Flooding/fuel in oil
 

I seem to be burning an excessive amount of fuel and it smells real rich out the exhaust. It also smells gasy just sitting there. I checked the dipstick and it is hard to tell if I have gotten any actual volume of fuel in the oil but definately smells gasy. The boat starts up real good, seems to run well but a little boggy like it is over-fueling in mid range as well as top end. If the boat sits for awhile after running, even just a minute or so, it seems to flood and I have to give it WOT to start again. Any suggestions on where to start in the carb or what to do? Does anyone suggest flushing the crankcase or just put new oil in after the flooding problem is fixed? I have also heard from some people that it is common nature for and I/O to start a bit harder after sitting for a bit because of all the heat that has no where to go in the engine compartment? Was also told to leave the blower on full time?

Would like to go back out again this weekend but need to get it running a bit better. Does anyone have a rough idea of typical fuel cosumption for the 4.3l LX 4 barrel assuming misc cruising, tubing, boarding etc?

thanks

Kurtis, 2 things that come to mind are choke and well plugs in the carb base. Check and see if the choke is open when the engine is warmed up. If it is, it's likely the well plug or plugs. These are holes in the base from the casting of the throttle body. There are soft lead plugs pushed into these holes to block them, one could have developed a leak.

I'd get this fixed as quick as possible, that fuel is at least thinning the oil, or worse, raw gas could be running down the cylinder walls rinsing the oil off!

Probably a carb rebuild would be my guess...

Good luck!
Doug

How do I know if the choke is open? Just by looking at the butterfly? What if it is closed once warm? How do I fix that?

Thanks

Yeah, take off the spark arrestor over the carb and see if the butterfly is open when the engine is warm. As far as how to fix it, if you're not pretty mechanical, they're a tough fix. Carbs are pretty complicated and I'm not sharp enough to diagnose a how to on here. If the choke is stuck, that's not as serious as something inside the carb.

I think I'd take it to a shop to get looked at Kurtis...

Looks like it is a vacuum operated choke? If the choke was stuck on then the boat shouldn't idle smoothly should it? If it is like a car then it should take a couple pumps to get it started then it should want to choke and high idle until either you manually kick it off or the electric or vacuum in my case releases it? does that sound right?

I just sucked all the oil out and volume wise I don't have any gas in the oil. the oil was nice and thick before I warmed it up as well. I did notice that there is a lot of gas just sitting in open cavities inside the carb near the 2 rear barrels?

What is normal fuel consumption for this boat?

Was on the water for the first time this last weekend and still having the same problems. I have been on some other sites and some people say to check the clear tube from the fuel pump? I don't think I have a choke problem as it starts good when cold and runs fine except it seems rich. It starts hard when warm(vapour lock) but I can work with that. I can't be changing oil every weekend and risking damage to bottom end bearing/cylinder?

If the well plugs were leaking how would that cause extra fuel to go through? Where on the base of the carb are these plugs? How do you get them out to replace just encase they are leaking?

What position should the accelerator pump be set at? Mine is set in the middle hole?

Is there no one out there that has any insite on this? I have since checked and I don't have a clear tube from pump to carb like some others are talking about. I have noticed excess fuel pooling in cavities on either side of the butterfly's(4 barrel area-rear of engine??)

Please help.

It could also be a problem with the float. Any way you look at it, unless you are mechanically inclined, you're probably best leaving this to your mechanic. He'll have the tools and the knowledge to repair it correctly and get it adjusted properly.

Thanks for all your feedback. I ended up taking the carb apart last night(nothing to it). There was a fair amount of gummy gas deposits floating around but no jets were plugged and the needle/seat assemblies appeared to be in good shape. I didn't think to try and test the floats but I did make a minor adjustment to one of them that was a little out. I set it to shut fuel off sooner. The floats in this carb are the brass looking metal floats that appear to be braised/welded together. There was nothing evidently inside the float (assuming possible hole or crack). However I did note that there wasn't as much fuel in the bowls as there should have been which means float or needle and seat? I am hoping there was either a minor problem with that one float or possibly some crud getting caught in one of the needle/seat assemblies?

The other interesting note from WetWilly is the choke. When I removed it I made note of the choke position etc and when cold the choke plate is completely closed. But I seem to remember it NOT being completely open once warm. It was open but only a small amount...unless it doesn't actually open to straight up/down. I am on my way out the garage to install the carb back on and check things out with the choke. It appears that it is a combination of vaccuum and manifold heat that opens the choke plate up once warm? Any more insight on the choke would be great.

