85HP fuel problem

[aladin_sane]

OK, the stats first. I have 120 psi compression in all three cylinders. I have synced and set all three carbs. Now the problem. When I start the boat, it starts and idles OK. I can hit the throttle and the boat takes off and runs fine for about twenty seconds. The boat then stalls and sputters to a stop. If my copilot sits in the stern and squeezes the bulb every 15 seconds everything runs fine, so I assume the problem is the fuel pump. I rebuilt the fuel pump, new gaskets and diaphragm. I didn't replace the check valves, but I did inspect them, and the open and seal as they should. After the rebuild, the results were exactly the same. I checked the fuel pick up and replaced the fuel line from the tank all the way to the fuel pump including the bulb. I checked the vent line and it is clear. So, what's next? I am thinking I have a problem with the impulse line. I have not checked it, but that is the next place I am looking. It appeared fine when I had the fuel pump off.



Anyone have the solution for this one?

 

[Jiggz]

Install a clear fuel filter between the fuel pump outlet and the carbs' inlet. Fram G2 from Walmart for less than $5 will do and even comes with hose clamps. Next, use an external tank for now and make sure the vent is cracked open. Do a test again. Make sure you prime the fuel system until the clear fuel filter is at least 1/2~3/4 full. Ran the motor with the cowl off so you can see the status of the clear fuel filter. With proper fuel delivery, it should stay at least 1/2 full. If it empties, with this set up it tells you the problem is either the primer bulb check valve getting stuck or the fuel pump is not delivering the proper amount of fuel. However, since priming the primer bulb before makes the engine ran normally the problem could be the fuel pump or the wrong size of fuel hoses.

If the clear filter stays at least 1/2 full with the engine running normally the the problem is with the fuel tank, vent line or pick up tube.

 

[jerryjerry05]

Any inline connector is the fuel lines?
They have a seal in them that goes bad and can suck air.

 

[aladin_sane]

The only connections in the line are at the fuel pick up, both sides of the bulb and at the fuel pump. I will double check the hose clamps at each of these positions. I will also get a fuel filter installed as directed and report back. Thanks for the replies guys.

 

[Psychosis]

Does the boat have the gray USCG ethanol resistant fuel line? If so you might want to verify it was installed correctly. If incorrect the plastic tube on the inside can get pushed in and crumpled up when pushed onto a fitting. This can impair the fuel flow and starve the motor when running at higher rpms. Don't run it that way much as it can go lean and burn a piston.

 

[aladin_sane]

Yes, I think that is the fuel line I installed. I will be taking it all apart and looking for any damage and then taking extra care to make sure none of the connections are sucking air.

 

[aladin_sane]

I spent quite a bit of time messing with the motor again today. I installed the fuel filter downstream of the fuel pump, I took the impulse line off the fuel pump and turned the engine over and got good pulses, so I felt that was not a problem. I looked at the connections at the fuel pump, both ends of the bulb and at the fuel pick up on the tank. I did find that the hose clamp on the tank side of the bulb may not have been as tight as it needed to be, As soon as it quites raining, I will get in the water and see if It's fixed.

 

[aladin_sane]

OK, here is the latest. There was some improvement. I was at WOT for a full minute before the engine stumbled. I shut it down and took the cover off so I could observe the fuel level in my new fuel filter. I had my wife drive while I monitored the engine, We ran wide open for another sixty seconds before if stumbled again. The level in the fuel filter did not drop, but a squeeze of the bulb did restore full rpms and power. When I squeezed the bulb, you could see additional fuel rush into the filter, but the level didn't reall change. So, all this makes me think this is a carbuerator problem, not a fuel line or pump problem. What do you experts think I look at next?

 

[Jiggz]

It's possible the carbs' floats are not set properly thus not opening wide enough to allow more fuel flow when needed especially at WOT. Or it could also be the fuel pump is sucking on some air thus not delivering the proper amount of fuel. Usually with a clear filter, when it gets full of fuel you can tell if the fuel pump is sucking air because there will be bubbles in the clear filter.

 

[aladin_sane]

I dont think it is sucking air. I didn't see any in the fuel filter I installed.

 

[Jiggz]

In that case, start cleaning the carbs inlet ports and also check the floats make sure they are freely moving. Just for a note usually with a properly working fuel system, the clear filter will eventually get full. To make sure it gets the fuel straight to the carbs, the clear filter should be located a little higher (thus closer to the pump) than the inlet connection of the carbs and make sure it is properly oriented, inlet and outlet connections of the clear filter. Avoid installing the clear filter so it is in a horizontal instead keep it vertical as much as possible with the outlet connection at the lower end.

 

[aladin_sane]

Mine is mounted just as pictured in the link and sync video.

 

[aladin_sane]

The more I think about it, the more I am thinking I may have a sticking float in one of the carbs. I guess I will be tearing them down tonight.

 

[Jiggz]

Very possible.

 

[aladin_sane]

OK, here is my report. I took off all three carbs. I found nothing wrong with #1 and #2, I was a little worried that I was wasting my time. I was very happy to find when I took the bowl off of #3, the float pin was half out of its mooring. This left the bowl hanging at an odd angle, and I hope that was the root cause of my problem. While I had all three carbs on the bench, I thought I would carefully set the air screws to 1 and 1/8th out. Again, I found trouble on #3. That screw was out at least two full turns. I am hoping the combination of those two problems with #3 carb could be what I have been chasing.

Thanks for the help guys. i will report back once I can get on the water.

 

[Jiggz]

Exactly what troubleshooting is all about . . . process of elimination. You just can't sit, think and assume what is wrong but more about looking and finding and eliminating possible causes. Congrats . . . I'm quite sure that is the main cause of your problem.

 

[aladin_sane]

The frustration continues. I took the boat to the river after work today. The boat fired right up, but was idling way to fast from my previous efforts to tune it with the #3 carb flooded. I backed the idle screw out all the way and it was still too fast, so I went to pop the ball linkage off the throttle connection, and I cracked it. So no further testing was possible this evening. I have plans for the rest of the weekend, so I will try and find a part tomorrow at lunch and hopefully get the boat back in the water on Monday.

 

[Jiggz]

After some troubleshooting it is always nice to do a drive test of the motor before heading into the open water. The ball link rod because of age is usually very fragile. I adjust this rod by just loosening both lock nuts on each end and turning the rod itself. Anyways, that is water over the bridge now.

 

[aladin_sane]

Tonights adventure was confined to an enclosed harbor off of the local river, so it was easy to get the boat back on the trailer,

 

[Jiggz]

I meant to say drive way test.Meaning on the muffs.