Prop removal questions...

TRBenj wrote: Sounds like you are seeing all the tell tale signs of a slow hull. On my '90, I get zero bow rise. Adding weight to the rear seat helps very little. With 4 people across the back, I am lucky to pick up 1mph. The hull is just planted, and its a lot to overcome. Check and see where the spray breaks... if its at the windshield or further forward, thats your answer!

Just went through all my pictures and videos and they are all from inside the boat. Will make sure I get some of the boat at speed next season. Tim do you think a trade off from a slow hull maybe a better slalom wake?

I agree my rpm numbers are good so the 422 is the right prop keeping it just under 5K. Would be nice to see 45mph though. Was hoping a 3 blade may help but with less pitch than the 422 that is not likely without seeing excessive rpm. Tim a three blade 12.5" prop with 15.5"-16" pitch would be a nice option if available. Looks like I have a excuse now for wimping out on the barefoot experience.

Steve and Mike get some numbers and pictures of the boat at say 30mph 35mph and 40mph to match your prop testing numbers. This would provide some real nice reference material for all us Sport owners. Hey now that Keith has one you will be helping him out as well.

TRBenj wrote: The big discrepancy between the speed and RPM would suggest that you have a slow hull. Where does the spray break when youre at skiing speeds (30+)? My '90 also has a slow hull... runs very nose planted:

Tim, now looking at your photo compared to the only photo I could find of my SPORT running at or around 30 mph and WOW what a difference. It almost appears your spray breaks in front of the windshield, while I can't see exactly where (in relation to the windshield) it breaks on the SPORT, it is definitely aft of where it breaks on the 90 SKI. Also, there is probably some variation due to water conditions, but still the difference seem pretty big.

lewy2001 wrote: Tim maybe it is a slow hull. My thoughts were the 1442 being a 3 blade may have a higher top speed. If it has the same rpms as the 470 though it will not be that usable (5200rpm). Tim do the 470 and 1442 tend to run the same rpms versus speed? What do you think of the OJ 428?

The 3-blade vs. 4-blade argument is secondary to propping your WOT rpm's to your power curve. The 3-blade will have an advantage, all things being equal... but if it puts you 200rpm further from your hp peak, then things are NOT equal. I wish Acme would make a few 3-blades larger than the 470 and 1442 for the 1.23's, as the higher powered boats (HO 351w's, 6.0L's, etc) could benefit from one. Boats like the Crush and Joe's stroker only have 4-blades to choose from. I doubt youre going to do better than the 422, based on the RPM's youre seeing with it.

Ive never tried the 428, but Id like to. Ive tried the 430 (428 with extra cup) and I really disliked it on both my '90 and the Crush. I believe the 428 should turn very similar RPM's as the 668 Acme (which is a 422 with extra cup), or maybe a touch less. Even the Crush couldnt turn the 430 (~5200rpm, vs. 5550-5600 with the 668). I doubt the 428 would be the hot speed prop though, as OJ's tend to make the boat run a little more bow-down. Might be a good choice for slalom.

lewy2001 wrote: The speed numbers with 400lb ballast did not change very much(less 0.5mph). The attitude of the boat did not change much either, it still ran very flat. Almost zero bow rise when you go WOT. This was one thing I really noticed going from the 89 2001 to the 98 Sport almost no bow rise on take off. Have never paid much attention to where the water breaks on the hull but I will next time. Maybe I should have added 2X 400lb bags and see if that gets anymore of the hull out of the water.

Sounds like youre seeing all the tell tale signs of a slow hull. On my '90, I get zero bow rise. Adding weight to the rear seat helps very little. With 4 people across the back, I am lucky to pick up 1mph. The hull is just planted, and its a lot to overcome. Check and see where the spray breaks... if its at the windshield or further forward, thats your answer!

mdvalant wrote: I'll work on getting some numbers. I never have time for fiddle faddle I just kinda wing it and go by what feels good to me. Had the 422 on the sport yesterday after a full recondition from ACME and I didn't really like it all that much........ 654 still my favorite though by far. If my memory serves well none of our props were under the 44mph mark on GPS. They were all 44-45 with one driver and rider full tank of fuel.

Mike what rpms were you seeing with the 422 at WOT??
My 422 is just back from the prop shop also so I wanted to get the numbers before I get a chance to hit some more debris. It is a better prop than the OJ 13 X 16 smoother and does reduce rpms at skiing and boarding speeds. The OJ is quite a good prop for this hull and does produce a slightly better top speed. It also handles small hits from debris better than the ACME. Both props have plenty of pull, the ACME is slightly better. We never use it to pull more than 3 people so never have the need for less pitch like your application. How many rpms are you seeing at 36mph with the 654?

Tim maybe it is a slow hull. My thoughts were the 1442 being a 3 blade may have a higher top speed. If it has the same rpms as the 470 though it will not be that usable (5200rpm). Tim do the 470 and 1442 tend to run the same rpms versus speed? What do you think of the OJ 428?

