PDA

View Full Version : prop slip 28%



speedfreak2030
02-05-2010, 06:02 PM
My calculated prop slip is a little high @28% ouch. 5600rpm, 1.5 gears, 86mph gps, 34p props. 30' Velocity. Gotta drop the drives lower.Had speedy 2"s TRS now. Is there a prop fix like going to a 5 or 6 blade?

Chris
02-05-2010, 06:44 PM
What's your X now that you've swapped drives?

I wouldn't get too worked up over it- after following your threads about the engine upgrades you're looking to do, those TRS won't survive a weekend. You'll either be in Konrads or doing a 3A conversion by June. ;)

ThrottleUp Props
02-05-2010, 07:01 PM
Keep in mind that when you calculate your slip on Bravo I props the stamped pitch is not true. Here is the rule of thumb on them.

From 22P-32P you must subtract one inch of pitch when calculating slip.
From 34P-36P you must subtract 1.5-2 inches of pitch. (These are all over the board when we scan them)

So your slip is really at about 24%.

So that being said you have A LOT of slip. Can you measure how far below the pad the drive is? If you take a straight edge off of the bottom of the pad directly in front of the drive and then measure how far below the centerline of the prop shaft is, please. With this info we can try to get you dialed in. I also agree with you in that you need to be running 5B or 6B props, dependant upon the outcome of that measurement.

Julie

DAREDEVIL
02-06-2010, 12:34 AM
I wonder why everybody is always concerned about SLIP #........if the speed is ok, the slip realy does not matter , a matter of fact is ..it will safe your trannys on a TRS,SSM set up !!!!!!

Check your slip # @ 35-40 MPH and then u can say WTF !!!!! LOL

But @ WOT and good speed,,,your fine. IMO

MOBILEMERCMAN
02-06-2010, 12:53 AM
I agree with Chris. Your TRS's are being pushed way beyond their limitations. Every second of effort or penny you spend on them behind 800's will be in vain. IMO. I would guess the only reason they haven't blown yet is the high slip.

Chris
02-06-2010, 09:29 AM
Can you measure how far below the pad the drive is? If you take a straight edge off of the bottom of the pad directly in front of the drive and then measure how far below the centerline of the prop shaft is, please. Julie

pic

Ratickle
02-06-2010, 09:32 AM
pic

I don't think your trim cylinders are working properly......:sifone:

inbetween
02-06-2010, 11:44 AM
I don't think your trim cylinders are working properly......:sifone:

Those are there to add transom lift :)

speedfreak2030
02-06-2010, 12:18 PM
I spray painted the drives with epoxy paint, my paint rep told me he guarantees the paint not to crack. I figure the drives are now bullitproof with that guarantee:sifone:

DAREDEVIL
02-06-2010, 12:35 PM
I spray painted the drives with epoxy paint, my paint rep told me he guarantees the paint not to crack. I figure the drives are now bullitproof with that guarantee:sifone:

HAHAHAHA,,,,,,NICE......lol:willy_nilly:

1000 HP paint !!! hehe:cheers2::sifone:

jeffswav
02-06-2010, 02:56 PM
picThat must be the magic number of "5". I just cut out my transom this morning and that is were I set mine to. The x diminsion for 5" propshaft depth is 17 1/4". Out of curiosity what props do you run?

MILD THUNDER
02-08-2010, 01:42 AM
I would think with the propshafts 5" below the bottom, and the notched transom, your slip wouldnt be so high. Either way, swinging 34p 4 blades with your power thru TRS, konrads and some 5 blades would be a route i would look into.

ThrottleUp Props
02-08-2010, 08:39 AM
My calculated prop slip is a little high @28% ouch. 5600rpm, 1.5 gears, 86mph gps, 34p props. 30' Velocity. Gotta drop the drives lower.Had speedy 2"s TRS now. Is there a prop fix like going to a 5 or 6 blade?

What is your HP... a side?

Julie

Dueclaws
02-08-2010, 11:12 AM
When you run a straight edge off of the bottom of a stepped hull, shouldn't the edge span from the transom to the nearest step?

jeffswav
02-08-2010, 11:19 AM
I would think with the propshafts 5" below the bottom, and the notched transom, your slip wouldnt be so high. Either way, swinging 34p 4 blades with your power thru TRS, konrads and some 5 blades would be a route i would look into.I think that is the picture of Chris's boat, Speedfreak has not posted any pics or given the depth of his drives yet.

speedfreak2030
02-08-2010, 01:19 PM
I mesured the distance from the bottom of the boat (6' straight edge) to the center of my gimble helmet as the drives are off and got a mesurment of 18 1/8"

speedfreak2030
02-08-2010, 01:28 PM
What is your HP... a side?