Thanks

Time for a Reman Carb!!!
 

So much for that plan. Went out for the day and I have gas in the oil again. I think I am going to go with a reman carb. Any suggestions? Some people around here tell me to check into aftermarket carbs such as Edelbrock? I need something in fairly short order so any help or suggestions would be appreciated.

Ordered a reman today from Guaranteed Carburetors. They are very busy right now and have to build a carb for my boat then ship so looks like I'll be down for about a week and a half.

Hope this helps
 

I realize this is an old post; however, it’s my hope this will help others as well. When I purchased my 1995 Mariah Talari, 3.0LX last year, I experienced a similar problem. The person whom I purchased the boat from could not start the engine unless it had not been started in a very long time.

After taking a compression check (excellent results…all 4 cylinders, 160 +/-2 PSI) I purchasing the boat AS IS, I found fuel leaking from the spray bar several minutes after trying to start the engine. Ah! I thought, the problem must be the float setting. The engine ran great after setting the float. I shut the engine down it would not restart…yup, fuel still dripping from the spray bar.

This time I thought: it must be the needle valve and seat. I purchased a carburetor rebuild kit and completed the rebuild taking care to set the float correctly. To my utter surprise, the problem was still there. How can this be?

I connected a pressure gauge to the fuel system and measured between 7-9 PSIG. The manual stated about 6 PSIG maximum (I don’t remember the exact values). This engine had a vacuum type fuel pump; to increase the fuel pressure the internal spring rate had to increase. To this day I don’t know how, but that is what I had. To remedy the problem I installed a Holley fuel regulator and set it to 5-1/4 PSIG. This corrected the issue…running great ever since. I’d love to hear how the vacuum pump can deliver too much pressure. To my knowledge, there is no relief valve in the pump.

Wow. Never thought that could happen. I would have thought some of the techy guys would have chimed in on this post? My fuel pump is electric but I would still like to know what my fuel pressure is suppose to be and if is is possible that is is also my problem? I have ordered a new carb as well but it is not here yet so I still don't know if my problem is in the carb or ??

Hi Boarder1010:

I purchased an after-market manual for my engine and outdrive; unfortunately, the book is at my Florida home and I'm in Connecticut.

I seem to remember, the old flat-head Fords had a similar problem: if the fuel pressure exceeded about 4 PSI the needle valve, seat and float assembly could not shut the fuel off completely. Back then, about 150 yrs ago ;-), in the late fifties to mid sixties we used to disconnect the vacuum pump and replace it with an electric pump and adjust the pressure to prevent flooding.

I'm trying to remember the name of the publisher...I'm told, memory is the second thing to go; I forgot what the first was. ;-) I believe the name is about five letters long and begins with an S. The name is not a common name.

What engine do you have? Is the electric fuel pump original to your boat? I assume you can adjust fuel pressure. A word of caution: Ensure your fuel pressure is high enough; if too low, your engine may run lean. A lean engine will run hot and can cause severe damage to pistons, cylinders, valves and heads. Maybe somebody else can help here: does anybody know what Boarder1010's fuel pressure should be?

Another thought: contact the carburetor manufacturer and ask them what the fuel pressure should be.

Hope this helps!!!

I just went back and reread the posts: Moondance100 and WetWilly had great thoughts. Other than the problem I had with my fuel system, I have NO experience with boats. However, over the years I have had a fair amount of experience with carburetors used in autos and aircraft.

The choke must be wide open when the engine is at operating temperature.

Moondance100 had another excellent thought: the plugs used in the carburetor during the manufacturing process to seal the drilled passages could be leaking.

Since you do not have a vacuum pump the only way I see for fuel to enter the crankcase is though the carburetor. In any case, when you replace the carburetor with the corrcect one and verify your fuel pressure, your problem should be solved.

P&W what is the part # for the fuel pressure regulator you used? I am assuming you just tee'd into your line somewhere? My fuel line is steel so I am planning on using a rubber hose in order to tee in to check my pressure this weekend. I am not sure if it is the original pump or not....could have been replaced with the wrong one? I only bought the boat last fall and it has always flooded. I was hoping to check the pressure and if high, get it set and try to get away without replacing the carb? My experience with electric fuel pumps on cars and sleds that have EFI, tells me that there is usually a return line going back to the tank so that the pump can dump fuel back when idling etc so as to not overheat the pump. What will happen if I regulate the pressure back without a return? Is there a chance of overheating the pump? Is there a part # somewhere on the pump? I can't see it from the top. Perhaps if I remove the pump and locate the part #, I could verify it is the correct pump.

