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View Full Version : Mercury Tech 2.5 only runs 3800RPM??


PaulR
06-21-2016, 08:39 AM
A buddy of mine picked up a Bad A$$ Allison that was put together back in the mid 1990's so the motor is still running the analog EFI box. Problem is it won't turn over 3800RPM? He replaced the stator and both switch boxes and that didn't help. He also replaced the filters in the fuel system so that's not the problem either. I had an old A15 box sitting around so he tried that and it ran up to 5800RPM before he got out of it so he thought it was fixed. He turned around to make another run and it fell flat at 3800RPM again? He's new to this boat so he was taking it easy.

I have an extra CDI A6 digital box and 56lb regulator so what else has to be done to switch it to digital?

Here are a few pic's

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blowitup
06-21-2016, 01:00 PM
I would try running a new fuel line from tank to motor.Ethanol eats rubber from inside causing lines to collapse.
Michael J Giesler
06-21-2016, 01:23 PM
Did that boat come from Glen Reynolds paul if he is coming to three lakes i can bring my a6 849 box check the fuel pump and regulatory if you need help let me know
PaulR
06-21-2016, 02:23 PM
Mike, no the boat was put together by a local guy that use to race back in the 90's. I think it started out with a 2.4BP that's why it has the old cowl. This is the first time I've seen it in 15 years. Were thinking it could be the TPS so do we just unhook that to run the digital box?
speedstream
06-23-2016, 08:45 PM
Ok,Just to let all know I have replaced the fuel pump,checked or replaced all fuel lines and fittings,but still same result.I think at this time I would be willing to try a15 box as that would be a easy fix to see if this would be the fix rather than changing it over to a digital setup.Fyi also has a new regulator,runs at 35psi fuel pressure at idle,have or 3800 rpm,also hooked up a timing light and it has no interuption of ignition until flywheel stops turning
speedstream
06-23-2016, 08:52 PM
Ok,Just to let all know I have replaced the fuel pump,checked or replaced all fuel lines and fittings,but still same result.I think at this time I would be willing to try a15 box as that would be a easy fix to see if this would be the fix rather than changing it over to a digital setup.Fyi also has a new regulator,runs at 35psi fuel pressure at idle,have or 3800 rpm,also hooked up a timing light and it has no interuption of ignition until flywheel stops turning