Julie

I havn't put them on a dyno but should be 725-825 hp

drpete3
02-08-2010, 01:48 PM
I wonder why everybody is always concerned about SLIP #........if the speed is ok, the slip realy does not matter , a matter of fact is ..it will safe your trannys on a TRS,SSM set up !!!!!!

Check your slip # @ 35-40 MPH and then u can say WTF !!!!! LOL

But @ WOT and good speed,,,your fine. IMOI would bet that he was hoping for better than 83 with 1600 hp. Thats what the big deal would be

ThrottleUp Props
02-08-2010, 04:31 PM
I havn't put them on a dyno but should be 725-825 hp

So I want to make sure I understand this correctly. Your going to run 725-825 HP thru TRS Drives? If this is the case.....I am going to POTENTIALLY discourage you from running 5B or 6B props. They are surely not going to help your drives life span. We may need to think a little out of the box on this one. But I may have a few ideas we can kick around. If your going to change the drive let me know.

Julie

speedfreak2030
02-08-2010, 07:26 PM
The drives are not getting changed this year. I have a L+R spare drives. Talked to Steve Stepp re: X dimension and he said 18" from bottom of the hull to drive input shaft centerline is correct.

jeffswav
02-08-2010, 07:41 PM
The drives are not getting changed this year. I have a L+R spare drives. Talked to Steve Stepp re: X dimension and he said 18" from bottom of the hull to drive input shaft centerline is correct.So where does that put your propshaft depth with the TRS shortie? A standard bravo would be at 4 1/4" at 18".

MOBILEMERCMAN
02-08-2010, 07:49 PM
After it is all said and done. The change to the shorter drives can be made to work with modern propellers. Its the ability of the TRS drive to hold up that is the limiting factor.

speedfreak2030
02-08-2010, 11:42 PM
So where does that put your propshaft depth with the TRS shortie? A standard bravo would be at 4 1/4" at 18".

I did a quickie mesurment of my TRS from driveshaft/yolk to the propshaft centerline and its 24 1/2 inches subtract that from 18" and your at 6 1/2" give or take 1/4" or so. Anyone have the exact mesurment of a TRS?

Biggus
02-09-2010, 12:25 AM
I did a quickie mesurment of my TRS from driveshaft/yolk to the propshaft centerline and its 24 1/2 inches subtract that from 18" and your at 6 1/2" give or take 1/4" or so. Anyone have the exact mesurment of a TRS?

TRS input shaft to prop shaft 24.2"

Standard length Konrad 22.53"

Konrad w/shorty lower 20.875"

DAREDEVIL
02-09-2010, 02:11 AM
Here u go............

speedfreak2030
02-09-2010, 11:21 AM
Biggus and Daredevil TRS mesurments are over 1 inch different. That seems like a lot especially when on some boats 1/4 makes a big difference. Since my drive plate is high if I went to a standard Konrad my X would be 4" and 2" for a shorty Konrad, would that be too small?

DAREDEVIL
02-09-2010, 11:45 AM
Biggus and Daredevil TRS mesurments are over 1 inch different. That seems like a lot especially when on some boats 1/4 makes a big difference. Since my drive plate is high if I went to a standard Konrad my X would be 4" and 2" for a shorty Konrad, would that be too small?

Can u post a pic of the back of your boat ???
I would still go with SSM #4...don't worry about parts, u will not break any...also they are still out there and not that hard to get ,like some people think..just not from merc !!

I don't want to get in to a pi$$ing match again with Biggus about the konrads, but for the price of 2 Konrads ( even used ) u can buy 4-5 #4's .
The gimbal change is easy aswell, since the gimbal on a SSM is bigger then the TRS, so no glass work..just drill and cut !!!!
I also have up to 3 " spacers for #4/5's avlbl. and i think u be ready to roll.
but thats just me.....:seeya:

PS, i got the mess. from the merc book so i don't know which one is off .....maybe they changed it at one point ?!
all the ones i ever messured matched the book !

PPS, then again , i think you are waisting your $$ ...everything over 90 MPH in a 30' Velocity is out of control and u can get hurt.....just ask VV on here,,he will tell u.
Nice boat, i am not slandering the make/model.....but its just not build to go that fast !

Lee
02-09-2010, 03:42 PM
A 30' Velocity is one of the first big V-bottoms to break the 100 mph mark.
I'd go with the dependable Konrads.