I did get ahold of the carb reman shop and they suggested a max of 5 psi. Not sure but I am assuming that is at idle? With an electric pump it should be the same all the time anyways?

Hi Kurtis, unfortunately, the boat is in FL; I'm in CT. However, I purchased the Holley regulator at NAPA. The item I purchased does not have a return line...which I thought was very unusual. I did not know if it was going to work, but I tried it and it worked very well.

The unit I have has NPT connections. I would recommend not using teflon tape; use a thread compound suitable for fuel. I did not use hose; I used a double flare on the 3/8" metal tubing with brass fittings (3/8" flare to NPT). Also, I would not use copper tubing because copper tends to work-harden under vibration.

I certainly do not want to give you bad information. If anybody out there has any comments, most importantly, if they do not agree with what I'm stating, PLEASE COMMENT!

Thanks,
Bob

Kurtis, if your pump is adjustable you probably will not need the regulator. Just adjust the pump's internal pressure relief valve to provide the proper pressure.

Hope this helps,
Bob

Bob,
How can I tell if I have an adjustable pump. It does not look adjustable? No screws I can see from the top. I may have to pull it off to see? It looks factory or perhaps replaced at some point in its life but painted black to match exactly as everything else?

Still not running?
 

Ok. So I finally received the reman carb, found a fuel pressure regulator and dialed my pressure down from 6.5 to 5.0 and hit the water. What do you know...runs worse than it ever has! So I called the carb place and they now think I may be starving the carb for fuel. Perhaps the fuel pressure regulator has reduced my fuel volume to the carb? I am going to do a volume test on the carb tomorrow to see what I have for volume before the regulator and after the regulator. So far in the little driving I did with it on the weekend I don't think I have any gas-in-oil problem anymore which could be a function of the new carb, the lower pressure or the lack of fuel volume? Basically I only had the primary circuit working and if I tried to open it up it was a solid bog(possibly lean?) Yet a couple times it was hard starting after sitting for awhile much like before with it over fueling.

What are the thought's out there on this situation now? Any idea on the volume I should be looking for. The Carb place told me 1 pint in 15 seconds as a minimum?

We have the four barrel 4.3 and I'll have to admit I have been surprised how little gas we have used compared to what I thought. We did two heavy days of slalom and regular skiing and also plenty of single tubing besides just seeing how fast it would go(52 mph)and still only used about 15-20 gallons.

Just encase anyone is still actually reading this post I thought I would put in a final blurp. I checked my fuel volume and I was getting just over a pint of fuel in 15 seconds after the regulator and about 20% more than that before the regulator. So in theory I should have enough volume after I regulate the pressure, even though it did reduce the volume while reducing the pressure. So I put the old carb on and removed the regulator to try to get things back to the way they were before I started this project. But it still wouldn't work. Then I remembered I had made another change while waiting for the carb to ship to me. I had changed the plugs, cap and rotor. With everything else being constant I thought I would try and switch it back. I put the old cap and rotor on and a-way she went. This was my problem.

How can it be that it started perfect, idled perfect and ran really good up to about 1/2 throttle with the new cap and rotor but when I opened it up it fell on its face? I don't understand how this ignition system works? At any rate, I currently have a rebuilt carb, fuel pressure adjusted to 5 psi, new plugs and old/corroded cap and rotor. I still have slight bog under full acceleration and since the other bogging problem ended up being electrical, my question is could I still have a minor electrical problem causing the bog? I used NGK plugs and gapped them according to the spark arrestor cover(.035 I think), and the cap and rotor came from Napa but were definately Marine parts and everything was identical? Should I consider getting genuine Mercruiser parts? What else could cause the slight hesitation/bog?

i have had this problem a couple of times. i live in Louisiana and it is very hot. your problem is vapor locking. after it has been run, let idle for a minute or two to cool down and have your blower on then shut off or shut off and raise the hatch. it doesn't have too many vents to breathe. there is no need to leave the blower on but it wont hurt.

Long distance diagnostics
 

Hi Kurtis:

As I read the thread now it appears your intial flooding problem has been corrected; now the problem is related to loss of power while approaching WOT. Is this correct?

