Props and rpm

[balthaus]

As mentioned in a prior post...
Post ignition tune up engines no longer stalled once trannies are engaged.
Had a great afternoon on the river!!!
Once I knew the trannies / ignition were functioning I started to increase RPMs.
All good until 2900 rpm. After approx 2800 ( 20 mph according to iPhone gps speed app) engines would bog and not produce more forward thrust/power.
I think the spare props are 17 x 19 .... But I will have to verify.
Like a dummy I did not check the current props before splashing.
Our seems to be a little odd in the cid / trans ratio dept. and I am not sure what prop would have been stock.
I would prefer fuel efficiency over power / speed.
Any thoughts?

[balthaus]

Or if anyone has any thoughts as to what this prop ratio will produce rpm / power / speed / efficiency wise.
I see that 16 x 16 should have been stock.

[TinLizzy]

I don't know if you did this already, but I would check the timing on the motors and make sure the choke plate is fully open and the 4 barrels are opening up properly. On a different boat I have, mine would bog down when I reached the 4 barrels, they were actually opening up, but I wasn't getting any fuel out of the jets. I filled the carb vents with sea foam and let it sit for a few days and the problem was gone. I also dump sea foam in the vents during lay up to hopefully keep them from gunking up over winter.

[Fastjeff]

I hope those aren't 19 pitch props on there!

Jeff

[Fastjeff]

My 32 footer with the same motors has 17 x 15s and the motors only hit 3,900 rpms WOT (which is fine by me--the boat leaps out of the water).

Jeff

[balthaus]

So, given the specs on our , what would the consensus be for fuel economy but with enough to power to handle the Ohio River currents....if that ratio exists.
I still need to get to her and confirm spare prop size as well as check that all four barrels are putting fuel into the system.

[barkleydave]

16x15 was stock per Marinette site.

17x19 is pretty steep. Too much bite lots of strain on engines.

Should be a nice grove having them
Pitched to 14 or 15 like Jeff s were.

Dave

[newendeavor]

Ben, my 84 Model with 318hp was running best with 14x9 DynaQuad 3 blade cupped. I tried 14x10 also.

[newendeavor]

Correction, 318ci Twins and at WOT 4000 to 4200 RPM. Ran it hard for 10 years with no problems except moisture in Distributor caps and changing impellers every year.

[barkleydave]

14 inch wheels are used on 1:1 transmissions

16 inch wheels are used on 1.5: 1 transmissions

I do not believe he mentioned which gear he had?

dave