95 Maxum 1800SR 4.3 hesitating bad at half throttle to full throttle after warmed up

[ed & inge]

succes with your problem..

greatz, ed

[ussoldier_1984]

Carb was clean and the metering jets on the primary and secondary were fine no clogs accelerator jets were good too. no dirt or jelled gas in it. So the only 2 things left to do is check to see if the fuel tank has a clogged vent line and replace the distributer module (the chip inside the distributer that senses when to fire the coil) Ill start with the fuel tank first do you think disconnecting the vent line from the tank and blowing compressed air through it will tell me if it is cloged?

[ed & inge]

sure....but clean the vent exit also.....check the line from the tank to the fuel pump also, and from the fuel pump to the carb........check your new fuel filter for water......if thats all oke its got to be a problem at the engine.........but what (i am going to read on the dutch boaters forum if there's said something about this)

greatz, ed

[ussoldier_1984]

Thankyou ohh I cant find gaskit kit for my carb mercruiser stop carying a rebuild kit for it according to my local marina does anyone know of a good website to find the gasket kit or rebuild kit for my carb?
And do you think it could be a problem with the hydrolic lifters? maybe not opening the valves fully after 30 mins? but then again the engine is at full temp within 10 mins and it still runs great up untill about 30 mins. IM thinking it has to be a vent issue on the boat or fuel delivery problem

[ed & inge]

thats why we advise you to check the fuel line from the inlet all the way to your engine...........maybe a slowly growing vacume in the tank........tell us what you found......succes

ed

[ussoldier_1984]

well after alot of research on rebuild kits for the weber 9600s carb they do not make it anymore but edelbrock uses the design on their 1405 carb it is the same as the weber 9600s and thats where you can get the carb rebuild kit for it, (same carb just under new manufacturer) if anyone else needed to know

[ss3964spd]

Definately not the engine's valve lifters.

I think you need to stick with the symptom; runs fine in the 1st 30 minutes, but won't run past part throttle after that. Carb's are not going to be fine for 30 minutes and then crap out.

I firmly believe you have either a fuel flow problem or an ignition problem related to heat.

Another on the water test - if you have the space to perform it. Take the boat and run it for 15 minutes to get it warmed up. Then, before the symptom shows up, run the boat at, say 3500-4000 RPM for 30 minutes without backing out of the throttle if possible. See what it does.

[ussoldier_1984]

Ill have to try that when the carb is back on

[seapuppy]

that's easy to do...run it till it starts slowing down..then open the tank fill cap....if you hear a hiss...you know it's the vent...



SP

[ed & inge]

yeah SP we all think a little bit the same.....so it's got to be that......

greatz, ed

[ussoldier_1984]

I am ordering the carb rebuild kit should have it in a week found a great website with mercruiser parts at really good prices I ordered my transom kit from them for 90 bucks it came with all the gaskets and gimbel bearing the bellows for exhaust drive shaft and shift cable along with a new shift lever inside the outdrive all the hose clamps that you need to install and do a bellows and gimbel bearing, The website is www.amarket.com the carb rebuild kit is 30 dollars from them. Anyway back to the matter on hand after I get my carb back together the first thing im going to do is when the boat starts hesitating I am going to take off the fuel cap and I will let you guys know what happened

[ussoldier_1984]

Might have figured out the problem!!!! Today I disconnected the vent line from the fuel tank and with ease blew and sucked so its not a vacume issue then i took the check valve off the the fuel supply line and went to blow through it it was very difficult to blow through (yes I made sure I was going the right way with the check valve) on a good check valve how hard is it to blow through it?

[seapuppy]

in one direction it should be easy...it the opposite direction you shouldn't be able to blow at all...

might be the antisyphon valve...
SP

[ussoldier_1984]

well im going to replace the check valve is it ok to use a fitting that dosent have a check vavle? what is the point of a check valve?

[ussoldier_1984]

still having the same issue complete new fuel system installed rebuilt the carb new fuel tank fittings. I can not figure this out. fuel tank is good vent on tank is good dont know where else to look for problems any help would be very helpful

[ed & inge]

pppppffffftttt......this is making me sleepless......

do a compression test, change the sparks, is it running on time (ignition) do these tests in the beginning and after it's running bad........

after this i dont know were to look anymore

greatz, ed

[ussoldier_1984]

already checked compression timing is perfect and it has new plugs and wires

[ussoldier_1984]

I might have an answer to the issue. I was told by a merc mechanic that the fuel lines were to close to the engine along the intake and the heat of the engine causes the fuel to vaper lock gonna try to put somthing to insulate to see if thats it

[ss3964spd]

I'd be very surprised.

There is more fuel flowing through the line at higher engine speeds. Since the fuel in the tank is cool, and since it is flowing through the line at a faster rate - effectively cooling the line, then I can't see how it would cause a vapor lock.

Regardless, stranger things have happened. Wrap the line with crumpled tin foil.

Dan

[racer2c]

My sister had a similar problem with her 4.3ltr...turned out to be water in the tank and separator. I knew a guy with a '63 Vette that would stall at stop lights due to vapor lock in the middle of summer but the engine was idling.