Rochester 2bbl bogging under load

[freelunch]

I have a 250 c.i.d. L6 mercruiser with a rochester 2bbl carb.
My question is why does the boat bog down when I lean on the throttle from a stop?
The timing is set at 8 degrees btdc and the dwell is set to .018.
The advance mechanism in the distributor is functioning normally as well.
I also recently rebuilt the carb with a sierra kit. The kit included a new accelerator pump.
When running it on the muffs everything seems to sound great, as it will rev right up, however, when in the water, it bogs down like im trying to tow an iceberg.
Some help would be greatly appreciated

 

[ziggy]

Re: Rochester 2bbl bogging under load

point gap is .016". but it's better to use a dwell meter to set the dwell. dwell is 31-34 degrees. timing is 6 degree BTDC. set dwell 1st, then timeing. adj. when engine is at idle speed. 500-600rpm. i suppose it could still be the carb. but i'd get the ign. set proper first....

 

[freelunch]

Re: Rochester 2bbl bogging under load

Thanks, but I have a question regarding the how i set the dwell degrees? I was told that it wasnt possible because my distributor cap has no window? How do you do it ?
And if that isnt the issue do you have any other ideas about the carb?

 

[Haut Medoc]

Re: Rochester 2bbl bogging under load

You just have ti fiddle with the dwell....
It may require removing the cap a few times to get it right.......
It revs up well on the muffs because it isn't doing any work...
.IE = no load.......​

 

[freelunch]

Re: Rochester 2bbl bogging under load

Thanks for the replies guys, but would either of you or anyone be able to explain how to set the dwell with a dwell meter?
its outlined in my manual but not very clearly and almost left me with more questions than a certain idea on how to do it.

 

[ziggy]

Re: Rochester 2bbl bogging under load

ya can have yer dwell meter hooked up. ground yer coil lead and crank it over with the cap and rotor off. watch the dwell on the meter. while cranking, ya tweek the point with yer flat blade to get the dwell ya want. like haut says ya may need to do it a couple times to get it where ya want it. do check it after ya've got it set to be sure it didn't change. i don't know if it's nesseassy. but i run my hose even while settin dwell. them impellers get eatin up so fast w/o water...

a starting point for settin dwell would be yer .016" point gap.....

 

[freelunch]

Re: Rochester 2bbl bogging under load

ok im confused though. wouldnt i be adjusting the point gap away from .016 when changing it to set for the dwell?

 

[ziggy]

Re: Rochester 2bbl bogging under load

i'd venture to say that .016" is 31-34, probalby 32.5 degrees. set it for dwell and don't bother with the gap. i really think the gap spec. is for an inital set. then dial it in with the dwell meter to anywhere in the spec.....least that's the way i see it.....

 

[freelunch]

Re: Rochester 2bbl bogging under load

Oh ok, gotcha, I wasnt sure if I was tracking there. Well aside from the dwell in that case, what could be causing the boat to bog down like that

 

[Bondo]

Re: Rochester 2bbl bogging under load

If it IS a Fuel Issue,.....
It Could be, the Gas Tank, the Tank Pickup, the A/S Valve at the top of the tank, the Lines, the Fuel Filter, the Fuel Pump, Or the Carb............

Take your Pick.......

 

[Silvertip]

Re: Rochester 2bbl bogging under load

Dwell angle is set using an dwell meter to measure the point gap, hence dwell angle electrically. It is exactly the same as using a feeler gauge to set the point gap only the dwell meter is more accurate and leaves little room for error. Using a feeler gauge you need to find the high spot on the cam lobe. Chances are you will be very close either way. Just so you know, an engine running on half its cylinders will rev quite freely with no load.

 

[freelunch]

Re: Rochester 2bbl bogging under load

Ok, everything, including the tank, lines, pump, and filters have been checked and are all good to go. I really doubt I'm running on half my cylinders as well. Another fact I forgot to mention earlier is that I am getting occasional backfiring through the carb.

 

[John_S]

Re: Rochester 2bbl bogging under load

I don't know specifics about your engine or carb, but the general things:

After re-doing dwell, did you recheck timing?

Did you do the rest of a tune-up?

- new plugs?
- new cap & rotor?
- Adj idle mixture?
- adjust idle speed?

If so, do you have a steady stream of fuel out the nozzles when you depress the accel pump? Do you have an adjustable accel pump arm (multiple hole positions in arm)?

Was the bog there before you rebuilt the carb?

PS: The backfiring might mean that you are running lean.

 

[Bondo]

Re: Rochester 2bbl bogging under load

Ok, everything, including the tank, lines, pump, and filters have been checked and are all good to go.

So What psi. is the Fuelpump delivering to the Carb,..??..??....

This only leaves the Carb..... Probably time for a Rebuild Kit.....

'cause the Symptoms you're describing Still says it's running Lean.......

 

[I/O WALDO]

Re: Rochester 2bbl bogging under load

Sounds like slack acc.pump charge to me.

 

[ziggy]

Re: Rochester 2bbl bogging under load

if the fuel pump pressure test it good. i think i'd recheck my float level.....i've had float level adj. cause me greif before for not gettin it right....

 

[freelunch]

Re: Rochester 2bbl bogging under load

The pump is delivering 5-7 psi of fuel to the carb. I have recently rebuilt the carb which included a new accelerator pump. I will try double checking the float level. Thanks

 

[ziggy]

Re: Rochester 2bbl bogging under load

fuel pump pressure spec. is 3.5- 4.5 psi........

 

[freelunch]

Re: Rochester 2bbl bogging under load

Is there anyway that could cause a problem

 

[FreeBeeTony]

Re: Rochester 2bbl bogging under load

How big is the boat?
Are you under powered?

Is this a new problem?