Help!!please!! merc 3.7 backfires and won't accelerate

[jt2004]

I have a 1987 four winns horizon with a 165 mercruiser (I know I know) and I have tuned it up, put a carb kit on, checked the timing, replaced the fuel filters, and I am still having the same problem. Starts great, Runs Great, great wot. the problem occurs from about 1000 rpm -2000 rpm when I go to accelerate I get a decrease in rpm and it will backfire and stall if I do not return the engine to idle in time. Then if I try it again it will give me a hole shot and accelerate smoothly. Also as it get warm its ability to idle goes away and and I get about 30 good seconds of idle and then it will become erratic and stalls. Any Ideas?? Fuel vaporization? Shot Carb? fuel pump?check valve? all ideas I have toyed around with.
John

 

[Bondo]

Re: Help!!please!! merc 3.7 backfires and won't accelerate

Shot Carb?

Ayuh,... That's My guess...

 

[jt2004]

Re: Help!!please!! merc 3.7 backfires and won't accelerate

Thanks Bond-o that is what I was looking towards as the most likely cause. Another question do I just stick with a 2 or go to a 4.

 

[zbnutcase]

Re: Help!!please!! merc 3.7 backfires and won't accelerate

Stick with 2bbl, I'd do a Holley 500cfm marine carb with adapter.

 

[jt2004]

Re: Help!!please!! merc 3.7 backfires and won't accelerate

Thanks for the Advice, as a follow up I think I have found my problem!! The fuel hose was rotted and the last owner must have replaced the fuel barb and check valve with the wrong size. Not only was the flow restricted but the system was getting air bubbles from the rotten end right there at the fuel barb. $20.00 fix