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JT 671 TIB Idle Speed

"I have a pair of 671 TIBs in

"I have a pair of 671 TIBs in a 44' Ocean Sportfish. They idle at 650 rpms, but this seems slightly high. Any insight would be appreciated."
 
"We have the same engines in o

"We have the same engines in our uniflite and they idle at about 650 seems high, but when we lower it the engine coughs alot and starts real slow!"
 
Thanks Todd...I have not tried

Thanks Todd...I have not tried lowering the idle yet to see the result. I have 1.5:1 Capital gears so I guess they can handle the torque at 650 rpms..will probably have my Detroit mechanic on board soon anyway
 
Re: Thanks Todd...I have not tried

Thanks Todd...I have not tried lowering the idle yet to see the result. I have 1.5:1 Capital gears so I guess they can handle the torque at 650 rpms..will probably have my Detroit mechanic on board soon anyway

I have similar issue. The tags on my governors on my 6-71 Detroit engines say that the idle speed is between 500-900rpm.
These governors are SWVS (single weight variable speed), and I really would love to see them set at 500 because this 42 foot Uniflite is quite fast even at low idle which means I have to constantly engage and disengage the Twin Disc transmissions when backing into my slip or maneuvering in close quarters.
There seems to be a lot of this and that out there, but I haven't really found anything substantial that explains the "how to" in sufficient detail.
I know the governors are touchy business that need finesse, but even then, it's not easy to find an experienced mechanic to guide me, so I would like to know what you find out about this issue.
Thanks,
jim
 
Hi guys. The problem with dropping your idle speed is governor droop. (rpm difference between neutral and in gear which is about 100rpm}. Dropping idle to 550 may cause hard starting and is so close to min. Gov speed could stall or surge. Stay at 650rpm. Also capitol ,zf and twin disc have a trolling valve which allows the trans to slip in gear at idle so that the prop turns slower.
I tried the first capital gear trolling valve on my 8v92ti's with capitol 1.5:1 back in 1984. Worked excellent
charlie w.
 
Ours idle at 550 no load, twin disc 507's I believe. There is no drop in RPM when it goes in gear, if anything they pop up to 600 or so under load.
 
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