Prop slip questions

[HOWARD O]

How much slip is acceptable with a TRS? The 22 has a 24" pitch Turbo1 and it seems to bite very well, gets decent lift but it doesn't seem to do much between 4k and 4600 RPM. If I let it cruise for a while at 4000 RPM, it'll eventually get up to 54 mph. However, it starts to get a lot of slip between there and the 4600 maximum RPM. It'll eventually reach 60 mph at 4600 RPM, although I shudder to leave the old motor there for too long. Seems to be propped well, will go only a nose past it's max of 4600.

So, according to a prop calculator, I am getting a little over 9% slip at 4k RPM, which seems reasonable, I guess. At 4600, I am getting 14% slip. Also, it doesn't "feel" like the prop is doing much past 4k rpm. I can hammer it to 4600 and it goes there almost immediately, w/out any feeling of further accelleration. Hope I conveyed that right? If I could keep the same 9% slip at 4600, I'd be seeing around 63-64 mph. Next I'll check the speeds at all RPM's.....see what it's doing as far as slip.

So is the prop losing some bite at higher rpm's? I am not feeling any transmission slip, even when getting on plane, so I don't think that's the culprit. I am interested to know if one of those 4 blades may help some? How would a 4-blade compare to a 3 blade, would it provide even more aft lift?

Probably bad timing for these questions, Grizz might be "involved" in something a little more interesting! :D

[VetteLT193]

sounds like a lot of prop for the power. good for cruising though... depends on what you are looking for overall.

I'd guess you have about 2 - 3" too much prop... I'm also guessing you are using a lot of trim to get to 4600 RPM.

[HOWARD O]

It's almost the opposite, it has no problem at all getting to 4600. If I nail it at 4000 rpm, it'll get to 4600 almost as fast I can push it down. But the prop never seems to fully "catch up". Does that make sense? :confused:

[VetteLT193]

It's almost the opposite, it has no problem at all getting to 4600. If I nail it at 4000 rpm, it'll get to 4600 almost as fast I can push it down. But the prop never seems to fully "catch up". Does that make sense? :confused:

Makes sense, good clarification. What's the ratio? have you played with the trim much?

[HOWARD O]

Makes sense, good clarification. What's the ratio? have you played with the trim much?

It's 1.5 ratio. I've played with the trim some, but I don't think I've trimmed up all the way. Still haven't figured out what's wrong with the gauge and I really can't tell if and when I have hit the limit. It does feel like I have a good deal of the boat outta the water. Still new to me though, and I admit I need more seat time to figure out what everything is doing.

[Lenny]

Your slip numbers should be going DOWN with increased RPM's. Not up.

Something is amiss.

[fogducker III]

Spun prop hub...?

[Planetwarmer]

Sounds like cavitation. Make sure that your zink cav plate above your prop is still intact. Does your prop have nicks in the leading edge?

Your gauge may not work properly if the little thingy on the drive gets water in it. See if it works dry. If it works when the boat hasn't been put in the water, but quits after you get the boat wet the sending unit may have a leaky seal.

Try to not trim the drive as high, and see if that helps. Over trimming a boat is very common. Try "under trimming" and see if that makes a difference after you check the other things.:smileybo:

[Ghost]

Spun prop hub...?

Had the same thought. I have not experienced this in my adult lifetime, so I don't know to what extent it can hold up under lesser load, and slip under more load. Just seemed like something that *could, in theory* fit the symptoms. Real life, dunno.

[HOWARD O]

it's most likely the wiring going to the trim position sensor....I rigged it and it worked for a short time, but it's that old lamp cord looking stuff. I'll just replace all of it.

I don't know, I have a pretty good feel for where the trim is at a given time.....definitely not over trimming. Propeller itself is in perfect condition, not a nick or scrape on it. Don't know about the hub, I shall inspect that this week. This wind isn't helping today!

Thanks for the feedback. Spun hub has it's possibilities.

