[boarder1010]

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?

[WetWilly]

Hi boarder1010,

According to the 4.3L service manual, your pump is not adjustable. As a matter of fact, they say it is not repairable either and must be replaced it if has any problems.

WetWilly

[boarder1010]

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?

[Tom]

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.

[boarder1010]

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?

[cole]

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.

[P&W_43yrs]

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

[boarder1010]

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?

[Z 202]

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

[wonsnam]

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.