1997 115 SPL misses at idle

[Bushleaguer]

After doing a fuel tank replacement in my boat, I fired up the motor and it started up as it does every spring. Problem is that at idle, every 15 seconds or so, the motor "pops". When on the muffs, you see a large puff of smoke out the prop hub when it happens. Sometimes, it coughs so hard, the motor dies. It fires right back up. I would call it a miss I guess.

I put it in a test tank rather than the muffs, and it does the same thing. I tried a decarb and new plugs, still the same thing. Have new Racor seperator filter installed.

Am I looking at some sort of ignition problem here, or a fuel problem?

I have new fuel hoses below deck, but will try new hoses from the bulkhead to the filter and from the filter to the engine with new primer bulb. What else can I check for?

 

[CharlieB]

Re: 1997 115 SPL misses at idle

A lean idle on one or more cyl's causes a 'cough'

I suspect the idle air bleeds are dirty and restricted causing a lack of fuel through the idle circuit.

You could shortcut and see if the spray tube on a can of carb cleaner will blow through the idle air bleeds, but the ideal method is to thoroughly disassemble, clean and blow out every surface, passage and jet.

Chemical fixes are not near as reliable as doing the job right the first time.

 

[tashasdaddy]

Re: 1997 115 SPL misses at idle

agree carb cleaning an rebuild, remove the jets. special tool

 

[Bushleaguer]

Re: 1997 115 SPL misses at idle

Thanks guys. I'll rebuild and post results.

 

[Bushleaguer]

Re: 1997 115 SPL misses at idle

One more ??

Can I pull the carbs, re-work them, and re-install and run it, or do I have to link n synch??

 

[ezeke]

Re: 1997 115 SPL misses at idle

Fuel restriction in the carburetors as stated could be the problem, but extra air getting in is just as often, if not more often, the cause of running lean. Re-check all of your connections on the fuel system, then put a little steady pressure on the primer bulb while you check the fuel system all the way to the carburetors for signs of a leak.

Check the gaskets between the carburetors and the intake manifold and make sure that the check valve lines are tight.

 

[tashasdaddy]

Re: 1997 115 SPL misses at idle

if you are careful, you don't have to link n sinc.

 

[Bushleaguer]

Re: 1997 115 SPL misses at idle

Thanks again guys.

 

[Bushleaguer]

Re: 1997 115 SPL misses at idle

It was the carbs. Thanks for all the help.