82 Mercruiser 140 Hesitates and Bogs

[apoc330]

I have a 82 mercruiser 140 in a wellcraft bowrider 180 and I am having problems when accelerating with the engine bogging down.

I recently had the carb rebuilt and it ran great for about 15-20 minutes and then without touching the throttle she just started bogging down and the RPM's fell and now will not climb above 2000 or so while under load.

If I rev the engine up throttle only (while still in the lake) the RPM's climb fine to 3500 and would probably go higher if I tried, but as soon as I engage the prob the engine starts to hesitate and ping.

I was thinking bad gas except it revs fine when not under load, but i am going to put some enzyme in to be safe because the boat sat for 5 yrs before I got a hold of it and started restoring.

Any suggestions would be greatly appreciated.

 

[apoc330]

Re: 82 Mercruiser 140 Hesitates and Bogs

Oh yeah, it has a Rochester 2 barrel carb and I am running on 87 octane unleaded fuel.

The boat never stalls and always starts without much effort.

 

[fat fanny]

Re: 82 Mercruiser 140 Hesitates and Bogs

If it sat for that long I would go through all the electrical connections clean coat and tighten. full tune up plugs wires points condensor and or module and cap/rotor then go for a compression check clean all fuel lines and change filters check anti siphon valve and fuel tank pick up tube screen then check timming and advance.

 

[Bondo]

Re: 82 Mercruiser 140 Hesitates and Bogs

I was thinking bad gas except it revs fine when not under load, but i am going to put some enzyme in to be safe because the boat sat for 5 yrs before I got a hold of it

Ayuh,.. drain the tank,+ add fresh gas,...
Also inspect,+ clean the fuel lines, filters ect....
And,...
Rebuild the carb again...
Reving without a load is Meaningless....

 

[apoc330]

Re: 82 Mercruiser 140 Hesitates and Bogs

Sorry in advance for the book but here is some additional history on the boat.

When I got the boat the first thing I did after ripping out the rotted floor was drain the tank to get the old gas out and just put fresh gas in when I started attempting to take it out this past month. I did not put any enzyme or anything in at that time though just new gas.

I also replaced the fuel pump, filter, pionts, condesor, rotor, cap and wires and my mechanic just put a new fuel line in.

I took it out again today after putting the enzyme treatment in and new spark plugs. It ran better for a few minutes and would actually run up to just over 3000 RPM but did a lot of surging once it got to that point. When I would run at about 2000 RPM she seems to do fine but when I hit the gas it bogs and occasionally surges and starts pinging. I also ran it for a bit with the fuel cap off to make sure it was not a clogged vent.

Any ideas on what else I should check out on the water, could it be compression? I will have my mechanic take a look at the carb again but I dont think he believes me and it doesnt seem like he is able to test it under load. I dont want to keep running it if I am damaging the engine

 

[xxxflhrci]

Re: 82 Mercruiser 140 Hesitates and Bogs

With pinging, the first thing I would check is the timing.

 

[elkhunter338]

Re: 82 Mercruiser 140 Hesitates and Bogs

I agree I would check timing, also have you changed the fuel filter.
Might want to check fuel pressure at the carb. to make sure fuel pressure is adequate. I think you need about 5psi for a carb.
My 140 with a new fuel pump runs about 7 psi, I rejeted my carb because the plugs where sooting up, running to rich. I would look at your plugs after running it to see what they look like too lean or too rich, wrong timing, plugged fuel filter.
If it rev.s good in neutral I would suspect timing or fuel.

 

[apoc330]

Re: 82 Mercruiser 140 Hesitates and Bogs

When i pulled the plugs today, they were pretty black and had a pretty high fuel smell and the third spark plug was a little wet, could it be a choke problem as well maybe dumping too much fuel.

I will take it out this weekend so I can check the timing on the water, I dont think that has been adjusted because I did all of the tune-up but did not mess with the timing. Also would the timing allow it to run good for a while and then all of a sudden start bogging?

 

[apoc330]

Re: 82 Mercruiser 140 Hesitates and Bogs

Latest update:

I pulled the #1 plug and bumped the engine until I felt the compression pushing air out of the opening, I looked at the rotor in the distributor and it looked to be pointing to where I have #1 connected on the cap. When I checked the timing mark, it was no where near TDC it seemed to be about an 1/8th of a turn of the harmonic balancer before TDC.

Am I mistaken or shouldnt the timing mark on the balancer and the TDC mark on the indicator line up on the compression stroke? Will I need to pull the distributor to fix this problem. I have not put the timing light on it yet, wanted to check this first since I could actually check this without taking on the water. And the spark plugs that I just put in yesterday and ran for about half an hour or so were pretty black. I will post some pics later.

Thanks in advance for any suggestions.

