1989 Bogs and shuts off after WOT

[vince champion]

Re: 1989 Bogs and shuts off after WOT

Thanks alot DON S and J martin for your help. Today i repair/installed my fuel pump also i changed my primer fuel hose and bulb to a OEM mercury one. I also installed a Fuel Water seperater made by mercury too. So wish me luck as i will test this bad boy out today! Hope i can feel the power of WOT! haha thanks again.

 

[vince champion]

Re: 1989 Bogs and shuts off after WOT

What a beautiful day at the lake today. even tho i got skunked its ok at least i was out there in the water. So i tested the boat today and she runs alot better. but once i go WOT she will slowly bog out unless i keep pumping gas into her. and if im going around 10 mph she will go smooth for like 5 mins and i can hear the engine starving for gas so ill give the bulb a pump or two and shes fine again for another 5 10 mins. What problem can this be? I recently changed
1) rebuild the fuel pump
2) add a water/fuel seperater kit
3) change hte fuel filter
4) changed the Primer bulb and hose to OEM mercury.

Also this motor has been service just 7 months ago, Did the carbs and fuel pump. Can this be spark plug problem? Carb problem? Needle and seats? Please help me out. What should my next test be? What should i change out?

thx alot guys!

 

[vince champion]

Re: 1989 Bogs and shuts off after WOT

BTW i forgot to mention, My old fuel pump was dmg. It had a rip on the plastic peice in the middle after i changed that, the primer bulb actually stays hard now when connected to motor. Just when the motor is running for 5 mins or so it will get soft again and another 3 squeeze will get the bulb hard again. So what can this be?

 

[gss036]

Re: 1989 Bogs and shuts off after WOT

I take it that you are running on a built in fuel tank. Is there way you can run on a portable tank? This might help eliminate the pick up line inside the main tank. Or, you may be sucking a little air at one of the connections or around the fuel filter.
I hate to even ask, but, are you sure you got the fuel pump back together right.

 

[vince champion]

Re: 1989 Bogs and shuts off after WOT

Yes i am running on a built in fuel tank. I Can try running on a external fuel tank this weekend. Hopefully that will fix the problem. Its ok gss i think i did the fuel pump correct. My cousin was there with me we were both working on it and hes rather good with motors. Should i take it apart again and put it together once more? Does this problem sound like the fuelpump? if thats the case i will take it apart again. Thx for your help. Greatly appreciate it.

 

[gss036]

Re: 1989 Bogs and shuts off after WOT

Yes it does sound like a fuel pump, but since you feel comfortable with the rebuild, look for other issues. Try using the choke(fuel enrichner) when it starts dying out, if that helps, then that is a little more evidence that you are not getting good fuel flow. How did you install the new fuel line, primer bulb? Is close to the engine and at least horizional, peferable pointed a little upward, almost vertical if possible, so the ceck valve works properly. Recheck the filter/lines to make sure they are tight. If you can see the clear plastic fuel line going up toward the carbs, see if it has any air bubbles, that will tell you that you are sucking air somewhere.
These little things can drive you nuts if you let it.

 

[vince champion]

Re: 1989 Bogs and shuts off after WOT

I will take apart my fuel pump and rebuild it again. I will also try using the choke when it starts dying out. What did you mean about the primer hose/bulb? Are you saying i should cut off any left over hose off? and keep it short as possible? I just recently installed a water/fuel seperater which requires a little more fuel hose and the filter is mounted in the back of the boat which the fuel hose isnt really pointed up. It is more of the same level as the gas tank. The clear plastic line isnt the fuel line is it? on my motor it is the motor oil line. The fuel line is in a blk hose. should i change all my line and hose? thx again gss

 

[j_martin]

Re: 1989 Bogs and shuts off after WOT

The bit about slowly starving at any speed indicates problem getting fuel. You just changed the tank line/primer bulb, so that should be good. Any small air leak in that line will cause this sort of trouble. It could also be a small air leak in pickup tube in the fuel tank.

It could also be caused by an old softened pulse line. Normally that don't happen, but it sounds like you had a lot of fuel going through that line. It might be softening up when it's warming up, and the vacuum pulse that runs the fuel pump is being absorbed by the soft rubber line. It's worth checking.

Restriction, such as a bad bayonet connector, or a plugged filter, would likely cause the most trouble at WOT.

