Variable RPM issue (stutter)

[thefu]

I have a 20' Glastron Ski/Fish with a 250HP Volvo in it. Last year, everything worked great and I was able to turn like 4500 RPM at WOT and do like 54 MPH. I had it winterized in the fall and this year it now will not go more than 4000-4100 at WOT and every once and a while it will attempt to rev up. The funny thing is, it does it at lower throttle settings as well...you will be putting along at 7mph (and seemingly roughly running) and all of the sudden it will "clean up", rev higher and go about 8.5 mph.<br /><br />I have already run 30+ gallons through it so I don't think its related to the fuel stabilizer.<br /><br />To me it seems like it may not be running on all 8 cylinders due to something in the ignition system.<br /><br />any thoughts from you experts?<br /><br />please help.

 

[lilmandavis]

Re: Variable RPM issue (stutter)

complete tune up make sure its advancing all the time. im working on a 25' glastron and it wont go wide open cause the outdrive bearings are shot. its go the 5.7 gs volvo

 

[thefu]

Re: Variable RPM issue (stutter)

Originally posted by lilmandavis:<br /> complete tune up make sure its advancing all the time. im working on a 25' glastron and it wont go wide open cause the outdrive bearings are shot. its go the 5.7 gs volvo

mine is a 5.7 as well...1998 model...carbuerated.<br /><br />When it was winterized, as part of the service, the shop said they dropped the outdrive and greased the gymbal or some such thing. Could that be part of the issue or caused something?<br /><br />Also, like I said, it happens on all RPM levels, its almost like there is 85-90% of the power 75% of the time and then once and a while it will "kick in" with additional revs without me advancing the throttle.<br /><br />For a tune up, is that something I could take on. I have tuned up and adjusted timing on many an automotive engine...other than the plugs and wires and confirming the timing, what else is there?<br /><br />Finally, it just seems strange that it went into storage fine, came out of storage and started right up and runs great except for this issue...could something as simple as a fouled plug or plug wire manifest itself in this type of symptom?

 

[ron7000]

Re: Variable RPM issue (stutter)

sounds like water in the fuel and dirty carb. I went thru this with mine last year. I had it running great the season before, winterized it and used stabil in the gas but first time out it would die at idle and wouldn't even get up on plane. I was pissed because I had put a lot of work into it the season before and it was running super. Pulled the carb off, couldn't believe the scale and rust spots in the bowl. I attribute it to ethanol in the fuel absorbing moisture. While anything's possible, I think from your description it's the carb.

 

[Bondo]

Re: Variable RPM issue (stutter)

While anything's possible, I think from your description it's the carb.

Ayuh,......... Me Too.........

 

[thefu]

Re: Variable RPM issue (stutter)

i knew i should have bought an EFI!<br /><br />There goes another $500...

 

[bruceb58]

Re: Variable RPM issue (stutter)

Originally posted by TheFu:<br /> i knew i should have bought an EFI!<br /><br />

And why would you say that? Carbs are a lot cheaper to fix than EFI!

 

[thefu]

Re: Variable RPM issue (stutter)

Well, efi wouldn't have this problem and it would run consistently when i want to go to strawberry reservoir at 9000 feet as well as lake mead at 2000.<br /><br />But I get what your saying, if my fuels system goes kaput, a new carb is far cheaper than the efi computer, fuel rails and injectors, etc.

 

[fendersfender]

Re: Variable RPM issue (stutter)

ummm....try the tune-up before replacing the carb....if the engine was fogged last fall, it might just be fouled plugs

 

[bruceb58]

Re: Variable RPM issue (stutter)

I understnad what you are saying, I have a carb in my 1997 Volvo and always say the same thing when I am on Lake Tahoe. <br /><br />If you had EFI you may have a whole different set of problems and you would be wishing you had the simpler carb.

 

[thefu]

Re: Variable RPM issue (stutter)

I am sure it was fogged so that could be the issue...and since i just bought this last year I have no idea how long they have been in there.<br /><br />ok, so plugs i can do pretty easily and since i have no idea when they were done last its probably a good idea. What are the recommendations for plug type/brand? I have seen nippon denso and ngk recommended here.<br /><br />I will do that before I take it out next time and see where it gets me.