Another prop thread

[mapleleaf]

I need to replace my OJ 803 14" X 16 cup prop. It maybe repairable, but most likely only as a back up prop. Willing to sacrifice some top end for torque. Any recommendations??? Boat's a '90 Conbrio.....

[DAFF]

What was the top end like with that prop. My 13-13 had a good hole shot and maxed out about 43mph... I was thinking to add some pitch and get allitle more top end. But if it only gives 2-3 mph than I will stick to the old 13-13 and get a 4 blade...

[mapleleaf]

with my new Pitot's this year she'd play between 47 and 52 mph. I think it varied cause I was messing with the wake plate. I think next year I'm looking for holeshot...... And don't worry about the rudder, looks like I'm buying a new one or sitting on dry land!!!!!!

[jet]

14x14x.105= HOLD THE F#*K ON!! 1700 lbs to plane and 21 mph in 3-boat lengths. Its a NITRO boat now. lol. Me ole 3- blade took 10 mins to get it up to speed and plane. Jet

[firstdogriver]

I had a three blade OJ 14 X 18 on my 89 Conbrio. I topped out at about 39-40 mph (GPS) At about 4100 rpms. I went to a four blade ACME 14 x 15.5 105 cup. My hole shot was greatly improved. My top speed increase to 43 mph. However my Max RPMs dropped to 3900. Now I'm toying with the idea of a high flow intake, GT40 heads and 650-700 cfm Holly.

1989 Conbrio
351 Windsor
1:1.23 transmission

[jet]

firstdogriver..why? these boats are tractors not race cars. I use to look for performance also..but once you put a big prop on it it still goes 40 mph, it has ALL the push you need..put your money somewhere else. .02

[DAFF]

Hey Jet... What rpms are you hitting at wot???

I think the idea of higher pitch props and top speed is greatly dependent on the HP of the boat. Because of the trans gearing firstdogriver engine cant develope enough hp to get full use of his power band. I am sure at 3900 the engine is maxed out and not running at its full potential. Think of a moutain bike going up hill in the wrong gear. You are working like mad and bearly moving ..... Too much gear!!

There must be a formula where all the knowns and unknowns can be entered to give you the perfectprop.

[firstdogriver]

I had a three blade OJ 14 X 18 on my 89 Conbrio. I topped out at about 39-40 mph (GPS) At about 4100 rpms. I went to a four blade ACME 14 x 15.5 105 cup. My hole shot was greatly improved. My top speed increase to 43 mph. However my Max RPMs dropped to 3900. Now I'm toying with the idea of a high flow intake, GT40 heads and 650-700 cfm Holly.

1989 Conbrio
351 Windsor
1:1.23 transmission

[jet]

Not sure, havent WOT her in years. I only have to use 20-40% throttle now..no need to lay into her anymore..and rarely reach 30 mph.

Intake- $350
GT40- $500
700cfm $400 =$1250 0-45 mph=.5 secs faster??
Not worth it..now drop $1250 in your interior or stereo or more toys..Priceless. : )

[87SunSportMikeyD]

Call Jason or JT :)

[ejojprop]

I had a three blade OJ 14 X 18 on my 89 Conbrio. I topped out at about 39-40 mph (GPS) At about 4100 rpms. I went to a four blade ACME 14 x 15.5 105 cup. My hole shot was greatly improved. My top speed increase to 43 mph. However my Max RPMs dropped to 3900. Now I'm toying with the idea of a high flow intake, GT40 heads and 650-700 cfm Holly.

1989 Conbrio
351 Windsor
1:1.23 transmission

Neither size is correct for a boat with the 1.23:1 transmission. Feel free to give me a call to talk about what the correct size should be for your application.

Eric

[87SunSportMikeyD]

I love it when the experts come on to answer. For some reason I find props very interesting. I would actually love to be trained to be a prop sales person lol! Imagine all the internet sales I could make! :)

[DKJBama92Mariah]

Neither size is correct for a boat with the 1.23:1 transmission. Feel free to give me a call to talk about what the correct size should be for your application.

Eric

Eric is spot on here. Considering he builds props for these boats for a living, you would do well to heed his advice. If your WOT RPMs are only 3900, you are overpropped by a significant amount. Running too much pitch like that is very hard on the motor.

Eric set me up with an OJ 13x15.5 4-blade CNC wheel for my Mariah/1.23/GT40 combo a few years ago and I have been completely satisfied. I lost almost no top end, yet the boat hops on plane significantly faster. I will caveat however that I do not run ballast in my boat, but getting on plane with a full load of 8 people in the boat is still not a problem.

Granted these are not speedboats, but having the ability to run 48mph to shelter when a fast thunderhead approaches is quite comforting.

Regardless of whether you prefer an OJ or an ACME wheel, the manufacturer is in the best position to recommend a prop for your particular application.

[mapleleaf]

Neither size is correct for a boat with the 1.23:1 transmission. Feel free to give me a call to talk about what the correct size should be for your application.