[mattyboy]

a spun hub is not going to get 60 mph it will be evident when trying to get onplane ??? does the boat have a rev limiter?? a drop of 2- 3 inches of pitch is going to put him over 5k sounds like he doesn't want to spin her that fast ????

something is a miss though cavitation or ventilation

[Lenny]

Had the same thought. I have not experienced this in my adult lifetime, so I don't know to what extent it can hold up under lesser load, and slip under more load. Just seemed like something that *could, in theory* fit the symptoms. Real life, dunno.


Spun one last summer on the X. Good for about 10 mph only tho. Definately NOT 4000 rpms.

[Ghost]

Spun one last summer on the X. Good for about 10 mph only tho. Definately NOT 4000 rpms.

Gotcha--I know the one when I was a little kid was breaking loose below planing speed. Never knew enough to know if it might have shown some slighter symptoms earlier, at high RPM. Sounds like no.

[fogducker III]

Not sure what set-up you have Howard? is it the rubber "dampner"? If it is, then it might just be your problem, depending on conditions they let go at weird times, I agree Matty, usually when getting up on a plan, but not always.......

Once on a plane though and then giving it some power will show the symptoms described......an easy way to check is to scratch a tell-tale mark on the hub lip and the edge of the prop, go run it and if the two marks are not still lined up when you get back, re-hub the prop.

[mattyboy]

again I have never seen a spun hub that can eventually climb to 60 mph at those speeds once spun the condition would only get worse
Howard if the numbers are right I have you at 10% at 4000 and 13% at 4600

not sure what you have engine wise

the tach needs to be verified

my 16 would ring out a few mph after being held at wot for a bit take a moment for the prop to seem to get into a groove

I would tend to agree with the trim and ventilation statement even in my mind if it were cavitation that would be a total lack of bite it would break loose and jump past 4600 or bump the rev lim. and speed would decline

[mjw930]

There's nothing wrong with the hub or you would never get the boat on plane.

Have you verified the speeds with a GPS? The speedo may climb slowly but that may be a function of the gauge, tubing or pickup and not be reflective of your actual speed.

On my boat when I hammer it from cruise it jumps to 4500 then, once the slip settles and the boat gets up on top of the water it moves to 4600 - 4700 and the speed goes from 60mph to 65 mph on the speedo (63 on GPS). Mind you I'm turning a 23P with a 1.5:1 ratio B1. It's interesting that you have a 24P prop on a TRS and see more slip. Perhaps it's a function of the TRS vs. the B1, I don't know.

[Air 22]

IMO...Boats/Props are kinda like snowflakes(sorry FL guys/gals).:)..they may look the same from a distance but up close no 2 are alike...and thus the prop #s and driving skills produce different results...ya just gotta test and test again til yazzz R happy....:smileybo:

[BigGrizzly]

I am in from the shop. Howard you have a 330 TRS. The slip sounds high I doubt the hub is soun with that prop when the hub spins you know it, no question. What is happening is your tabs ate draging and it is lifting the boat so it looks high but it is really wet. A couple of things. Check the tabs if you have a question e mail me a picture and I can tell for sure. The next the prop should be a 23 and spin it to 48-5000. Don't wory what the book says it doesn't matter. Your trans is not slipping either when it does revs will hit the ceiling. The trans either slips or it doesn't it. it has an internal clutch that is locked or not locked only two positions. Another thing that may help with the TRS is a little bit bigger diameter as a TXP. That boat should be doing 62 or 63 mph at wfo.

[HOWARD O]

I don't know, maybe mjw930 really has nailed it. I have always had a fear of leaving the motor, any motor, wide open for longer than 30 seconds or so. :embarasse Maybe I'm just not leaving it there for long enough. All my speeds are GPS.

Grizz, I'm pretty sure we can cancel out the trim tab idea, I have none! :D More I think about the spun hub, that of course wouldn't make sense if it's not acting up on take off. I'm pretty easy on it during take off, but I've put the coals to it once or twice. Well, as many coals as this 330 will generate anyway. No problems.