 

[fat fanny]

Re: 82 Mercruiser 140 Hesitates and Bogs

Download the manual out of the stickies section for engine I believe it's #13 for the proper timming procedure if you haven't already done so. I wouldn't pull the dizzy unless you have to check timming 1st.

 

[bajuski]

Re: 82 Mercruiser 140 Hesitates and Bogs

"Oh yeah, it has a Rochester 2 barrel carb and I am running on 87 octane unleaded fuel."


My mercruiser 140 manual calls for 89 octane minumum. Since you're running 87 which burns faster than 89, you'll have to retard your spark a little if you plan on running 87 thru it.
Are you sure your point gap is correct after you changed the points? Too little gap and the points open too early causing premature ignition and the pinging results. I always check the dwell after I adjust the points and recheck the engine timing!

 

[Bondo]

Re: 82 Mercruiser 140 Hesitates and Bogs

And the spark plugs that I just put in yesterday and ran for about half an hour or so were pretty black.

Ayuh,... While there's little doubt the timing is probably off abit, because you changed the points,....
It still isn't going to fix a faulty Carb....

 

[apoc330]

Re: 82 Mercruiser 140 Hesitates and Bogs

Thanks everyone for all of the suggestions.

I am going to test the fuel system for leaks using the procedures from one of the stickies and check the timing on the water this weekend I have the manual for this engine.

Do I need any special tools to rebuild a carburetor? Never done it before but really like to understand how this stuff works.

i keep seeing posts about higher octane fuel I will start using higher octane and maybe add some booster to the current tank.

 

[apoc330]

Re: 82 Mercruiser 140 Hesitates and Bogs

Ok, I pulled the carb and realized that my mechanic probably cleaned the carb but did not rebuild it, all of the old gaskets and original accelerator pump were still there but that is another story.

I rebuilt the carb myself and followed the instructions on setting it up. I took the boat out to the lake and made some adjustments on the carb as well as adjusted the timing because it was pretty far off. I am still having pretty much the same issue, runs great when idling out but when I try to accelerate she bogs and then starts to surge and the RPM's never get above 2500 or so. I am using a tach to check RPM's. The boat always starts right up without any effort and never dies. I pulled all of the fuel lines and blew them out as well as the pickup tube in the tank which was really clean.

I was also told that this could be caused by a stuck anti-syphon ball but I am not sure where this would be or how to check it.

Anyone have any ideas?

 

[Bondo]

Re: 82 Mercruiser 140 Hesitates and Bogs

I rebuilt the carb myself and followed the instructions on setting it up. I took the boat out to the lake and made some adjustments on the carb as well as adjusted the timing because it was pretty far off.

Ayuh,... What color are the sparkplugs Now,..??
You had an Overfueling issue before....

You have to diagnose whether the gas is Getting to the carb,..(which it probably is)
Or,..
The Carb can't manage the fuel when it gets it...

What did the carb internals look like,..?? Crudded Up,..?? How'd you Clean it,..??
Outside of an actual Carb Rebuild Shop,....
Kitting a carb is about a 50/50 Shot on old boats....
Sometimes replacement is the answer...

 

[apoc330]

Re: 82 Mercruiser 140 Hesitates and Bogs

The spark plugs actually look pretty good now that I have adjusted the timing and rebuilt the carb, they are a little tan at the ceramic and a black ring around the top couple of threads except for the 4th which has black down almost all of the threads but the center looks good and the strap looks pretty good. I am using NGK plugs and they look like the first picture in this link: http://www.ngksparkplugs.com/tech_support/spark_plugs/faqs/faqread.asp

The carb itself was not very dirty, but the accelerator pump spring looked pretty corroded but alla nd all not too bad.

When I first put the carb back I watched the jets and it seems to be getting fuel just fine and starts right up, idles fine, and in "throttle only" does not seem to have any issues.

 

[apoc330]

Re: 82 Mercruiser 140 Hesitates and Bogs

Here are a couple of pics, sorry for the quality but the best i could do with low batteries on my camera.

 

[ErieRon]

Re: 82 Mercruiser 140 Hesitates and Bogs

Here's a couple of service bulletins that address accelerator bog. It's a 1984 bulletin and may not apply to yours, but it is informative.


http://www.boatfix.com/merc/Bullet/84/84_11.pdf

http://www.boatfix.com/merc/Bullet/84/84_21.pdf

 

[apoc330]

Re: 82 Mercruiser 140 Hesitates and Bogs

Thanks Erieron, unfortunately this seems to apply to the mercarb and I have the Rochester 2GC and just put a brand new accelerator pump on it. Do you need a subscription to get to those service bulletins?

 

[ErieRon]

Re: 82 Mercruiser 140 Hesitates and Bogs

Sorry...it was early

Heres the link to the service bulletins from the sticky "Adults Only" at the top of the page (under Misc. Mercrusier Info.;

http://www.boatfix.com/merc/Bullet/sbcover.pdf