MOBILEMERCMAN
02-09-2010, 10:57 PM
Biggus and Daredevil TRS mesurments are over 1 inch different. That seems like a lot especially when on some boats 1/4 makes a big difference. Since my drive plate is high if I went to a standard Konrad my X would be 4" and 2" for a shorty Konrad, would that be too small?

My suggestion would be Keep your eye on the Fun Meter.

The Konrads will bolt up to what you have. Everything else requires a complete re rig. Install one of your drives and measure as Chris suggested. Find out if spacers are available for Konrads. I don't know but, expect they are available.

FYI the 18" X you mentioned is the measurement against the transom. That number is effected by the transom angle and can not be used to calculate directly as you have. The actual vertical height of a 18" X is less then 18".

MOBILEMERCMAN
02-09-2010, 11:01 PM
A 30' Velocity is one of the first big V-bottoms to break the 100 mph mark.
I'd go with the dependable Konrads.

Yes Sir. The Race boat Still Crazy went low 90's as a Modified boat with small blocks. The first one I rode in had warmed up 400's and #2's. It went 86mph in 1985.

MOBILEMERCMAN
02-09-2010, 11:39 PM
Over simplified a bit. The cut out is different and your winging the height. Aren't the tail stocks different lengths? He didn't say whether he has rear mounts.....

Biggus
02-10-2010, 08:25 AM
Swapping to a SSMIII/IV or V from a TRS is a complete re-rig. The SSM trans tailstock is about 4" shorter than the TRS. The motors will need to be moved back, X-Dimention raised. Most likely the exhaust will need to be modified also. The SSM transom cut out is also quite different than the TRS. In the end it's a LOT of work to convert to a drive package that has been long discontinued. Parts for the SSM series, even wet sump VI parts, are very getting scarce.

The Konrad system is a direct bolt-on. No modifications. Spacers are available for .5-3" in 1/2" increments.

Kurt

Biggus
02-10-2010, 08:37 AM
Here's a shot of a BW fitted with the TRS tailstock. The TRS tail is also a smaller diameter (where it slips into the gimbal) over the SSM tail. The other trans is fitted with the SSM tail, notice the differences in length.

...sorry to derail this prop slip thread, just wanted to clarify the info.

Kurt

Lee
02-10-2010, 10:35 AM
Lee, i know.....i was talking about handling ,not top speed racing.

ITS A PLEASURE BOAT !!!!!!!!

U know as well as i do that the race version is stripped to almost nothing and dialed in absolute 100% with some tricks here and there !!!!

U can't compare Apples to Oranges .:rolleyes:


Scott,
Handling is exactly what I was talking about, Fact is that old school 30' Velocity went 100mph, it does not matter what power it took to get to that speed, the hull did it.

The Konrads are plug and play.

Chris
02-10-2010, 10:58 AM
The problem with the SSM drives, beyond dwindling parts availability, is finding someone that knows how to work on them. It's an art form. And not everyone has the tools. You can get a TRS fixed anywhere.

Next you have prop selection. Small-shaft props are getting more scarce. And the difference in price- a $400 TRS prop vs a $2000 #3 prop.

As far as the Velocity goes, if you know how to drive it you can run 100 mph all day in it. But no vee of that length is all that safe at 100. They don't really get all that twitchy until over 110 or so. I had mine to 113. Too fast. I think I was out of skeg.

Biggus
02-10-2010, 11:23 AM
Sorry DD, but I've got a thing for wrong information. If one was to convert to a SSM package, the motor must be moved rearward as the SSM tailshaft is shorter. If one was to swap out the tailshafts and leave the motors in the existing TRS location, the drive input shaft would have no engagement into the trans. The SSM input shaft is several inches shorter than the TRS.

No pissing match, just factual information.

Kurt

MOBILEMERCMAN
02-10-2010, 11:43 AM
The thickness of the inner plate has nothing to do with it.

MOBILEMERCMAN
02-10-2010, 12:13 PM
I am not going to argue with you. If you did it great.

