6CTA, underpropped or not making power?

[dnord2]

First post, I’ve been through these forums for a while. I have a 97 Formula 41PC with 450’s. Currently, only turning 2500 RPM WOT and 2900 high idle. I recently messed with the throttle linkage, since there was some extra in there but still not giving me the proper RPM. I’m ok with getting props pitched, but initially I want to make sure the motors are making proper power so I’m not just band-aiding a possible problem with engines. I have installed the SBMar boost/egt gauges and at WOT 2500 RPM I’m seeing about 28 PSI and 900egt. Engines have 750 hours on them, both water and air sides have been cleaned/serviced/replaced top to bottom. Temps run 170/180. Thanks in advance-

Topic

[dnord2]

ok, thanks! Props it is!

[Tony Athens]

Your high idle is right in PERFECT spec if your tachs are accurate..(2920-3020–page 2 of the attached) Nothing to adjust..

Tony

[dnord2]

Thanks Tony, I expected that response lol. Following all your tips and tricks, even your advice is to make sure the engines are running properly before re propping. I’m totally ok with, Im just covering all the bases.

And back to my original question, is there a way to adjust high idle or just leave it. Im on the low side of your recommended normal. Re pitching my props 2″ isn’t going to help my boat in neutral lol

Thanks for the help-

[Tony Athens]

If you are making 28 PSI boost, your engines are trying to making full power, but are are struggling because you need to pitch down a solid 2″……….. Real simple–You are over propped.. Quit chasing something that is not there as you won’t find it……………………………………..ACCEPT and get it over with, and it with then all come together..

Tony

[dnord2]

I haven’t plotted boost/egt, but gets on plane no sweat. I think there is less drama than I originally thought. I went out yesterday and got some tach verification and readings. Looks like WOT RPM is about 2580, not ideal but better than I thought it was.

Can high idle be adjusted? I’m only at 2900, MAYBE 2900 might be more like 28 something. I see there is a high idle adjustment screw on the linkage, can you turn that up?

Thanks in advance-

[Scotth]

Some googling results shows 28-30 psi @ 2600 RPM. Have you plotted PSI and EGT versus RPM? Does it get on plane easily?

[dnord2]

So, can anyone tell me what normal boost readings should be on a 6CTA? Mine are at 28 psi

[dnord2]

Ive owned the boat for a year, not sure of its previous history. I guess what I’m looking for is what people are getting for boost at 2700 rpm. thx-

[donald roth]

Your boat is a ‘97, has it always been unable to make rated rpm, or is this something that happened recently or gradually?
If everything else is good as you say it is, it’s definately overpropped.

[dnord2]

No smoke, all the filters have been changed. The other day, I started digging into the throttle stop since they weren’t going to the stop with slight spring pressure. I though that might have been the problem, but that didnt help. If it did help, it wasn’t much. 2500 is all Im seeing out of both motors. 2 people, half tanks.

[donald roth]

Got smoke?
If so, what color?
Air/fuel filters clean?
Are you certain that the cables are allowing the throttle to travel to the high stops?
It’s certainly possible that it’s overpropped, but check all the simple stuff first!

[Author]

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