Merc 140, Bog over 2000K RPM

[Chef Shawn]

Hello All,
1989 Mercruiser 140 (3.0) rebuild...Never idled right or ran great, so this year...

-Rebuilt carb (two barrel)
-New Coil
-New Points, dwell set
-Timing at 6 degrees BTC
-Replaced both fuel filters
-Ran on tank gas and from fresh gas, same result

It fired up fine, idled pretty crappy. I noticed while rebuilding the carb ( I have two) that the springs on the electric choke were in two completely different positions. So I put the choke from the spare carb on, presto, idles better than it ever has, so set it down to 850rpm and got the timing spot on...(this is all on muffs)

Put it in the water yesterday, start/idles great, hit the throttle and nothing over 1800 or so, feels like a bog almost, engine wants to cut out.
Should I set timing while in the water?

Any help appreciated.
Shawn

 

[Bondo]

Ayuh,... Sounds like the Hi-speed circuit of the carb is still plugged up,.... Did ya change the fuel Filters,..??

 

[crewscontrol]

Did you buy this boat used and with this particular problem? If so and if you do not know the boat's history, there are many problems that can cause the bogging problem.

It definitely sounds like a fuel problem to me and I would start there. I know you rebuilt the carb, but did you rebuild it correctly? Did you set the float correctly? Is the accelerator pump in the carb working properly? Are the two brass jets the right size? Did you remove and clean the metering section of the carb? This contraption is located between the two "barrells" and is held in place by 3 screws and contains 4 precision brass tubes with numerous very small holes and passages. These brass tubes must be perfectly clean and all the holes in them must be open. Did you make sure all of the very small drilled passages in the carb base are open?

I just rebuilt the Rochester 2 bbl carb on an old 1965 110HP Mercruiser. This Mercrusier is so old it is painted white and no trim and tilt. There are LOTS of small passages in this carb that can clog and are easily over looked by someone (like me) who does not rebuild carbs very often. I used carb cleaner, compressed air, and finally an oxygen acetlyene tip cleaner to make sure ALL the very small passages in the carb were open. Now my 49 year old 110 Mercruiser runs like a sewing machine.

 

[Chef Shawn]

Yes, Bondo, replaced both filters.

Yes, used boat, but this is the third season I've had it. It was OK the first season and slowly but surely got worse. This year I totally redid interior, so figured if it looked nice, it should run nice. I didn't used to bog, but then again it never idled worth a hoot. I took my time and rebuilt the carb correctly with a kit, every little nook and cranny was soaked, used pipe cleaners, blown out, soaked again blown out with carb cleaner through the baby passages (even took out all the check balls and replaced). Jets matched the old ones, all passages are clear.

Suspecting something with the choke, attached picture shows two chokes, one on the right is from the other carb (which is on the boat now and it starts/idles better than it EVER has since I owned it, but no rpms) one on the left is original (hard start, rough idle, but rpms). See how the coils are nowhere near the same? One is way to the side and the other almost at the top.

Also, I have 12V to choke. And in the water, no load (throttle only) I get rpms.

Sorry, won't let me upload picture....

 

[Chef Shawn]

FIXED*** Human error of course, mine....accelerator pump shaft was one millimeter too far left in the carb, holding screw was hitting, allowing the pump to move 45 degrees instead of the full 90 degrees. Runs like a dream now. If I had a dummy flag, I'd be waving it now....