2003 Merc 115 - engine miss

[mojeep]

Got this in the wrong category on my first try so I'm reposting it! <br />I have a 2003 Merc 115, 2-stroke, non-EFI model. It has a sporadic engine miss across most of the RPM band. However, it rarely misses when at full throttle (5000-5100 rpm). I suspect a defective CDM/coil pack based on past problems with another Mercury. Is there a way I can test these? <br />Also, my fuel economy is less than ideal. Is this related to my ignition problem or is this motor just on OPEC'c Top Ten Favorites list?

 

[achris]

Re: 2003 Merc 115 - engine miss

The miss is more likely a stator problem. Merc dealers have a CDM tester (or should).<br /><br />

Also, my fuel economy is less than ideal

Define.<br /><br />Chris.........

 

[mojeep]

Re: 2003 Merc 115 - engine miss

I cruised about 1 hour at 3/4 throttle and used about 10-12 gals of gas

 

[achris]

Re: 2003 Merc 115 - engine miss

Mojeep,<br /><br />We need to know a few things.<br /><br />1) What size boat is it on?<br />2) What size prop are you running?<br />3) What are the rpm at full throttle?<br />4) What speeds are 3/4 throttle and full throttle?<br /><br />Generally though, that sounds in the ball park.<br /><br />Chris.............

 

[mojeep]

Re: 2003 Merc 115 - engine miss

1) 18.5 ft bass boat<br /><br />2) 3 blade stainless - 20P Merc Laser<br /><br />3) 5000 RPM at full throttle, 3500-4000 at 3/4<br /><br />4) 3/4=30-35 mph, full=47-48 mph<br /><br />I'm comparing my fuel economy to a friend's Merc 150 EFI on a similar bass boat. He seems to use about 10-20% less fuel to run the same as I do. Does the EFI make that much diff?<br /><br />Thanks!

 

[achris]

Re: 2003 Merc 115 - engine miss

Does the EFI make that much diff?

Yep!