Anyone tried a 3 hole accelerator arm on Mercarb?

[iammarcuse]

I notice lots of posts on 3.0 Mercruisers bogging on acceleration. I don't see a lot of posts where they figured it out. Like many, my 1991 is doing the same. It is new to me and I have not yet water tested it as it was not even running well on the hose despite new points and plugs. I rebuilt and cleaned the Mercarb and set everything to spec. That got me starting and idling very well. However it still stalled if I hammered the throttle. I checked the timing. It was at only 2 BTDC. (Points type distributor) I reset it to 8 BTDC. That made a significant improvement but still bogging. It seemed to me that the accelerator pump shot in an awful lot of fuel. I bent the pump arm linkage to give me the shortest throw possible and the bogging almost disappeared...but not quite. It will still backfire on occasion. I don't like that at all.
I found this link about a 3 holed accelertor arm http://www.marineengine.com/discus/messages/12486/97_08-84745.pdf Anyone tried one? And what kind of results? (I cannot find a part number for it on line). Or maybe I'm on the wrong track completely...any other suggestions to fix the problem?

 

[cbelgum]

Re: Anyone tried a 3 hole accelerator arm on Mercarb?

A coulpe of things in your post caught my eye; you say you have not tested it on the water - it is the only place you can really test it. Reason being the engine setup is designed to have back pressure (load) from the prop against the water. If you don't have the back pressure you could potentially do damage to the engine because it is not under load, you have no idea if it actually will accelerate or bog down when you try it on the trailer with muffs. Put it on the lake and try again. Once she is warmed up and idling nicely, find a clear water area where you can let her drift while you work and try again to adjust the carb. That way you can fine tune it to get the best idle, and the best pick up on acceleration. You may find you need to undo the work you did on the muffs, particularly bending the arm too much. The engine does need a quick shot of gas to accelerate quickly. Second point is that you gunned it on the muffs - this is an absolute no-no! Never go over about 1500rpm - the hose can't feed enough cooling water to the engine and you will overheat or worse. As above - back to the lake! Had to do much the same with my 4.3 V6 when I got it too, and being out on the lake in a lot of free sapce was really convenient. Good luck.

 

[iammarcuse]

Re: Anyone tried a 3 hole accelerator arm on Mercarb?

Alright, I'll give it a go. I wanted to sort out the major issues before I water tested. Thanks.