Please help Figure this one out,your a hero

[jbeener1]

Re: Please help Figure this one out,your a hero

You do not check pressure on the fuel inlet side of the pump, you check the vacuum with an appropriate gauge to see if there is any restriction in the fuel system from the tank pickup to the pump inlet fitting. The vacuum reading should be less than 4" Hg with a healthy system showing less than 3"Hg. A good tech will also temporarily attach a clear hose to the inlet fitting of the pump to monitor for any incoming air bubbles which will give the exact symptoms that the original poster initially described in this thread. This was mentioned early in the thread and has not been done according to the person with the problem.

I have put a temporary clear line from the tank to the fuel pump and ran it with that on there while i had the vaccum gage hooked to the inlet side of the fuel pump,mine showed a 2 to possible 3 it was hard to see if it was going to a 3 while i was running WOT on the lake. Thanks for your help.

 

[nwcove]

Re: Please help Figure this one out,your a hero

so its working ok now??

 

[jbeener1]

Re: Please help Figure this one out,your a hero

so its working ok now??

NO sir it is not,i didnt get a chance to run it over the weekend,we've had to much rain. But i do have a question. Are there suppose to be any bubble in the fuel line between the fuel pump and the carb?? I have read there should be some and others say no bubbles at all. I keep thinking that it has something to do with the carb but i dont understand the where the bubbles come from if ive changed everything out from the tank to the fuel pump..

 

[jonjohnson]

Re: Please help Figure this one out,your a hero

NO sir it is not,i didnt get a chance to run it over the weekend,we've had to much rain. But i do have a question. Are there suppose to be any bubble in the fuel line between the fuel pump and the carb?? I have read there should be some and others say no bubbles at all. I keep thinking that it has something to do with the carb but i dont understand the where the bubbles come from if ive changed everything out from the tank to the fuel pump..

I am very new to this, but with what I have read, and spoken to outboard mechanics, it appears that you have a blockage in one of your high side jets, not the idle or mid range jets, since you can idle and cruise at a midrange speed. Also I used to rebuild my motorcycle carbs all the time, and the same thing applies there. Hope that helps or reiterates what others have said. I hope you find your problem. By the way, I have a similar if not the same problem, my 1974 70 hp, will go about 23 mph and stops accelerating at about 3/4 of the throttle/forward shifter, but does not kill the engine, just stops eccelerating. We have had alot of rain also, I'm preparing now to check my pulses per min. also. If I find my problem, I will report back, also if anyone has advice for me, I would also appreciate it, (not to hijack your thread or anything.)
I will also be checking my carbs again since that very well could be my culprit as well. Good luck.

 

[jbeener1]

Re: Please help Figure this one out,your a hero

I am very new to this, but with what I have read, and spoken to outboard mechanics, it appears that you have a blockage in one of your high side jets, not the idle or mid range jets, since you can idle and cruise at a midrange speed. Also I used to rebuild my motorcycle carbs all the time, and the same thing applies there. Hope that helps or reiterates what others have said. I hope you find your problem. By the way, I have a similar if not the same problem, my 1974 70 hp, will go about 23 mph and stops accelerating at about 3/4 of the throttle/forward shifter, but does not kill the engine, just stops eccelerating. We have had alot of rain also, I'm preparing now to check my pulses per min. also. If I find my problem, I will report back, also if anyone has advice for me, I would also appreciate it, (not to hijack your thread or anything.)
I will also be checking my carbs again since that very well could be my culprit as well. Good luck.

Thank you for that information,i will be looking into it. Hope you figure your out as well..

 

[PuddleFisher]

Re: Please help Figure this one out,your a hero

Hang in there beener. I think these guys are giving you a harder time that you deserve. Now, to test fuel pressure with the gauge, it needs to be between the pump and the carb. Try that and see what you get. Another thought i had, is the new fitting in the tank OMC or aftermarket (atwood, etc). If its not the OMC fitting there it would cause the same leaks as aftermarket fitting on the hose due to loose fitment. Maybe your friends hose worked ok on your tank just because it made a better fitment on your tank fitting. Have you tried opening the tank to relieve pressure instead of bumping the bulb? You could give it a try to make sure the tank vent is working. I just joined the forum today to ask for some insight on a boat I recently aquired. Hopefully I have provided some insight and encouragement as well. Good luck

 

[jonjohnson]

Re: Please help Figure this one out,your a hero

I just had my carbs off checked the float hieght, I don't have a manual yet, but I found someone with a 75 70hp that said it was supposed to be at 3/4 in. from base of bowl (without gasket on) to float hanging down, or 24 on a caliper slide, which is what I have. Well two carbs were real close, one was at about 1 1/2" So fixed them all to read 24. Also the jet with a screw above the bowl (believe it to be high speed jet) I believe was alittle clogged on 2 out of three carbs, maybe all three, but now they are clean. One final thing that I forgot about, and found again tonight, was that my intake manifold, or leaf catcher's bolt holes on the carbs where it fastened to, are stripped on the top carb. So that the manifold is not tight on that carb, you can see light between the leaf catcher/air box (or whatever you call it ) so I'm not sure if that is not the reason the P/O had that one float so low (1&1/2 in. instead of 3/4in. or 24) So I am wondering if I can seal it with some non-gas-permeable sealant? one that will still allow the seal to be broken for next time I take it off?? Again this is just a follow up on my previous post, and I can make a new thread if I need to. any advice will be appreciated. Thanks.