Eric

Please eloborate, I'm going to have to get myself a new prop before next season and am looking for what Derek described, top end and torque or the best combo of the 2. I would love to say I am going to be running a ton of weight in my boat, but its an open bow comp, who am I kidding???
And we do still use it for skiing from time to time...

[DKJBama92Mariah]

Please eloborate, I'm going to have to get myself a new prop before next season and am looking for what Derek described, top end and torque or the best combo of the 2. I would love to say I am going to be running a ton of weight in my boat, but its an open bow comp, who am I kidding???
And we do still use it for skiing from time to time...

Mapleleaf,
Just call him at 865-458-5205

It will go quicker over the phone. If Eric tried to type out responses to everyone's prop questions, he'd have little time left over to run his factory.

On a side note. Definitely go with a 4-blade CNC prop. They run smoother because they are inherently easier to balance than a 3-blade. Like yours, mine came with an OJ Legend 3-blade 14x16RH with cup. The boat was sluggish out of the hole with more than a few people on board and ran 47 or so mph at 4200 rpms. With brand new underwater running gear and the new CNC 4-blade prop, my Mariah felt like like a completely different boat. WOT yielded 47-48mph at 4400rpm.Butter smooth is the only way I can describe it, ZERO hull vibration at any speed; BMW 7-series smooth, but with enough stump-pullin torque to drag my big 245lb butt out of the water in a slalom deep-water start.

The 4 blade also handles much better around the dock; MUCH more control. This summer, while running with my 3-blade spare, I bumped a dock much harder than I intended because I didn't have the level of control I was used to. With the 4-blade it takes less throttle to stop the drifting boat or to scoot the stern around 180 degrees in tight quarters. Being able to do these maneuvers at 550 or 600rpm as opposed to at 800rpm is a major advantage as the boats movement is slower and maneuvering is much more controlled.

[mapleleaf]

thanks D I'll call him, on a lighter note I guess you're assuming I can get my boat to run at 5-650 rpm at the dock!!!! My carb's so fussy even after 2 rebuild's that a small change in the weather and I'm messing with it. Did however manage to find the sweet spot with my idol most days out, with my Leatherman.....

[DKJBama92Mariah]

thanks D I'll call him, on a lighter note I guess you're assuming I can get my boat to run at 5-650 rpm at the dock!!!! My carb's so fussy even after 2 rebuild's that a small change in the weather and I'm messing with it. Did however manage to find the sweet spot with my idol most days out, with my Leatherman.....

Hmmmm, idle should be set at 600 rpms with the transmission IN GEAR. When in neutral it will run 650-700. With the engine in good tune, 600rpm in gear should be easily doable. I have mine set for about 550 in gear with no problems except a little coughing on a cold start in cool weather. 500 in gear is pretty much a no-go; it barely stays running and the damper plate makes a horrid racket.

I took a holeshot video today with the camera on my phone. The sound quality is terrible, but it should give you an idea of the acceleration characteristics of a 4 blade sized for general purpose use. Click the picture to see the video

http://img.photobucket.com/albums/v55/dkjpika/Boat/th_VID_20101030_153808.jpg (http://smg.photobucket.com/albums/v55/dkjpika/Boat/?action=view&current=VID_20101030_153808.mp4)

This video is with the prop in far from perfect shape. I hit a large snag going way too fast earlier in the summer. I had it repaired by a shop over in Mississippi because my regular local prop guy is down on his back, and they did a less than perfect job. It's vibrating just enough to make me uncomfortable running it long term. When I haul out for the winter I'm going to send the prop back to Eric to see if they can pound it back into shape. It may be destined for the scrapheap though.

[mapleleaf]

I should"ve been a little more specific. My tach has been cacked since I bought the boat, so when we tuned the carb the mech. did it with his own reader and he thought he had the idle at between 7-800. Where I would run into trouble, mostly in the hot, humid dead of summer, was when I wanted to be in gear at idle speed. because those rpm's are lower (probably just as you mentioned) it would sputter and die. It would take some tweaking on the idle screw to get it idling in gear. Oddly enough, in the spring and fall she runs like a top without any fool'in around.
I will be replacing my tach in the off season, tried to use a used tach off dshaff's '86 SS, but all the wiring pickup's are diff. My tach has what looks a volume control knob on the back of it, Do you know what the deal with that is? I've messed with it with no improvment in the needles reading, at half throttle my tach is already reading 6000, clearly not what the motor is running....
Geez, have a started a new thread?????

[DKJBama92Mariah]

Tachs have three main wires: ground, +12v, and the signal wire which goes to the ground post on the coil. It may also have separate power and ground wires for gauge lighting.

The knob is probably to switch the tach between 4,6, and 8 cylinder modes. If it is set to 4 or 6 cyl mode, it will read high.

[DKJBama92Mariah]

Do you have a picture of the offending carb? If it's a 4010, they are notorious for having hot-stall issues.

[mapleleaf]

I wanna say it's a 4160, but am not sure and no pic. This is why I dislike storing it so far away!
The adjustment screw in the back of the tach is more like a rheostatic light switcher dimmer. I"ve seen the selector for # of cyl.'s and this is a little different, just always wondered what it was for.....