Typically, the inability to produce power under load is caused by ignition problems. However, I believe you have a 4.3 L engine. I am NOT familiar with that engine. Having stated that: if that engine has a 4 BBL carb with a vacuum operated secondary, it is possible when manifold pressure drops causing the secondary to open, if no (or not enough) fuel is delivered, the engine's power will drop significantly...basically, the engine is "flogged" due to leaning out.

If vacuum operated, try to lock the secondary in the closed position. If the engine still bogs down, I'd look at ignition. If not, ensure you have enough fuel to the secondary.

When I had the fuel problem, I attached a "temporary" pressure gauge to the regulator 's output port...I left the gauge in place just in case the problem reoccured...that was over a year ago.

Is it possible under WOT your fuel system is not delivering enough fuel? A pressure gauge will let you know. Though it may not let you know if the secondary has enough fuel. Is it possible, without taking the carburetor apart, to verify the secondary's bowl has enough fuel? Years ago, some Holley 4 BBL carbs had screws to be removed when adjusting the float while the engine ran. The float was adjusted until fuel just began to leak from the screw hole. I'm not suggesting you adjust the float or anything else; only a possible means of checking the fuel level in the bowl.

I don't know if it would help, but I have a picture on my laptop of the installed regulator and "temporary" fuel gauge setup. I would include it but I do not know how to upload the file.

Bob

Thanks again for your insite Bob. I guess at this point I am quite confident that I have enough fuel and the proper pressure to prevent flooding. I still have not purchased a new Mercruiser cap and rotor as I am still wondering how this ignition works? Shouldn't the distributor have a vacuum advance? There is a small port coming out of the distributor cap that goes nowhere inside and also there is no vacuum hose to attach to it? How does this system get its spark advance?

If it's a Thunderbolt igniton system, the module on the distributor electronically advances and retards the timing.

Flooding/fuel in oil
 

it sound as if your Choke could be stuck closed or partially close. Check by removing Flame arrest-er and visually looking at the Choke butterfly. It should be wide open and free to move very shortly after starting as it is electrically deactivated and mechanically activated. If the Choke is good it could be that your float has dropped and this will cause flooding. also a bad needle and seat valve will cause the same symptoms. If you suspect that it's flooding and the choke is OK have an experienced mechanic fix the other issues. It might cost you a little to have it fixed properly but it is much cheaper than have a mishap on the water. gasoline fumes in the bilge is a very serious condition. I had a similar problem with a Celebrity I had last summer and overhauling the Carburetor fix the problem.
Good Luck.

Re: Flooding/fuel in oil
 

Hello All. Sorry but I am going to reactivate this post once again as I am still not 100% satisfied with my boat. To recap - I am installed a new carb from Guaranteed Carburetors, new cap and rotor this year (original OEM Merc), spark plugs last year (NGK), did not change wires or check timing, installed the fuel pressure regulator and have the flooding problem under control. The boat starts perfect every time and runs great on the mains but when I need secondary (4bbl) it still bogs like perhaps it is lacking fuel or timing. I am sure it is not short on fuel as I have installed and tested the regulator and it is within spec for my carb according to Guaranteed Carbs. Also I still have the hard starting problem after shutting down and letting it sit for more than a couple minutes. It does not start any better or worse if I open the deck when I stop. It is definately partially flooded when I go to start it because if I go to full throttle when it won't start it fires almost immediately. If I don't do anything and just turn it over it will probably take 10-15 revolutions to fire up. I did not check to make sure I have the Thunderbolt ignition but it is a 95 barchetta with 4.3LX so perhaps someone will know what I have and confirm that I have electronic spark advance? If so why do I have a port on the distributor cap? What should I try next?

Re: Flooding/fuel in oil
 

Hi
A couple of thoughts on your problem first it sounds as though your carb is still flooding a little, have your float level checked if it is just a touch high it will run OK under way but will allow excess fuel to over flow into the manifold when shut down not much will cause the restart problem you explained. The second problem of bogs when secondaries open was very common in the early spread bore carbs. the float chamber is a touch to small for the large amounts of fuel required at WOT re jetting may help there I would try a size or two larger and see what that does, timing may also help, make sure the accelerator pump is in good shape. I have had a couple of Mercarbs that were jetted to lean from the factory (poor throttle response, Ski Boats) Your plugs will tell you a lot if you read them, the color of the porcelain tells wonders.
Good luck
Wonsnam
Talai Z201

Re: Flooding/fuel in oil