1974 OMC 165 HP Optimal RPM @ WOT

[utadventure]

Still learning about the '74 Cobalt we bought. It has a 165 hp, 6 cyl, 2 brl with OMC Cobra Stringer outdrive.

Top RPM on the lake earlier this week was 3800 rpm @ WOT. What should the ideal max. rpm be? Seems low to me.

Dave

 

[HT32BSX115]

Re: 1974 OMC 165 HP Optimal RPM @ WOT

Still learning about the '74 Cobalt we bought. It has a 165 hp, 6 cyl, 2 brl with OMC Cobra Stringer outdrive.

Top RPM on the lake earlier this week was 3800 rpm @ WOT. What should the ideal max. rpm be? Seems low to me.

Dave

Howdy Dave,


Most of the I-6's had a WOT RPM of around 4300 RPM. If you're only doing 3800 PRM the engine could be just tired or there's other things that would make a difference.

Check out the "Adults Only" Sticky, #13 in the list.


Regards,


Rick

 

[utadventure]

Re: 1974 OMC 165 HP Optimal RPM @ WOT

Wonderful reference, thank you.

We've been working on many of the things on the list. The prop on the boat is a 14 X 15p. There is a spare prop on the boat (13 X 14p) that I'm taking in to be repaired and then I'm going to try it again.

The PO had done a tune up (plugs, points, rotor, cap and carb rebuild). I'll be adding fresh fuel (and seafoam) to the tank before the next outing. I also corrected the dwell on the points from 24 to 17 (16-19 is spec). I leaned out the carb a little. The combination seems to improve the hesitation/dieing when accelerating tremendously.

Dave

 

[HT32BSX115]

Re: 1974 OMC 165 HP Optimal RPM @ WOT

Ok,

Sounds like you're on the way to getting it running well. I would leave the Seafoam out of the gas though. I have never understood why people think Naphtha mixed with light oil improves running in a gasoline engine.

Good luck,


Rick

 

[Fordiesel69]

Re: 1974 OMC 165 HP Optimal RPM @ WOT

Pull the distributor and inspect. The springs in the advance unit seem to get fatigued, and also the bushings near the gear can get sloppy.

 

[utadventure]

Re: 1974 OMC 165 HP Optimal RPM @ WOT

Got the boat in the water again today. I had the 14 X 14p prop repaired this week and used it today. WOT topped out at 4500 rpm. Cruised around Utah Lake at 4000 rpm without hesitation.

After a while we stopped and just rested for about 30-40 min. It acted flooded but started with the throttle wide open..... that's an issue for another day.

Now the trailer needs some attention.