5.0 MPI Alpha I Low WOT RPM

[stzanon]

I have a 2004 5.0 MPI merc with an alpha I drive powering an '04 Chaparral 210 ssi. My rpm at WOT is only 4,000 under normal loading conditions (should be 4,600-5,000). I've tried both a 21 and 19 pitch prop, without a noticeable difference. The only thing I can think is that I may be running on 7 cylinders, but I would think this would be detectable and I'm not sure if this engine has an onboard computer diagnostic port.

Any ideas?

 

[Bondo]

Re: 5.0 MPI Alpha I Low WOT RPM

I have a 2004 5.0 MPI merc with an alpha I drive powering an '04 Chaparral 210 ssi. My rpm at WOT is only 4,000 under normal loading conditions (should be 4,600-5,000). I've tried both a 21 and 19 pitch prop, without a noticeable difference. The only thing I can think is that I may be running on 7 cylinders, but I would think this would be detectable and I'm not sure if this engine has an onboard computer diagnostic port.

Any ideas?

Ayuh,... It's a MPI, so, Yes, it's got a 'puter...

Have ya changed the fuel filters,..??

Have ya done a Tune Up,..??

Any service on it,..??

 

[stzanon]

Re: 5.0 MPI Alpha I Low WOT RPM

I just purchased the boat late last fall, so no service other than winterizing/oil change/etc. I will check plug connections tonight, but everything is a bear to get to.

 

[Bondo]

Re: 5.0 MPI Alpha I Low WOT RPM

I just purchased the boat late last fall, so no service other than winterizing/oil change/etc. I will check plug connections tonight, but everything is a bear to get to.

Ayuh,... Welcome to the world of a boat Mechanic...

 

[Don S]

Re: 5.0 MPI Alpha I Low WOT RPM

................. but everything is a bear to get to.

It's a boat, what do you expect.
Pulling the engine to change spark plugs, or water pumps, starters, etc. isn't unheard of.

 

[stzanon]

Re: 5.0 MPI Alpha I Low WOT RPM

It's a boat, what do you expect.
Pulling the engine to change spark plugs, or water pumps, starters, etc. isn't unheard of.

I realize it's not unheard of...just not what I wanted to deal with after just purchasing the boat and it being the middle of a short boating season in NY!

 

[Bondo]

Re: 5.0 MPI Alpha I Low WOT RPM

I realize it's not unheard of...just not what I wanted to deal with after just purchasing the boat and it being the middle of a short boating season in NY!

Ayuh,... Up here in New York, ya buy yer boat in the fall, when the owners don't wanta pay for winterization, 'n storage, for Cheap...

Then take all winter to get it the way ya want it...

 

[stzanon]

Re: 5.0 MPI Alpha I Low WOT RPM

So I had my marina run diagnostics today, and they said there was a defective distributor cap. Apparently the boat had a tuneup at my time of purchase last Fall, and the dealership replaced the cap. Merc apparently had an issue with defective caps hitting some of their distributors. I'm hoping Merc covers the cap cost. This explains why I was running on 6 cylinders and also smelling fuel as two weren't firing. NICE!