Tested props turning out and shutting down throttles.
 

I realize with TooOlds daughter posting pictures all over the board, nobody cares. But I thought I would follow up the discussion from a previous thread, "HTM Mishap."

I had Eliminator switch the props so they are turning out (thanks Ron P for turning me on to T2x's thread - awesome!). Bob Leach looked pretty disappointed when I told him, said I would loose 5 mph off the top end. Best I could tell, I lost 4 mph (same weight, gas, temperature). But boy oh boy did I make up for it in handling. With the props turning in, I could barely get the thing to turn above 65 mph. With them turning out, I was carving U-turns up to 70 mph and course corrections at top speed (77 mph, still had the 26" props which limit me to 4,400 rpm). The really cool part was anything over 50 mph the boat was leaning in on the turns! I really liked that. The leaning out thing with the props turning in was spooky!

Considering how few boats where on the lake and how calm it was, I went ahead and tested shutting down an engine at different speeds. I couldn't have been more pleased with the results. All the way up to 70 mph, either side, the reaction to quickly shutting the throttle down was mild. In fact, on the last day, I shut them down while my hand was off the wheel. The boat started to turn to the dead side, but it was mild. I did the no touch trial up to 60 mph (at which point I ran out of balls - not the boats fault).

Boats back at Eliminator so they can finish the tunnel modifications. Hopefully, I'll have the 27" props next time. Plan on continuing the test to higher speeds as long as the reaction stays mild. Not really excited about being a test pilot, but I think its important to know. If any of you have experience with this, I would love to hear it!

Uncle Toys, I am really glad to hear your results with switching the props around.

I wonder if Eliminator chose to spin them in or if they don't think it makes a difference so however the drives go on is OK by them.

It sounds like you can now relate to how poorly a cat can handle if the props are spinning in. Could this be what happened to the HTM?

How did the boys at Eliminator react when you explain the rotation theory to them?

Leaning into a turn in a cat really kicks ass! I'll give up a few mph too if I could make it so the boat didn't scare that **** out of me every time I turned the wheel.

Take a look at the photo under my name. This is what happened the one and only time to ran a race with the props spinning in.

Two bad it was the second race in the Worlds in Key West.

Ron P - I'm with you on giving up the speed for the leaning in. That was totally "kick ass." It will be interesting to see how it handles in choppy water. All I can find this time of year is glass. Haven't had a chance to tell the Eliminator guys yet. We are going to stop by there tomorrow on our way out to see Cattitude's jeep competition. If I get a chance I will discuss it with them, but damn they are busy right now. Considering this is their first twin 26' Daytona, they couldn't know one way or the other. They probably just went on experience from the 28' Daytona.

Unc,
Glad to hear your results were positive, I have also found that the handling on both of our cats was best spinning out. Spinning in didn’t show any better speed on both the 28’ and 32” Skater. We did the swap “In vs. out” on the same day, a few hours apart. The both boats turn like they are on rails, the lean is to the inside of the turn not the outside, and If you get out of shape, one sponson going up, the other one going down, jumping on the power will force the high side down. I think you might find the 4 MPH difference might not really be there. Run the boat, trim for top speed, record the GPS MPH, come in and swap the props and go back out, and check your speed. I think you will find the boat will run better in the rough also, Spinning "out" tends to hold the stern down, and allows the bows to pivot up and over the waves easier.
Philip

Thanks Philip! Funny you mentioned the speed difference might not really be there. The first day out I though I registered a top speed only 1 mph under the top speed with the props turning in. But I had forgotten to reset the "max speed" setting, so I wasn't sure. I've heard that the cats will run better in the rough, can't wait to try it. This time of the year it's tough to find - not enough boats out to chop up the lake.

Very interesting! This kind of thread is going to turn some skeptical "V" hullers into cat buyers!;)

U Ts,
I have broken vertical shafts on my outboards (TWICE:mad: :mad: ) at around 85MPH each time and like you said there is only a slight pull to that side, I think it would be worse if the prop locked up but have no idea how much.

At Havasu Sept 2000 had a pinion nut back off and jam the pinion gear but was pulling back the throttles at the time probably doing 55-60 and that prop locked, really didn't skew the boat as much as I thought it would, but I'm running with cleavers and high propshaft heights.

Caleb

Thanks Timewrap, appreciate the input

I love it! Aint it amazing when the FACTS are on your side?

T2x

PS: U T try changing prop heights....spinning out doesn't like the same water as spinning in...... also (sigh).....prop shafts should be 3 1/2 inches outboard of the tunnel wall. See ya!

t2x your check is coming next day air you should get it tomorrow
see ya charlie amann :D

T2x - Prop shaft is as high as we can get it (I'm assuming you didn't mean to go lower?). No more room for the X and we already have the IMCO shorter lowers. Prop shaft is approx 1" below the hull. The problem is, it's only a 26' Daytona, not a lot of room to move around for the twins. I'll need to check the measurement from the tunnell wall tomorrow when I see the boat.

I have a whopping 16 hours of seat time in a cat now, so any advice on driving is much appreciated!!!!!

U T, IMCO now makes a 3" shorter lower unit. There's allways something for next year.

Your the man T2x ! THanks for the info again !
I am dying to try this swap ,but I have not had mine to top speed yet because of motor problems . I will run it this way first just to see . I know it does not handle the best as is . After a few good passes I'll swap um ! My thing is I have to swap everything side for side . Motors ,trans, arnesons . I have reverse rotation motors due to old style Arneson 1600's that only turn one way . I am looking forward to trying it . Hell , I'm looking forward to boating PERIOD !!