The speed numbers with 400lb ballast did not change very much(less 0.5mph). The attitude of the boat did not change much either, it still ran very flat. Almost zero bow rise when you go WOT. This was one thing I really noticed going from the 89 2001 to the 98 Sport almost no bow rise on take off.

Have never paid much attention to where the water breaks on the hull but I will next time. Maybe I should have added 2X 400lb bags and see if that gets anymore of the hull out of the water.

No no , sorry Pete I shoulda used the quote feature

Ed had asked way back up the thread about his new acme having machining marks(grinding)

the grinding on the new acme is normal---balancing the prop

Yes, you'd have room to run that 1442 (I believe Mike has tried it on his Sport as well). I probably wouldnt though, as it will turn ~200 more RPM than the 422, so very similar to the 470. Youre propped just right if your turning just under 5k.

The big discrepancy between the speed and RPM would suggest that you have a slow hull. Where does the spray break when youre at skiing speeds (30+)? My '90 also has a slow hull... runs very nose planted:



Short of taking a grinder to the hull and removing some hook, theres not a lot you can do about that.

lewy2001 wrote: Posted: 23-May-2011 One of my winter projects is to back to back both props with full data.

Better late than never that was almost 12 months ago. Yesterday was such a pleasant late Autumn day. Far to good to be in the office doing paperwork for the Tax department.



Conditions 26C(79F) No wind.
98 Sport GT40 full tank of fuel driver 88kg(195lbs) and 30kg(66lbs)dog in bow walk through.

GPS PP Stargazer readings.

ACME 422 12.5 X 15.5                  OJ 13 X 16 Legend (Original)

2000rpm    14.5 mph                    2000rpm    14.1 mph
3000rpm    29.1 mph                    3000rpm    28.0 mph
4000rpm    37.5 mph                    4000rpm    36.5 mph
4500rpm    40.3 mph                    4500rpm    39.8 mph
4940rpm    42.0 mph                    4970rpm    42.7 mph

Added 400lb Fatsac in rear locker and rerun WOT tests

4960rpm    42.3 mph                    4990rpm    43.1 mph

The top speed is disappointing especially when others have top speeds over 45mph with less rpms on same hull. The engine feels strong but does have a few hours on it. The rpms achieved indicate that it is pulling well just not getting good speed numbers. I have seen 5200rpm on this engine previously but that was with a Acme 470 which only lasted one day on the boat as the rpms were 200-300 higher right through the range.

The original tach in boat is quite accurate but the Stargazer one gives you 10rpm increments hard to read the analog that fine. The water was glass and this may have slowed boat. No chop or ripple to get some air under the hull.

The reference section had some numbers for the Sport and SN for 95 and 96. Not sure if these numbers would have been GPS certified but 46.6mph for the Ski and 47.5mph for the Sport. I remember the first time I found those number I was surprised that the larger Sport hull was faster.

In 98 the factory did some small changes to rear chine cutout plus reduced the shaft angle. I wonder if that slowed the boat down over the previous Sport 93-97?

Mike or Steve did you ever get full GPS readings on your hull with either the Acme 1442 or 422.

Especially interested in the numbers for the 1442 Mike.

Pete or Tim do you think I would have enough hull clearance with the 1442 prop. The 12.5" 422 has 1.375". The 13.25" 1442 would have only 1" by my calcs.

Well I think I'm going to try the 654. I'll let you know how it goes.

I think the new boat will suit our needs great. The Sport w/ the PCM transmission sounds like crap compared the BBC with the velvet, so the 85' is definitely more fun to cruise around in.... We may keep both, I like the looking out at the detached and seeing this.

mdvalant wrote: Feels great! I want to test out our 654 but will be reluctant to take this one off...

Mike,

Did you ever test the 654? We ended up getting the 99 Sport and it has the stock OJ on it, but also came with an Acme weekend saver kit with a 654 in the bag .

From our test ride I felt like the stock OJ was slipping a lot out of the hole, I'm thinking the Acme would be better.

Hey now Pete, how do you know those flats weren't already there from a previous removal? Give the guy a break.

gun-driver wrote: Looking at the two flat spots on the hub in the same picture, I think Alan guessed it right.

Ha I missed that but by the size of that wedge I think it was a universal prop removal tool AKA a BFH.

81nautique wrote: DId you happen to use a wood handled hammer while removing the prop because that looks like a handle wedge. Check your hammer maybe it fell out.

Alan,
Thanks - now I see it!! I think you're correct.

gun-driver wrote: I'm not sure if it's the angle of the first photo, but it looks like your due for a new cut-less bushing. And it looks like the shaft isn't aligned to well, it looks like its riding against the 7-8 o’clock part of the bushing. What do ya think Pete??

Paul,
I agree.

Ed,
You had better check it. Also, the shot of the "wedge" isn't the greatest. How about another picture? You've got me real curious!!

I'm not sure if it's the angle of the first photo, but it looks like your due for a new cut-less bushing.
And it looks like the shaft isn't aligned to well, it looks like its riding against the 7-8 o’clock part of the bushing.

What do ya think Pete??