moving props.

[waimo]

ok i under stand moving the prop towards the strut lifts the nose up and taking it away from the strut lifts the rear up.with out replacing the prop shaft each time our machineing the prop shaft taper how is it done ?.

[RiverRacer]

Depends on how much it needs to be moved, the prop needs to be as close to the strut as possible, you can move it slightly back with a couple of nickles between the propshaft and the v-drive output shaft, or vice versa if you have the room, or if the prop needs to go back an inch or better then you can cut the plates shorter, or the other way around you can make longer plates, other than that it's move the strut, and if the strut is not in the right location to begin with, it needs to be moved!...

[waimo]

Thanks Art but what are nickles.do you ever sleep?.

[SonnyGlide]

Racer: I know were yack'n on this off site, but how close should the prop B to the tube, I still need to get my puller behind the prop to pop it off'a the shaft
Just close enough to get the puller on close enough?

JJ make new struts and longer shafts per my situation on the Sanger?

[AquaCraft]

Waimo,

A Nickel is a Yankee coin, it's about as thick as one of your Schillings...

Aqua-Craft

[RiverRacer]

Thanks Art but what are nickles.do you ever sleep?.

Nickles are coins, just under an inch diameter and make good spacers!.. Sleep, yeah when you're awake!..:D

[RiverRacer]

Racer: I know were yack'n on this off site, but how close should the prop B to the tube, I still need to get my puller behind the prop to pop it off'a the shaft
Just close enough to get the puller on close enough?

JJ make new struts and longer shafts per my situation on the Sanger?

Close enough just to get the puller on, in fact some grind the puller down to get it even closer!.... You have an 8 degree strut right, no need to change it!..

[boatracer]

Thanks Art but what are nickles.do you ever sleep?.


about $2 in our money waimo:D:D:D

[RiverRacer]

about $2 in our money waimo:D:D:D

Not any more it ain't!..:D

[waimo]

prop needs to be moved up further so i will get the shaft redone and see what happens.only concern is that its a log which rock and roll like a skiff so it may not be that easy to notice any change.

[RiverRacer]

Depending on how much you move it, it will be noticeable. Just remember it's nothing whack the shaft off but it's a bitch to add it on, so it's best to do it in small increments!..

[waimo]

Thanks Art was thinking about getting the taper done for a start as the new prop wont go up as far as the old one.

[RiverRacer]

Thanks Art was thinking about getting the taper done for a start as the new prop wont go up as far as the old one.

Are you sure it's the taper that's wrong????, did you try the prop without the key first?????..

[Moneypit]

Cut it off on the v drive end and you won't have to mess with the taper. Like Art said, small increments, 1/4 inch is a lot.........MP

[waimo]

yea its the taper.tried lapping it in with valve grinding paste and found the back of the taper wasent a good match.so it had to be done.just needed to know how far and how to move it back.the season is about over so its time for the big jobs and a new motor.thanks to Art now run a vertex and going to try crower injection but stay with gas.

[RiverRacer]

Weird, those are a standard better check the prop, are you sure it didn't go all the way on or is the hub on the prop thicker??, might want to recheck that put the old one on and mark the shaft on the front, then put the new one on and see if it goes up all the way to the mark!..

[tunnelrunner]

What breed of prop is it waimo? Reason I ask is that there are at least 2 weird-ass proprietary tapers apart from the std. Morse floating around over here in Oz. Maybe a prop (or a shaft) made its way across the Tasman?

[waimo]

new prop is a menkens.the old prop is a menkens but had been around the block a few times look.had to change props after turning motor around it is now driven off the flywheel.

[tunnelrunner]

no worries, that discounts that theory then !:)

[E-boat racer]

I believe that the standard prop taper is 2 degrees per side for a total shaft
taper of 4 degrees. When you set it up in a lathe, the angle (taper) is
set at 2 degrees. Don't mess up a good shaft trying to match a goofy
prop bore.
Rob

[mike c]

Art,
How would cutting the plates down be the same as moving the prop back with a nickles in the coupler, aside from the physical dimension of the prop from the end of the cavitation plates? If moving the prop back as waimo said lifts the stern, doesn't cutting the plates down cause the bow to lift and vice versa? Not trying to argue just trying to understand for my own benefit. thank you.

[RiverRacer]

Mike, The plates are an extension of the bottom of the boat, so changing plate lengths is just like moving the strut, so if you were to cut say an inch off the plates it would be like moving the strut back an inch, and moving the prop back does not give you bow lift, it's the opposite!..:D

[mike c]

thank you for the reply,
Can you help me with the set up I have because I was wondering about plate and how it affects porpoising. I read the thread about "dry" and his boat setup, I have roughly the same set up as he does with a few minor differences. I have a 73 sanger circle runner with a 468BBC normally aspirated, solid lifter cam, oval port merlin head(iron), performer intake, 850 holley and dry stacks. I'm guessing btwn 500 and 600 horse. The motor is 39 inches from the transom to the front of the motor(driven off the flywheel), 12% overdrive, 10 degree casale, strut is 9* , V-drive is at 86 inches to center plate, the prop is an 11 1/4 X15 that was cut to 11 1/8 and is just barely a 15 now. The work was done by a reputable shop here in the bay area, but it was not enough to get rid of the porpoising. Based on the thread I spoke of earlier I thought this would help. It did not lift the stern at all. Burns like hell coming outta the hole to 5,000rpm then hooks up but I can't get off the down pedal at all not even a little. I moved the motor forward from 35 inches to try and help this as well. This helped it to turn alot better, but still porpoised. This past weekend I fabbed up some 2 inch aluminum plates to ad to the cav plates it seemed to drive the bow down but I still can't get off the down pedal not even a little. The bottom appears to be straight and the cavitation plates are 9 inches off the transom, level with the bottom and an 1/8inch down on the starboard side. When I ran it last weekend it appeared that the ass was dragging so I'm guessing I need more transom lift? Any help is greatly appreciated I don't have a problem buying a new prop I just don't have the money to spend on a bunch of them. I'm only at weekend warrior status. Thanx again for any help.

[mike c]

I guess I should probably clarify my intentions. I'm trying to set the boat up to run in the nostalgia flat class in southern california. The class mandates a 80mph speed limit with 12's at 6000rpm will put me in the ball park. So I'm trying to get the boat to set at lower speeds. Is this possible? It seems like these boats need a ton of horsepower and a ton of speed to run properly.

[Moneypit]

Sounds like a plate rod, to turnbuckle shaft, to plate, problem....Check the actuating arm for slop on the shaft. The keyways wear out and allow the plate to move up even though the setting is down while at rest. Have someone watch the movement at the back of the boat. There should be NO slop in any of the plate linkage. Have a couple of buddies hold the plate UP while you try to push it down with the pedal and watch for play. ..........Just a shot..........MP

[mike c]

Thanx Moneypit,
The acuating rod is welded to the transom shaft as are the levers. The levers are at approximately 1:30/ 2:00 position as viewed from the port side of the boat. I also checked the travel of the plates this weekend and came up with 3/4 to 1 inch of travel. The reason the dimension is so vague is because I checked it with it in the water, my wife pushing on the down pedal and measuring to the surface of the water. The boat sits on the trailer with the cavitation plates on the bunks. All the other linkage appears to be tight, there is a little bit of play in all of it but it seems to be negligble. Would moving the prop back possibly help, the reason I am worried about doing this is because the prop is already 3/4 of an inch away from the rear of the strut barrel. The shop that did the prop work said they could add length to the barrel if that worked but I'm worried about just trying it any further back. Do you think if I just ran once or twice to test that it would be okay?

[dry]

Mike c,
The 1st time i thought my cav plate was level and i ran it it porpoised like a big dog when i barely tried to get off the pedal. A v drive friend of mine measured my plates and told me to reset the plate because what i was calling level was close to 3/8" up. Mine has the gull style bottom and was kind of hard to put a square on, when i checked and adjusted and rechecked and adjusted and rechecked to what i felt was level with the square i then could hammer it and burn about 5k in the hole full down and start coming off the pedal at about 3-4 seconds into the run about 3/4 from full pedal and pull anywhere from 7200-7500 if i came off the pedal anymore than about 3/4 it would try to hop and this was untill my steering cables loosened again and made it hard to drive. this was 2 weeks ago last time out. I think i am getting close to the right set up finally not there yet but seems to be getting closer. I don't know if this helps but i thought i would let you know where i am at.

[mike c]

I appreciate your update Dry, I was wondering how it was going since i was following the other thread and hadn't heard anything recently. So do you have 1" of space btwn the front of the prop hub and the strut barrel or is it closer than that? I will recheck my plates to make sure they are level with the bottom again. I checked them with a 4' level but maybe I was not holding the level tight enough to the bottom I don't know it's been awhile since I checked them. What gears are you running? 7200-7500rpms seems like alot!:eek:is that when your 3/4 off the down pedal? thanx again.

[RiverRacer]

Mike, 7500 is not a lot gotta unload the motor so it can pull the boat, if all you can pull is 5500-6000 then you're lugging it and it don't have the power to hold the boat on a set, so you have to gear and prop it for the power you have!.....

Now, I just re read all this stuff and first of all do not move the prop back any further, it's already too far back from the strut it should be just back enough to get the puller on it!.. From what you're saying you're blowing the prop away on take off, so send the prop to someone that knows WTF they are doing, it needs a cup and maybe more?? that will also help lift the tail, send it to Tom and get it fixed 530-885-0531!...

