omc 3.8 bogging down

[john4040]

This boat is driveing me nuts. I just bought this boat it is a 85 chaperall with a 3.8 chevy and a omc stern drive. The engine will idal smooth as
ice but when i rev it up in gear or in nutral it boggs down and will not rev up not like a misfire just wont rev and backfireing through carb. I have replaced cap rotor wires plugs coil fuel filter and water separator points and condensor. timing is at 8 degres compression is good 155-175 all cyl
Old plugs black and dripping fuel. After replaceing all this it is not popping out the carb anymore but still bogging down. when i replaced water seperator there was water in fuel and fuel smelled old. What i want to know is can water or bad gas do this and still idle so smooth.

 

[Howard Sterndrive]

Re: omc 3.8 bogging down

are you aware of the need to watch which lobe of the distributor cam you are on when choosing #1 on the distributor?
The 3.8 is a semi-even firing motor and therefore a bit tricky to time initially. There is a Mercruiser bulletin on this if you aren't already aware (OMC manuals say nothing about it)

point arm should be on a rounded lobe for #1 as shown or your timing will be all out of whack

 

[john4040]

Re: omc 3.8 bogging down

good to know and it was wrong but still have issue. set dist in set timing and dwell. started to adj carb and when i screw the adj screws in all the way engine still idles and when i open this thing up and it starts bogging i can look into the carb and see that it is dumping fuel thinking i have a carb issue?

 

[Howard Sterndrive]

Re: omc 3.8 bogging down

sounds like a carb rebuild is in order unless there is gas flowing in that yellowy clear hose from the fuel pump to carb- that would indicate a fuel pump failure.

 

[john4040]

Re: omc 3.8 bogging down

Well i got the carb back they rebuilt it flow tested adjusted it. I put it back on and still have the same issue. So I unpluged the esa and still have the same issue. I got a gas can full of new gas same issue. checked fuel pressure (good). THIS THING IS DRIVING ME NUTS. It is not a fuel issue
I will say that the idle is smooth as can be and if i slowley lev it up it will run great till about 1500 than it starts missing a bogging down. Distributer? NEED HELP

 

[Howard Sterndrive]

Re: omc 3.8 bogging down

you could remove the points plate from the distributor and have a look at the advance weights and springs to make sure they aren't all rusted in there.

 

[john4040]

Re: omc 3.8 bogging down

I think i got it I removed the dist took it apart cleaned it greesed it and installed new points. Sounds great revs up smooth to 4500 going to the lake friday

 

[john4040]

Re: omc 3.8 bogging down

Thank you for all the help

 

[john4040]

Re: omc 3.8 bogging down

So here is how it went put the boat in the water and it ran great for 2 hours than it starting acting up. When i give it throttle it would cut out. I was able to go slow on the gas and get it to work sometimes. Then i let it sit and cool off and it would be fine till it got hot. Smothing is getting hot and failing with the ignition. coil?. Will a esa do this? Definately not fuel no sputter just cuts out fast.

 

[Bridar]

Re: omc 3.8 bogging down

Yeah, it could be the coil. I've seen 'em act up when they get hot.

 

[astuckey]

Re: omc 3.8 bogging down

With the boat in the water, attach a wire to the positive side of the coil. Then try to get onto a plane. Then with the throttle down, touch the other end of the wire to the positive side of your battery. I am having pretty much the same problem. Do not use 12 volts all the time or you will burn up points and many the esa too.

 

[john4040]

Re: omc 3.8 bogging down

Well this time I replaced the coil, anti siphon valve, and the esa module and the boat ran great all day. Ran a full tank of fuel through it. Thank u all for all the help