I'm probably over-thinking this as usual and not giving it enough time. I don't even really care if it's 60 or 64 mph....it's just that I would want to know if something weren't right.

Thanks for all the ideas. Grizz, I am pleased to know about the tranny being either on or off, that was a good way to explain it to me. I wasn't really sure if it could be slipping just a hair, but now I know it's not.

[BigGrizzly]

I forgot to tell you, The TRS likes a lot of trim. The trim pump is slow and the indicator stinks. The is the fly by the seat of your pants thing. You really need to stay in it longer. That is a strong motor, at least for durability. I beat mine really hard when I knew I was building the 502, and it just came back for more. That is why I kept the engine.

[HOWARD O]

I'd probably be less gun shy about running the motor hard if it were the END of the summer! :D

My gauge isn't functioning and I always forget how slow the trim is, I'll have to give it some more. I at least know the limit function is working though. Thanks Grizz....

[mjw930]

I'd probably be less gun shy about running the motor hard if it were the END of the summer! :D
My gauge isn't functioning and I always forget how slow the trim is, I'll have to give it some more. I at least know the limit function is working though. Thanks Grizz....

While still in cruise mode run the trim up until you feel it start to slip (slight bump in RPM or drop in speed). Then lower it slowly until it "hooks up". Use that setting as a baseline for your speed run. Throttle it up and see where it tops out then bump it up until you feel it slip (hopefully you have a rev limiter, you should if you have the Thunder Bolt ignition). You can bounce the motor off the limiter for short durations without worrying about it. The internals can take sort runs to 5600 RPM before the valves start to float so 5200 or so on the limiter shouldn't be any problem.

[VetteLT193]

I agree, has to be trim but opposite of what I originally thought. I thought you weren't trimming enough but I think you have it trimmed too much.

I have a feeling that if you trim it normally you may not get the RPM out of the 24 pitch. that might be why you have the trim so high to begin with.

It's nothing but a gut feeling without being in the boat. 24" seems like a lot of prop when the factory was putting 21" cleavers on with the same amount of power... but that is apples to oranges with drives too.

[handfulz28]

Correct me if I'm wrong Howard, but don't you have Cuda's 22 now? Aren't there a couple of parts that aren't stock on that motor? ;)

[HOWARD O]

Whoa Phil, are you telling me that all thunderbolt ignitions have built-in rev limiters? This is news to me....big news if true. If so, at what RPM???

[HOWARD O]

Correct me if I'm wrong Howard, but don't you have Cuda's 22 now? Aren't there a couple of parts that aren't stock on that motor? ;)

I do have his 22. Internals of motor are stock. Other than that, it has an aftermarket intake, thunderbolt ignition and Dana exhaust. That's about it.

[mjw930]

Whoa Phil, are you telling me that all thunderbolt ignitions have built-in rev limiters? This is news to me....big news if true. If so, at what RPM???

TB-V's have limiters, 4750 for 7.4L and 5250 for 454 Mag's (I think). I thought TB-IV's had limiters too but I'm not sure which modules and what the limits are.

[HOWARD O]

Hmmm.....it does have a IV in it now and the module is a V8-24. I do have the timing chart for this specific module but no mention of a limiter. That doesn't mean it doesn't exist I guess. The TB-V chart isn't specific, it just a general range of where the advances come in. Furthermore, I have no idea what application the Tbolt V ignition that I have is made for anyway.

Gosh, now that the engine is running decent, I am tempted to put the tbolt V back in just for grins. Several people here seem to believe that it'd never be right without the knock module hooked up.....but that didn't seem to be a problem before.

Only reason I am curious about this is that I was running it to around 4600 today and it was acting funny, as if it was getting a repetitive fuel restriction in small increments. Rev limiter never occured to me but that is exactly what it felt like.

I have a Clymer manual that covers both TB-IV and V but they don't have any advance charts in there nor do they say anything about limiters. I think I'll need to find this out!

[HOWARD O]

Okay, scratch that. I've learned the TBIV does NOT have a limiter..... :smile: