Sears 15hp issues

I have a 1976 15 hp Sears outboard model# 217/58631-1 that is will run rough and then will backfire through the carb. If i work the choke I can keep it running when it does this. I am wondering if this is due to a lean fuel situation or if it may have something to do with the ignition... anyone experienced this or have ideas?

Thanks.

Re: Sears 15hp issues

If choking it helps I say you need a carb rebuild, you could have a slit or hole in the fuel pump element, do you know the engine model number? should read BV 1500 38X abc on a metal tag, some models had an external pump and some had the duck bill pump element.
I'm not sure but I think CPC will have the external pump diaphram.
Also I think its reasonable to rebuild the SSI on these old engines before that becomes a issue and it could very well be part of your problem. Its to easy not to rebuild it. If you join the yahoo group everything you need to know about cap replacment is there.

Re: Sears 15hp issues

Thanks mrcrabs - I plan on rebuilding the carb and pump tonight. Hopefully that takes care of the issue. I agree that rebuilding the SSI is a good idea, seems to have solid spark but wondered if the timing might be affected somehow. I am under the gun trying to get this motor working for the weekend. I will certainly look at doing that as well.

Re: Sears 15hp issues

Yes I meant to mention the timing and if you just bought it theres a chance its been tinkered with but theres not allot of movement to the stator adjustment and a middle of the road setting should give you a running motor, maybe you can tell where screws have been from witness marks. The timing procedure is a two tool setup, one to measure the trigger at full advance and transferring that measurement to the stator with another gauge. If you have to buy a set you will pay double for each tool on Ebay, I bought mine ( both of them) from http://www.rcpw.com/ for 28$ shipped.

I will be in dry dock for a week or so but I uploaded the timing procedure in the picture section of the yahoo group, you will have to save them to your computer to inlarge them to read.


Later mates, catch you all you on the second whistle

Re: Sears 15hp issues

Hi, I had a similar issue with a 7.5 ,one of the reed valves was cracked and would pop back through carb and run rough under load but would clear up when I choked it some ,ran fine in the test tank . just a thought

Re: Sears 15hp issues

no reeds in the twin, they use a rotory valve.