I hope my prop shafts are in the right neighborhood as to tunnel wall !:eek: My boat has seen enogh of the circular saw and chain saw for a while !:p

U T,
I see you are turning 4,400 with the 26" props, why would you try 27" ? this will lower your rpm to 4,200. ? The center of your prop shafts are 1" below the bottom? seems very low to me, I would think you would want to be 1 or 1 1/2" above
Philip

I have a 28' Daytona and saw less than 1 mph difference between runinning the props in or out on the same afternoon with the same conditions. The boat does lean in on the turns and turns a lot better with the props spinning out. I do get a little hop around 75 with them running out, but it quits at 80 and if I bring it back down to 75 after being at 80 there is no hop.

I did have my port motor quit from a loose wire at 90 and there was very, very little pull to the side. I brought the boat down to 40 on the one motor and tried to restart the dead one, but no go, I ran the boat 5 miles to the marina on one motor at 40. I didn't want to stop and have to idle all the back if I could stay on plane without any handling problems.

Good luck with your test and be careful.

Philip - I'm just back in the office after being at Havasu and still trying to get caught up. I was going to send you a private response and let my prop thread die a natural death, but then I thought, what the heck - back to the top (TTT).

I have talked to a handful of experts on the prop issue. They all think the three bladed 27" will be the closest and worth a try (actually, one suggested a four bladed 24"). Mark at BAM was kind enough to spend time with me on the phone and after doing his science, that's the prop he came up with. I'm certainly no expert, but what I have picked up so far is, the four bladed 26" just has a lot more metal hitting the water and I guess, a lot more drag. Therefore, the lower rpm. When I tried the three bladed 25", I was all over the rev limiter. Had to bring the throttles back two inches before the rpm would come off. But as I am learning the hard way, the only sure thing is testing on your own boat. Certainly would enjoy more input.

I agree with you on the prop shaft height. But that's as high as we could get it without doing the super mod to the engine hatch, i.e. that's the highest X we could get with this boat and the twins (remember, this is the first 26' Daytona with twin engines they have done). I went with the two inch shorter lower from IMCO, but now I hear they are coming out with a 3" shorter lower. Typical! Although, I don't understand how they can fit the typical prop diameter with an additional inch shorter lower. Oh well, if they work it out, I guess I'll have to try it. I'm already down a convertible and a diamond tennis bracelet, what's one more bobble for my wife?

Hi UT,
I see, the 26” props you are running are 4 blades, and you are going to try 27” 3 blades? If that is the case I agree, the 3 blades will spin more RPM. Usually the 4 blades run smoother, are better balanced. But the 27” 3 blades might run more RPM and more speed. I have the same question as you about the 3” shorter drives. What is the largest Dia. These drives can run? And what Dia prop are you running now?
Philip

UT

Here is my workbench take on props. Only your testing will tell. I think since you said that the 3 blade 25 would not grabe taking off you are still going to have that problem with the 27 3 blade. My 2 cents is on the 4 blade 24 bravo. So I guess this means I go along with one of the experts, but am in th minority. I guess we could take a poll on this new board?

I though you were going to put whipples on? Once you do that you get to start all over again trying props.

On turning I am going from memory now since I have not been in boat in 4 months, mine sometimes leans in & sometimes out on turns. I think it leans in on lower speed turns & out on high speed turns. Of course when it leans in the higher speed turns I am thowing somein the back or front around.

Hope to get back in water next week. Picked motor up tonight, installing prochargers & other misc., taking to Owens for dyno first of week & in boat for next weekend.

Turbojack - Good to hear from you again, where you been? I hear you on the 24" Bravo and getting on plane. I was torn, but it made sense to me about the extra metal in the water. Already giving up some speed (maybe) by turning the props out. Guess the answer is to get on with installing the Whipples and just power through all this. But I am enjoying the process, and later, once the Whipples are on, I get to go through it all again. I've got some 26' Daytona driving questions for you, but I am getting hungry, so I'll post that story tomorrow.

I am running four blades on my cat because the Mirage props blowout getting on plane and in turns. But the three blades are faster, more diameter on the three blade is what I would really like to try. But the only Mirage prop with more diameter is the 29 Mirage Plus with 15" vs. 14.5".

I spin 28 Bravos to get 82 @ 4800. Before I raised the drives 2" Mirage props worked fine and I was spinning 27 Mirage Plus to get 80 @ 4800. I don't have enough power to spin the 29, but with Whipples you definitely should.

props in-out
 

In responce to your testing , props turning in, turning out

When you have the props turn in the tail of the boat lifts therefore giving greater speed but poor handling because the stern is lifted and the bow lowered, the opposite is true when the props are turned out. The tail of the boat is set allowing the bow to lift. This why the boat turns better.

rbtnt - Thanks for the story, glad to hear that an engine quitting at 90 mph doesn't cause a catastrophe. Never thought of trying to continue at speed once I shut one down. Will try that. What kind of boat did that happen on?

Anyone know if any prop shops will be at the LA Boat Show? Wish I could find a good performance shop I could work with on this. It would be nice if you could make an agreement to buy from a shop and they would let you try different props until you get the right one and then they would blueprint them for you. Any advice?

Uncle Toys

It was a 28' Daytona High profile