prop size

captgoodwtools · Post by **captgoodwtools** » Mon Oct 27, 2008 1:05 pm

Have a 1973 f-26 trojan sedan with hard top need to match prop w/ new engine was 318 chrysler now has 360 bored to 390. need size and pitch for new engine. old hp was 200 now has 300hp

Paul · Post by **Paul** » Mon Oct 27, 2008 2:52 pm

When the machine shop bored out your 360cid, did they tell you it was 30 over. If so, this means it is .030" larger in diameter on the bore of the cylinders as opposed to 30cid more than the original 360cid.

My F-26 has alot of extras on it and is a very heavy boat. I have a 355cid (350cid .030" over) that generates 300hp. I run in fresh water with a 14 x 9P NiBrAl cupped Michigan propellor. The boat turns 4600 rpm WOT @ 28 mph and cruises in the 3500 rpm range @ 20 mph.

Hope this helps

prowlersfish · Post by **prowlersfish** » Mon Oct 27, 2008 6:59 pm

Captgoodwtools , I would Take the prop you used with the 318 and have about 2" pitch added to it you should be shooting for about 4000-4200 with a 360 chrysler asumeing your runining a stocK cam . what RPM were you getting out of the 318 at WOT and what are you getting out of the 360 at WOT ? are you running 1 to 1 gear and what is the prop size ? with these anssers I should be able to get you closer , but I thing adding pitch to what you have would be a good start .

MattSC · Post by **MattSC** » Mon Oct 27, 2008 7:42 pm

My F-26 has a crusader 5.7 with 330hp, Borg Warner 1:1 and currently have a Michigan Dynajet Nibral 14 x 10 with a full cup. I reach 5100rpm 31knots, and cruise around 3000 rpms gives me about 17-19 kts depending on conditions. Pretty close to what Paul or I am running should put you pretty close, if you have the same transmission ratio. I tried a 14 x 11 ( Obtained the same rpm) without the cup and it was a complete dog! The cup made a huge difference.

prowlersfish · Post by **prowlersfish** » Mon Oct 27, 2008 9:14 pm

Rember the max rpm on a chrysler is a lot lower then a gm

MattSC · Post by **MattSC** » Mon Oct 27, 2008 10:17 pm

Prowlerfish is correct about the gm engines revving higher. I originally had an lm318 and used the same prop, 14 x 10. That was the prop that the boat was shipped from the factory with. I used to get 3900-4000 rpm with it. Another F-26 owner at my marina with a 318 used to run a 14 x 10 cupped propeller as well.