If there is a check valve on the tank, remove it.

hope it helps
John

 

[gss036]

Re: 1989 Bogs and shuts off after WOT

I agree w/JMARTIN's post. The primer bulb is what I am referring to on previous post as it needs to as vertical as possible. There is an excellent article over on the Whaler board about the primer bulb, you would need to do a search to find it.
Usually length of hose is not a problem. Again check all your fitting on the new hose and filter assy. There was post the other day I read about the Racor filter not being on tight enough and was allowing a small air leak. I think it was on this board.
(from j-martin's previous post) A piece of clear vinyl tubing (from the hardware store) temporarily installed in the fuel line just before the engine will show any leaks as air bubbles in the fuel. If normal, it should be clear with no bubbles

 

[hkeiner]

Re: 1989 Bogs and shuts off after WOT

Previous posters provided an excellent suggestion that you test the VACUUM in the fuel line when the motor is bogging. Mercury published a Service Advisory describing how to do this (see link below). I think that without doing this test, you could be spending your time and money working on the wrong components. If you did do this vacuum test, what were your test results?

Another good test is to check the PRESSURE in the fuel line between the fuel pump and the carbs. Your shop manual should contain the specs.

Another forum member had symptoms similar to yours, where squeezing the fuel bulb helped the motor run better, and he spent a lot of unnecessary effort working on the fuel lines, the fuel pump, squeeze bulb, fuel line connections, etc. without any success. Very frustrating. After doing the Mercury fuel starvation test, he found that there was no fuel starvation situation (i.e., no increase in vacuum during the bog) and so directed his attention next towards components downstream from the fuel pump. He cleaned his carbs carefully and all was well. (see below link)

Your results may vary, but my point is that using a vacuum and pressure gauge could be the quickest and most effective way to narrow down and/or elimate possible culprits. Sometimes making a diagnosis (educated guess) based upon symptoms works very well, other times it does not. When it does not, I depend on using test equipment, such as a vacuum and pressure gauge in this case, to diagnose.

Good luck

http://forums.iboats.com/showthread.php?t=215710&highlight=starvation


http://www.marinepartsman.com/Mercury-Marine-service-bulletins/Mercury-Mariner/2001/EN_17.PDF

 

[j_martin]

Re: 1989 Bogs and shuts off after WOT

Amen

 

[vince champion]

Re: 1989 Bogs and shuts off after WOT

Thx for all your replies. This weekend i shall take the boat out to test it on a external tank again. This time imma also have a clear tubing on my fuel line in between the fuel pump and carb and on the motor. Hopefully this will solve the problem. If not i will purchase a pressure gauge and i will also clean my carbs. So wish me luck. Thanks again!

 

[hkeiner]

Re: 1989 Bogs and shuts off after WOT

If not i will purchase a pressure gauge and i will also clean my carbs.

The Mercury Service Advisory for fuel starvation testing requires the use of a VACUUM gauge. The PRESSURE gauge test can be done in addition to the VACUUM gauge tests as an additional test, not in lieu of the VACUUM gauge tests. I just thought I would point this out before you go shopping for gauges.

 

[Silvertip]

Re: 1989 Bogs and shuts off after WOT

Think about it! The primer bulb cannot stay firm when the engine is running because fuel is being sucked through it -- that line is not pressurized. It has pressure between the bulb and the engine only during initial start because you "forced" fuel to the engine. You have either a plugged or partially plugged anti-siphon valve, a plugged or partially plugged fuel tank vent, a fuel pump that cannot meet the fuel delivery demands of the engine at wide open throttle, a restriction in the fuel line or primer bulb, or a bad carb rebuild job. If squeezing the bulb causes the engine to pick up again then its a fuel delivery problem. Try running the fuel tank cap open. If it runs ok you have a clogged tank vent. The anti-siphon valve is the metal fitting where the fuel line hooks to the tank. They do stick. Remove it, clean it, and reinstall it. Or simply replace that fitting with a standard barb fitting and try it. The fuel pickup in the tank may also be gummed up or clogged with debris so remove that and check it. As for checking fuel pressure with a vacuum gauge, that's a contradiction of terms. Vacuum sucks == pressure blows. The gauges are different although there are some vacuum/pressure gauges that work both ways.

 

[j_martin]

Re: 1989 Bogs and shuts off after WOT

The Mercury Service Advisory for fuel starvation testing requires the use of a VACUUM gauge. The PRESSURE gauge test can be done in addition to the VACUUM gauge tests as an additional test, not in lieu of the VACUUM gauge tests. I just thought I would point this out before you go shopping for gauges.

If the fuel line or fuel pickup tube is plugged, the primer bulb will be sucked flat by the engine. If there's an air leak, it won't go flat, but bubble will be visible in a clear line. What else would you find with a vacuum gauge?

On the other hand, if the fuel pump if failing, or the filter is plugged, or the pulse line is soft or plugged, the vacuum will be good.