Getting it to work and doing it RIGHT are two different things to me.

speedfreak2030
02-10-2010, 12:30 PM
Great deal of info, all good. I have just come across a set of JT20 turbines 2100hp each and a set of ASD10's that I am thinking of putting in the 30' Velocity. The set up should make for a interested ride.:eek:

MILD THUNDER
02-10-2010, 02:17 PM
Great deal of info, all good. I have just come across a set of JT20 turbines 2100hp each and a set of ASD10's that I am thinking of putting in the 30' Velocity. The set up should make for a interested ride.:eek:

WTF :eek:

rchevelle71
02-10-2010, 02:22 PM
Great deal of info, all good. I have just come across a set of JT20 turbines 2100hp each and a set of ASD10's that I am thinking of putting in the 30' Velocity. The set up should make for a interested ride.:eek:

Just make sure you ask DD how to rig it:eek::sifone:

DAREDEVIL
02-10-2010, 02:45 PM
Just make sure you ask DD how to rig it:eek::sifone:

My riiging is actually pretty good and nobody ever complained ...so i don't know what this means now ????

I CAN"T BUILD ENGINES ...THATS ALL...I HATE ME FOR THAT !!!! LOL:sifone:

MOBILEMERCMAN
02-10-2010, 02:50 PM
It was a sarcastic remark. Lets not start taking cheap shots guys.

rchevelle71
02-10-2010, 03:12 PM
My riiging is actually pretty good and nobody ever complained ...so i don't know what this means now ????

I CAN"T BUILD ENGINES ...THATS ALL...I HATE ME FOR THAT !!!! LOL:sifone:


Just bustin' yer stones Buddy, yer prolly a better rigger than me, just had to do it:bump:

speedfreak2030
03-18-2010, 10:11 PM
So I want to make sure I understand this correctly. Your going to run 725-825 HP thru TRS Drives? If this is the case.....I am going to POTENTIALLY discourage you from running 5B or 6B props. They are surely not going to help your drives life span. We may need to think a little out of the box on this one. But I may have a few ideas we can kick around. If your going to change the drive let me know.

Julie

I will give you a call tomorrow. I am going to get the boat from storage and mount one of the drives to get you an actual measurement of drive depth. I have found a set of 5 blade 32p Maximus blades but will hold off buying them till we talk. Thanks for your reply, Andy...

bbladesprops
03-22-2010, 06:48 PM
I've been watching this thread too, it has some humor as well as interesting thoughts. Let me know how you progress and what you decide. I might have some test propellers for you to try. I like the thoughts of sticking to the 15/19 spline flo-torq configuration. This gives you a wide variety of stock as well as modifiable castings to work with. We carry Merc, Hydromotive, Turbo, Acme, Hering and 5 Axis as well as modify them all. 19 spline long hub cleavers are few and far between.

Brett

speedfreak2030
03-22-2010, 08:47 PM
What do you mean by 15/19 spline flo-torq configuration? I think that you are talking about Flo-torque hubs? If so that is the set up I have now with the Bravo 34p props. The props are as new never touched. The weather here has been crappy but tomorrow looks good. I will post my prop shaft depth. What other info will a prop designer/prop lab tech need?

speedfreak2030
03-23-2010, 05:41 PM
I have just mounted my drives, the distance from the bottom of the hull, folowing the hull with a 6' straight edge to the center of the prop shaft with the drive inline with the hull is exactly 5". What type of prop should I go to? I have a chance to purchase off ebay, Maximus 34p also 36p Bravo ones. Or should I tweek my 34p bravo ones? Just found out my tachs are 300rpm out instead of 5600 rpm I am at 5250 rpm @86mph

PatriYacht
03-24-2010, 04:12 PM
Years ago, when I had a Scarab with TRS, I put Hydromotive nose cones on them. The boat went the same speed, but they slowed the engine rpm's by about a hundred. I theorized that the props got a better bite in the smoother water flowing past. Also, I was only going about 60, at 90 mph, they would probably add some speed.

speedfreak2030
03-24-2010, 05:29 PM
gottem already, thanx anyways...

MILD THUNDER
03-24-2010, 09:21 PM
I have just mounted my drives, the distance from the bottom of the hull, folowing the hull with a 6' straight edge to the center of the prop shaft with the drive inline with the hull is exactly 5". What type of prop should I go to? I have a chance to purchase off ebay, Maximus 34p also 36p Bravo ones. Or should I tweek my 34p bravo ones? Just found out my tachs are 300rpm out instead of 5600 rpm I am at 5250 rpm @86mph

Where do your engines need to be WOT rpm wise is the question. I would think spinning a higher Rpm/less pitch, would be easier on those TRS. Say your engines make peak torque at 5000, and peak hp at 6000, i'd try to get as close to 6000 as you can wot, to keep from torque loading the drives. The motors would be happier too.

If 5600 is your goal, maybe the prop gods can rework your 34's. Or maybe even go to 32 bravos. I would stay away from the maximus props on your setup.