Not enough engine?

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   Well, I just tested my newly acquired and freshly rebuilt O.J. 3-blade prop on my '68 mustang (with a Ford 289 cid engine and 2-barrel carburetor). The O.J. prop is a 12" x 13, cupped, which is the same as the original prop it replaced.

Top engine revs dropped from 4000 to 3000 and the boat is much slower (I have no speedometer). This is a huge difference. 

Is this just too much prop for my engine?  

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Jim_In_Houston Members Profile Send Private Message Find Members Posts Visit Members Homepage Add to Buddy List Platinum Member Joined: September-06-2004 Location: United States Status: Offline Points: 1120	Post Options Post Reply Quote Jim_In_Houston Report Post Thanks(0) Quote Reply Topic: Not enough engine? Posted: September-21-2004 at 2:10am
	Well, I just tested my newly acquired and freshly rebuilt O.J. 3-blade prop on my '68 mustang (with a Ford 289 cid engine and 2-barrel carburetor). The O.J. prop is a 12" x 13, cupped, which is the same as the original prop it replaced. Top engine revs dropped from 4000 to 3000 and the boat is much slower (I have no speedometer). This is a huge difference. Is this just too much prop for my engine?

79nautique Members Profile Send Private Message Find Members Posts Add to Buddy List Grand Poobah Joined: January-27-2004 Location: United States Status: Offline Points: 7872	Post Options Post Reply Quote 79nautique Report Post Thanks(0) Quote Reply Posted: September-21-2004 at 3:46pm
	Way to much prop your rpm need to be around 4200-4500. you could put on a four barrel intake and carb and get a little more power to help out with the prop you have. but i would try a 12x12 un-cupped prop with your current set-up

Tim D Members Profile Send Private Message Find Members Posts Add to Buddy List Grand Poobah Joined: August-23-2004 Location: United States Status: Offline Points: 2641	Post Options Post Reply Quote Tim D Report Post Thanks(0) Quote Reply Posted: September-21-2004 at 4:25pm
	My 1966 Mustang has a 12x12 prop. I have a spare 12x14 but I've never tried it out.I know it would affect acceleration, but would add a mile or two on top end. One day I'm going to put it on, probably when I get the 12x12 redone and see what difference it makes. What prop did you have before?
	Tim D

Jim_In_Houston Members Profile Send Private Message Find Members Posts Visit Members Homepage Add to Buddy List Platinum Member Joined: September-06-2004 Location: United States Status: Offline Points: 1120	Post Options Post Reply Quote Jim_In_Houston Report Post Thanks(0) Quote Reply Posted: September-21-2004 at 5:05pm
	The prop I pulled off (for repair) was also a 12 x 13 with small cups. The new prop (not really new) is also a 12 x 13 but it seems to have a lot more surface area, larger cups, and the blades are "raked" towards the rudder. The old prop seems to be flatter, if that makes sense. I don;t know the make of the old prop. I'll know tomorrow when I retrieve it from the prop shop. Maybe I should kick down to a 12 x 12 (unless I can gain some HP from my 289 without breaking the bank.) Any thoughts? (So how are these prop cups sized anyway? A,B,C and Double D?

Jim_In_Houston Members Profile Send Private Message Find Members Posts Visit Members Homepage Add to Buddy List Platinum Member Joined: September-06-2004 Location: United States Status: Offline Points: 1120	Post Options Post Reply Quote Jim_In_Houston Report Post Thanks(0) Quote Reply Posted: September-21-2004 at 5:07pm
	Anyone want to recommend a small 4-barrel carb for a '68 Ford 289?

882001 Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: October-21-2003 Location: United States Status: Offline Points: 332	Post Options Post Reply Quote 882001 Report Post Thanks(0) Quote Reply Posted: September-21-2004 at 6:06pm
	im just swaping from a stock13x13 michigan wheel to an acme 13x 11-1/2. so all that surface and cupping must make a huge difference. i havent recieved it yet but ill let you know. try www.skidim.com on the intake and carburator
	kemah texas 1988 skinautique "2001"

boat doctor Members Profile Send Private Message Find Members Posts Add to Buddy List Newbie Joined: June-28-2004 Location: United States Status: Offline Points: 29	Post Options Post Reply Quote boat doctor Report Post Thanks(0) Quote Reply Posted: September-23-2004 at 7:26pm
	recently found some extra ponies in my 302, now pulling a 13x13 oj 4 blade 4500 . the trick to my added power was as follows. edl-1409 edelbrock 600 cfm marine carb. edl-2121 performer intake mallory unilite conversion,no more points high output coil,400 in gear idle fpp-1250 intake gaskset sum-g1579hs s/s intake bolt set these mods gave me a lot more hp,now to add a set of GT 40 heads,should give you 40 hp and 400 rpms. the best bang for your buck. my 1964 am. skier now roars rather than growls. all part #s are from summit racing good luck
	boatdr

79nautique Members Profile Send Private Message Find Members Posts Add to Buddy List Grand Poobah Joined: January-27-2004 Location: United States Status: Offline Points: 7872	Post Options Post Reply Quote 79nautique Report Post Thanks(0) Quote Reply Posted: September-24-2004 at 4:45pm
	You can spend about 300-500 and replace the intake and carb and convert it to electronic pointlees ign. and gain a lot of HP. The intake and conv. kit will run around 250 loo at this carb on e-bay and you might be able to pick it up pretty cheap but I would rebuild it to be safe this is the item number on e-bay 2490931707. The way you descriped your prop it sounds like it has a ton of cup to it and that is what is killing your RPM a 12 x 12 prop is what it came with from the factory. Check your compression first and make sure your not getting some blow by because if you are then you realy don't want to increase the HP without a re-build of the motor and if it is a little low on the compression then that would effect the low RPM as well.

reidp Members Profile Send Private Message Find Members Posts Add to Buddy List Platinum Member Joined: December-06-2003 Location: Mooresville, NC Status: Offline Points: 1804	Post Options Post Reply Quote reidp Report Post Thanks(0) Quote Reply Posted: September-26-2004 at 3:03pm
	Jim, From what I've found on actual prop tests, the 12x13 OJ IS NOT a direct replacement for your 12x13 Federal/Michigan prop, but more comparible to a 12x14 Fed. You will loose rpm and speed. With the rake of the OJ prop, notice how the blades slope aft when looking at prop from side, they effectively have more blade area for the same diameter and pitch. I need to pull the prop book out again for a refresher. So if OJ will re-pitch it to 12x12 you may be fine. Plus keep in mind that with your pending engine upgrades, you'll be able to turn it better. Tim D, Try that 12x14, but dollars to donuts says it will run slower top end than your 12x12. Your engine won't turn the needed rpms to get that speed out of it, just like many autos run faster top end in 4th or 5th gear (1:1) than they will in their respective overdrive gears.
	ReidP 1973 Mustang

Jim_In_Houston Members Profile Send Private Message Find Members Posts Visit Members Homepage Add to Buddy List Platinum Member Joined: September-06-2004 Location: United States Status: Offline Points: 1120	Post Options Post Reply Quote Jim_In_Houston Report Post Thanks(0) Quote Reply Posted: September-26-2004 at 9:00pm
	The original prop is a 12 x 12 as is the OJ prop. You are very correct. The OJ prop is raked way towards the rudder - a lot!!!! My 289 just can't produce enough torque right now to turn it. So the moral here is a 12 x 12 is not always a 12 x 12. Thanks for the insight. Maybe after I make a few changes to the engine it will turn it - I'll let you know.

Not enough engine?

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