Another big factor, you say the plates are 9" long that is too long, what is the distance from the back of the tube to the back of the transom????..

[dry]

I appreciate your update Dry, I was wondering how it was going since i was following the other thread and hadn't heard anything recently. So do you have 1" of space btwn the front of the prop hub and the strut barrel or is it closer than that? I will recheck my plates to make sure they are level with the bottom again. I checked them with a 4' level but maybe I was not holding the level tight enough to the bottom I don't know it's been awhile since I checked them. What gears are you running? 7200-7500rpms seems like alot!:eek:is that when your 3/4 off the down pedal? thanx again.

Yes that is at around 3/4 or so off the down pedal at 7200-7500 with 12's and a stellings 11 1/4 x 15. I will have to check my prop space and my plate length and let you know. I still haven't got mine to set yet, i still have to lightly pump the pedal to keep it planted, but being off the down pedal about 3/4 seems to keep it pretty stable, i may have to adjust the plate with alittle more down.......? I am still learning as well.

[RiverRacer]

i still have to lightly pump the pedal

Pumping the pedal is not good, hold it at where the boat don't hop, but you should be off the plate at speed!..

[Terrible toy]

Pumping the pedal is not good, hold it at where the boat don't hop, but you should be off the plate at speed!..

Absolutely correct advice. Only reason to be on the plate when the boat is set is if something causes the nose to come up on you.

[dry]

I guess i explained it wrong its not an actual pump i let off the down to about 3/4 off and hold it there, but then again i keep trying to let off a little more which keeps me going back to 3/4 or so off.

[mike c]

Thanx for all the response,
Art, the distance from the back of the tube to the transom is 16 1/4 inches measured along the bottom of the boat, not at the pitch of the shaft. If you need it at the pitch of the shaft i can get that also. I've always been told 6500 rpm's was the safe limit for 3/8 rod bolts with stock rods on a bracket drag motor in a car, due to average piston speed. So my thinking is this is a marine motor that has to pull some rpm's for quite awhile, what is a heat race like 5 laps, I think? The motor pulls hard all the way to 6500rpms, so should I change out the rods to 7/16 ones or can i get away with changing my gears and prop combination. I would rather spend the money on a good stainless prop than on a set of rods. plus i'm to much of a chicken shit to go past 85 mph anyway.;)

[RiverRacer]

Thanx for all the response,
Art, the distance from the back of the tube to the transom is 16 1/4 inches measured along the bottom of the boat, not at the pitch of the shaft. If you need it at the pitch of the shaft i can get that also. I've always been told 6500 rpm's was the safe limit for 3/8 rod bolts with stock rods on a bracket drag motor in a car, due to average piston speed. So my thinking is this is a marine motor that has to pull some rpm's for quite awhile, what is a heat race like 5 laps, I think? The motor pulls hard all the way to 6500rpms, so should I change out the rods to 7/16 ones or can i get away with changing my gears and prop combination. I would rather spend the money on a good stainless prop than on a set of rods. plus i'm to much of a chicken shit to go past 85 mph anyway.;)

That's what I thought you're plates are too long, 7 1/2" would make a world of difference, especially after you get the prop fixed!... I ran 3/8 bolt rods for years, a detailed rod with good ARP bolts will run 7500 no problem, but with the aftermarket availability today it don't make sense to bother with factory rods, the aftermarkets are way cheaper and way stronger!...

[mike c]

Ok, with all this said, what I should do is cut the plates down to 7 1/2 inches in length, use my same prop 11 1/8 X14-15 have some cup put in it, move the prop closer to the strut(just enough to get a puller on), change my gears and spin the motor up higher? If I change the gears out should I increase the overdrive to say 15% or decrease to say 9%? If I'm trying to increase lift by spinning the prop faster I should increase the overdrive correct?

[RiverRacer]

Well, I would never do more than one change at a time, but in you're case I'd make an exception with a brand new start!.. If it was my boat I would move the prop close to the strut and cut the plates right off the bat. Now the prop, I don't understand what you mean by 14-15, but I would not change gears I would cut the prop down or better yet borrow a 10 7/8 or 10 3/4x16 and try it then go from there!..

[mike c]

Thanx again for all your help,
The 14-15 was told to me by the shop that cut the prop down to 10 1/8 from 10 1/4. They said taking the radius out of it reduces the pitch slightly. I'm not sure if this is true or not. I think I will call Tom Bentley. I'll do these changes and let you know how it goes. May take a little while to get done been pretty busy with work. Thanx again.

Mike

[RiverRacer]

I think I will call Tom Bentley.

And then send it to him!..:D