I had multiple faults in mine. I found the bad primer bulb with the clear line. I found the bad pump with the pressure gauge. When I rebuilt the pump, I replaced the fuel filter. The gauge soon showed a drop, and replacing the fuel filter yet again repaired it. That led to finding contamination in the tank and installing a real fuel filter (RACOR water seperating) and chit canning the Mercury junk. Again, the fuel pressure was marginal at WOT and I bypassed the bayonet, completely solving the problem. I rebuilt the carbs, and they needed it because they also were the victim of half *****ed maintenance, but they were not the cause of the flame out at WOT. Carbs seldom are.

hope it helps.
John

 

[hkeiner]

Re: 1989 Bogs and shuts off after WOT

As for checking fuel pressure with a vacuum gauge, that's a contradiction of terms. Vacuum sucks == pressure blows. The gauges are different although there are some vacuum/pressure gauges that work both ways.

Perhaps my earlier comments were not as clear as could be. The Mercury Service Advisory explains this much better, but in short, a VACUUM gauge is used to monitor VACUUM in the fuel line between the tank and the fuel pump. If the VACUUM increases beyond spec during engine bog, then there is a RESTRICTION somewhere upstream of the fuel pump. If there is no change in VACUUM during engine bog, there is NO RESTRICTION and you have eliminated all of the possible culprits upstream of the fuel pump that could cause a RESTRICTION. This can save a lot of wasted effort checking, cleaning, or replacing items that don't need attention. And there are a lot of possbile culprits that can cause a RESTRICTION upsteam of the fuel pump, as pointed out in the various previous posts.

On the other hand, the PRESSURE gauge is used on the fuel line between the fuel pump and the carbs. There is a separate spec as to the normal range of PRESSURE in the fuel line between the fuel pump and the carbs. If the PRESSURE drops below spec during engine bog, you could have a fuel restriction OR a bad fuel pump, but you can't tell which it is using this test method.

Eliminating possible culprits using a gauge can be easier and less frustrating than checking, cleaning, or replacing the many possible culprits only to find that they are not the problem. I got this good advice from someone when I was troubleshooting my own engine bog situation and I wanted to pass on this wisdom.

 

[vince champion]

Re: 1989 Bogs and shuts off after WOT

I appreciate everytime taking their time to explain this to me, as you already see i aint no pro at this im still in a learning process. So i took my boat out 12/21 on my lunch break and ran it with an external fuel tank. The boat still dies out if i dont squeeze the primer bulb. Even at low speed and not wot. So it isnt the fuel tank so i must move on to the next test which is with the clear tubing on my fuel line and also with the vacuum gauge. I will test that out today. Thanks alot again

 

[jimg984]

Re: 1989 Bogs and shuts off after WOT

wonder why nobody uses an electric pump and elemitade the squeeze bulb and engine fuel pump? would have to one with low psi

 

[Silvertip]

Re: 1989 Bogs and shuts off after WOT

There is nothing wrong with the fuel pump designed for the engine. It's simple and reliable. Besides, electic fuel pumps have no way of being de-engerized on a carbed two-stroke. If the engine stalls or there is a fire the pump will continue to pour fuel on the flames. Modern EFI/DFI and 4-strokes have the ability to turn off an electric pump. The ECM knows when the engine stopped and will therefore drop the pump relay. Four strokes and I/Os can use an oil pressure sender to kill the pump. Fix what you have.

 

[j_martin]

Re: 1989 Bogs and shuts off after WOT

Perhaps my earlier comments were not as clear as could be. The Mercury Service Advisory explains this much better, but in short, a VACUUM gauge is used to monitor VACUUM in the fuel line between the tank and the fuel pump. If the VACUUM increases beyond spec during engine bog, then there is a RESTRICTION somewhere upstream of the fuel pump. If there is no change in VACUUM during engine bog, there is NO RESTRICTION and you have eliminated all of the possible culprits upstream of the fuel pump that could cause a RESTRICTION. This can save a lot of wasted effort checking, cleaning, or replacing items that don't need attention. And there are a lot of possbile culprits that can cause a RESTRICTION upsteam of the fuel pump, as pointed out in the various previous posts.

On the other hand, the PRESSURE gauge is used on the fuel line between the fuel pump and the carbs. There is a separate spec as to the normal range of PRESSURE in the fuel line between the fuel pump and the carbs. If the PRESSURE drops below spec during engine bog, you could have a fuel restriction OR a bad fuel pump, but you can't tell which it is using this test method.

Eliminating possible culprits using a gauge can be easier and less frustrating than checking, cleaning, or replacing the many possible culprits only to find that they are not the problem. I got this good advice from someone when I was troubleshooting my own engine bog situation and I wanted to pass on this wisdom.

If there's a small air leak in the suction line, a vacuum gauge won't go out of spec, but the engine won't get fuel. Bubbles will show, and pressure after the fuel pump will drop.

Enough vacuum to go "out of spec" will flatten the primer bulb. Consider it a poor man's vacuum gauge.

'nuff
John