. Some carbs have preloading spring to ensure the float comes down to open the needle port. Check and double check the floats are not binding or rubbing on anything and then try again.

 

[bigbz28]

Thats exactly what I thought LC Jiggz, basically a rule of thumb that on small engine carbs the float should be horizontal. The 1st time I looked at them they were right on and there was no dirt or blockage anywhere that I could see. When I was thinking the they were drawing in too much fuel that the pump couldn't keep up I adjusted them to close sooner but that still didn't help. Answer: YES! with the electric pump the filter stayed almost full the whole time. I tried to pump the primer just to see if that would help it run better as it did before but this time it made no change and was relatively hard to squeeze. Tomorrow I will take the carbs back off and correct the floats and double check everything, make sure there are no clogged jets.

 

[bigbz28]

Today I'm going to switch the top carb with the bottom one and take it to the lake and see what happens. Question: Should I have the same result and the top carb isn't getting enough fuel, what do you think about using both the electric fuel pump and the mechanical one together? Kind of like on some cars that have 2 pumps. One that delivers the gas to another pump which then feeds the engine. I'll probably take some extra hose with me just in case and see how it works

 

[bigbz28]

One more question... Was the update to this forum performed by the same people who created Healthcare.Gov?? It's having some serious issues

 

[Jiggz]

With the fuel filter staying full, we can rule out the fuel pump as source of the problem, even IF the same results happen, i.e. the top carb still starving of fuel. When you switch the carbs, take the time to inspect and thoroughly clean the top carb before re-installing. Blow compressed air into all ports and jets and validate the float operation is correct. Additionally, check the fuel hose connecting the mid carb to the top carb for any restrictions like lamination or debris.

 

[bigbz28]

Think I found the problem and finally end this thread! (at least until the next problem show up) Took apart the top carb again and tried to blow through in fuel inlet. Couldn't... not even with the needle removed. Unscrewed the needle seat and found it was clogged. Blew it out with compressed air and now it's free. Gonna still switch places with the bottom carb and test it out after work.

 

[Jiggz]

Thanks goodness we are finally seeing the light at the end of the tunnel! Remember, we still have the mechanical or original fuel pump to deal with. Unless, of course, you just decide to stay with the electric fuel pump. Let us know of your latest test run. Goodluck and enjoy again!

Note: Personally I would have just kept the top carb at its original position to make sure you have the problem localized especially now that you think you have found the problem. But then of course, that is just me.

 

[bigbz28]

Well, it ran 100% better last night. Only problem I had was that it doesn't seem to like the wake of other boats any slows down a bit when it gets that extra load. It didn't really do that before. Plus it only topped out at 25MPH, used to be 35. I haven't pulled the spark plugs yet but I think this could be some what caused by the carbon on #2. For right now, I'm just estatic for the fact that I now can cruise faster that 5MPH!! Thank you so much for your help!!!

 

[Jiggz]

After all those tinkering and tweaking to troubleshoot, you will need to re-tweak her again. First make sure she is trimmed properly. Wakes should not be considered added load unless she is plowing through the water (meaning she is trimmed in too much) instead wakes should make her rise through the water or wake if properly trimmed. Take note of her WOT rpm and speed, double check the link and synch make sure the throttles are in full horizontal with the control lever in full forward. Check the plugs and lastly timing.

 

[bigbz28]

Ordered another fuel pump diaphragm this morning. Gonna try it again just to see if that was the problem with the fuel delivery

 

[Jiggz]

I was just thinking about your situation with your WOT speed topping at 25 MPH. With the electric fuel pump it is really hard to see if it is capable of delivering the right amount of fuel at WOT unless you ran the motor at WOT with the cowl cover off. With an electric fuel pump, if it is slightly falling short on delivering fuel at WOT, it will actually limit your WOT speed since it will start to starve of fuel (not fully starved but reduced) with prolonged WOT speed. And if the cowl is on you can never tell since by the time you slowed down and stopped to check the clear fuel filter, it will be full again because the electric fuel pump operates at constant speed and delivery. Unlike, an attached fuel pump which increases delivery at higher speeds. It's just a thought that's maybe the reason your WOT speed tops 25MPH vice 35MPH as before.