 

[jbeener1]

Re: Please help Figure this one out,your a hero

Hang in there beener. I think these guys are giving you a harder time that you deserve. Now, to test fuel pressure with the gauge, it needs to be between the pump and the carb. Try that and see what you get. Another thought i had, is the new fitting in the tank OMC or aftermarket (atwood, etc). If its not the OMC fitting there it would cause the same leaks as aftermarket fitting on the hose due to loose fitment. Maybe your friends hose worked ok on your tank just because it made a better fitment on your tank fitting. Have you tried opening the tank to relieve pressure instead of bumping the bulb? You could give it a try to make sure the tank vent is working. I just joined the forum today to ask for some insight on a boat I recently aquired. Hopefully I have provided some insight and encouragement as well. Good luck

Thank you for the encouragment,i needed that but i know these guys mean well and are only trying to help. The fitting on the tank is OMC. I have let the tank build pressure and loosened the air vent off and it did work. Thank you.

 

[jbeener1]

Re: Please help Figure this one out,your a hero

Well i was able to take the carb back off,clean it check the float. Took it out yesterday and same thing,as i was running it i watch the fuel pump shooting small bubble about 1/2 inch down into the carb line,as i went ran the motor long the little bubbles would stretch down into the carb line to about 2" and thats when it would start to acting like it running out of fuel.These bubbles are small that shoot out of the fuel pump.. Hoping to try tomorow to by pass fuel pump and run it..

 

[tjhamms]

Re: Please help Figure this one out,your a hero

As I replyed in post # 48. Did you check to make sure the vent is clear in the carb ?

 

[jbeener1]

Re: Please help Figure this one out,your a hero

As I replyed in post # 48. Did you check to make sure the vent is clear in the carb ?

If your talking abut the screen thats in the intake then no i havent check that..

 

[jbeener1]

Re: Please help Figure this one out,your a hero

As I replyed in post # 48. Did you check to make sure the vent is clear in the carb ?

On the carb im able to blow threw at ports of the carb.

 

[tjhamms]

Re: Please help Figure this one out,your a hero

The upper half of the carburetor, above the float chamber. Get a magnifying glass and look real close its a tiny pin hole. It may be partially clogged. Again this is how the air bubbles you see are able to escape. Good luck

 

[Joe Reeves]

Re: Please help Figure this one out,your a hero

There's a very old story about a fellow who owned a car that had a problem he couldn't solve. He had tried everything he could think of and had incorporated ideas from all his friends but still... the problem persisted. One day, a friend of his unscrewed the radiator cap and held it high while another friend moved the car out from under the cap, and as that car moved out, another car was moved in. The friend then lowered the radiator cap onto the replacement car and tightened it... problem solved.

Now, your engine doesn't have a radiator cap but it does have a hood.

 

[nwcove]

Re: Please help Figure this one out,your a hero

lol.....Joe, are you suggesting the op should buy another "car", or that his "car" may have an exhaust leak under the bonnet??

 

[Tim Frank]

Re: Please help Figure this one out,your a hero

Self-Edit:

 

[watchman926]

Re: Please help Figure this one out,your a hero

One of my smaller 5.5 motor has a small plate that the inlet fuel hose goes on. When you take it off there is a valve system that looks like gasket material. It covers the opening from the gas tank and the pathway into the bowl. When the piston pushes compression that seals the opening out to the fuel inlet, which stops air from the engine from going into the fuel line. When it stopped working once, air pressure was forced into the gas tank and out the vent on the lid. Keep in mind that mine has a gas tank on the motor but will also allow for a large tank to be hooked up. Does your engine have the backflow valve?

 

[durban]

Re: Please help Figure this one out,your a hero

mmm... you seem to be getting closer to the problem ? good luck

 

[Fed]

Re: Please help Figure this one out,your a hero

The OP knows what's wrong he just hasn't fixed it yet.

 

[jbeener1]

Re: Please help Figure this one out,your a hero

The OP knows what's wrong he just hasn't fixed it yet.

If i knew what was wrong then i would fix it....:joyous: