Carburetor Problems, I think?

[JCH55]

1994 Mariner 40 HP, 4 cylinder, Serial number OD295837, Dual Carb.

Removed and cleaned (did not replace any parts) carb parts in gunk this spring because of starting problems. Had to set the idle/mixture screw all the way in to keep motor idling. And also have set screws to a richer setting to make outboard run.

Recently have rough starts and cannot put into gear without stalling, have a lot of gas/oil coming out exhaust.

Can run at high idle, so I dont think it is a fuel pump problem ?

I recently puchased 2 carburetor kits and plan to breakdown and install with new parts.

The primer bulb is hard when squeezed. When I lift the primer bulb above the height of the gas tank, air flows back into the gas tank and the bulb is soft. Is this normal?

I have a fair amount of Oil/Gas dripping from carbs. Is this normal?

Am I pointed in the right direction with the symptoms that I have described? any suggestions?

The kits include most everything, with the exception of the floats, they looked to be in good condition. Why should the floats have to be replaced?

Thanks for your help.
Jim

 

[Barnacle_Bill]

Re: Carburetor Problems, I think?

Your carbs need a thorough cleaning and out back together with new gaskets, needle and seat. Floats normally don't get replaced unless they are leaking or saturated with fuel. You could also have pinholes in the fuel pump diaphram or defective check valves. Also sounds like the check valves in the primer bulb are bad too.

 

[JCH55]

Re: Carburetor Problems, I think?

Thank for your reply.

I forgot to mention that the fuel filter has air in the top half inch of the filter when the primer bulb is squeezed and firm. Is this normal ? or, should the filter be completely full?

Thanks,
Jim

 

[borderboat]

Re: Carburetor Problems, I think?

Me x2 on the fuel leaking out (only when the motor is tilted up for trailering) and the fuel filter thing...

 

[milehighboater]

Re: Carburetor Problems, I think?

The air in the fuel filter is normal, I have seen a bubble in mine plenty of times. About the fuel comming from the carbs, is it pouring out or can you just see some seepage? Also do you tilt the motor up enough for fuel to pour from the mouth of the carb?

 

[borderboat]

Re: Carburetor Problems, I think?

I tip mine all the way up, and the use the factory stop mechinism for trailering. I suppose I should invest in a transom saver and only tip it up enough to keep the skeg from hitting the ground. Would that solve my leaking fuel problem?

 

[Wingedwheel]

Re: Carburetor Problems, I think?

If you want to solve the leaking problem, when you get to the ramp disconnect the fuel line and run the carbs dry before putting it on the trailer.

 

[fiftiesoutboards]

Re: Carburetor Problems, I think?

I just posted the following on another Mariner carb question, and yours sounds exactly like my issue, right down to the inch of air at the top of the fuel filter when priming with the bulb. My check valve in my bulb had come apart, and was pumping gas and air and wouldn't firm up. Sometimes the motor was fine, and other times the pieces would block the fuel flow to the motor. A new bulb or new line w/bulb is the answer. You can confirm by emptying the fuel line and shaking the bulb a bit. If you hear things rattling in there, you've found your problem. Good boating!

 

[JCH55]

Re: Carburetor Problems, I think?

Thanks,
I have completely rebuilt the carbs and replaced fuel pump and filter. Still having same problem. Will try your suggestion of replacing bulb and fuel line the next time I am at the lake. Will let you know how it goes.

 

[trihull59]

Re: Carburetor Problems, I think?

Go to a parts store and rent or buy a compression tester and test each cyl. Take all plug wires off take on spark plug out at a time and replace it with the compression tester. Then crank it over untill the psi won't go higher on the gauge and if it is anything below like 85 your motor is shot 85 is even low a good engine should be right around 120-130

I would do this before you spend any more money on the engine

ps. if the gauge says 0 it likely is 0 and the gauge is not broke

 

[JCH55]

Re: Carburetor Problems, I think?

The compression has been tested and is good at 120 psi on all cylinders.

I have been reading other posts about the enrichment valve possibly being stuck open.

I plan on testing that.

Question, on this 2 carb, 4 cylinder model, when at idle or high idle in neutral, should both carbs be functioning or just the top carb on cylinders 1 and 2 ? In other words, if it it just the top carb, the plugs in 3 and 4 should be dry? Y or N?

I plan on running the boat at high idle (which I can do, just not at low idle, engine kills) and then pulling plugs 3 and 4 to see if they are dry.

Question, if they are wet, what does this mean? What next?

Thanks, JCH55

 

[Wingedwheel]

Re: Carburetor Problems, I think?

Have you tried changing the plugs, or checking the timing? If your getting alot of fuel out the exhaust it might not be firing properly.

 

[JCH55]

Re: Carburetor Problems, I think?

I put in new NGK plugs this spring and tried a new set of plugs about a month ago when these problems started occurring.

I do agree that it does not seem to be firing properly.

Come to think of it, these problems started in the spring before I put the pontoon on the water. I started the motor with ear muffs off the water with last years plugs, it started fine and idled well. I had been blowing a fuse at WOT the past few years. I found a short in the commander and repaired and then ran motor at WOT and the fuse did not blow, problem fixed.

I then changed out the plugs and greased the motor, as I do each spring. The idle problems started occurring before I put it on the water. I had to set the idle RPM screw stop all the way in to its hilt and set idle/mixture screws to a very rich condition to keep the motor running at low idle. Now that I think about it, these issues started after I changed the plugs.

Could I have gotten faulty plugs, twice??

I bought them each time at Fleet Farm. NGK BUHW2's

Sometimes I keep an old set of plugs around, if I find them, I will give them a try. The screws have been set back to their old settings.

Has anyone heard of getting a bad batch of plugs? Maybe Fleet Farm does not go through alot of BUHW2's and both my sets came from the same batch!!

 

[Wingedwheel]

Re: Carburetor Problems, I think?

I've never heard of a bad batch of plugs, but have seen some that were mis-marked. Just a silly question, but did you double-check the gap? How do your wires look, and finally, did you put fresh gas in your tank or just top it off? HeHe I guess thats three silly questions.

 

[JCH55]

Re: Carburetor Problems, I think?

Thanks, Wingedwheel!

Yes, I have checked all your suggestions. It is not the plugs, I cleaned up an old set with the same results, runs at high idle, but not at low.

However, when changing the plugs, I noticed a white milky substance on plug #4.

What are the causes of water in cylinder?

I can run boat with #3 and #4 plugs disconnected. I have arc on #3 and # 4 wires but it appears they are not firing because the wires are not warm like on #1 and #2. This would make sense if there is water getting into the lower cylinders.

Could this be a reed problem?

Thanks, JCH55

 

[Dave1027]

Re: Carburetor Problems, I think?

Could this be a reed problem?

Nope

 

[JCH55]

Re: Carburetor Problems, I think?

If not the reeds, what are the causes of water in lower cylinder?