prop torque
 

Brad at bblades has been helping me figure out my prop slip situation. Started with a 30p B1, had 26% slip went to a 29p hydro P5 5 blade. Still at 20% slip. Im already running a 1" drive spacer. X dim is 5 1/2". My boat prop torques to the left pretty noticable. (Leans to the left). Brad wants me to run 2" of spacer. I beleave that will make my boat torque. To the left even more so. Thay just sent me a 28p 15 5/8" diameter mercury maximus 5 blade. Ill be testing with it tomorrow in hopes that it gets my slip % down in the mid teens and hopefully my top end up to 80. If i do have to go with more spacer will it get my lean on more than it already does.

i think the 1 inch spacer will help with the slip...but what do i know?...keep us posted,josh

fixx
 

smaller diameter will give you less twist on the boat..do you have a low water pick up??also you should be runninf a rt hand prop not a lefty,,that is probablt where the torque lean is coming from..espicially if your steering wheel is on the rt side..also put a straight edge on the last 8' of the hull and look for a hook..

Im already running a 1" spacer. Thay want me to add another inch to it. And i didnt know you could change the direction the prop spins. Mine is standard like every boat ive had. If your standing behind the boat the prop spins clockwise. Ive never seen any different on a single engine boat.

Maybe Transom/Stringes have some waterlog issues? Will produce Slip.

no waterlog issues here buddy. this boat is like new and in perfect condition. it never sits in water overnight and is garage kept at all times. Just got back from testing that new prop. thay can have it back. lost 6 MPH and was only turning 4600 rpm. guess thats one way to get my slip down. LMFAO!!! crazy thing is it blows out at 3500 and then bites back in when the front end falls on plane. I def liked the Hydromotive P5 better.

What rpm and speed were you running with the hydro?

5000 and 73. Thies are all GPS speeds not the wishometer. If i could get the hydro to hook up id be pushing 80.

It seems like you would want a smaller OD prop with more blade surface area. Keep us updated on the search, im still trying to find the right setup for my SCS.

I agree. maybe i should try the 6 blade herring thay have. 2 grand. #@$%!!!

Hi Josh,

I know trying to dial in a boat that has issues can be rather frustrating. Especially when you are starting from scratch. You have a issue that you can't figure out. We are just here trying to help you through it. We are only as good as the information we are supplied. I always wish I could be in the boat with you. That way we could help each other get to the finish line faster.

Remember, boating is supposed to be fun.

Your slip is high, your boat atitude is less than desireable. When you say "they want me to" you are being a little over zealous. Suggesting lower "X" dimetions is not saying we require you to do that, we are giving you options as to the problems your boat might be having and the physics that can correct that situation. Boats are tough. Many variables. Each change in singular order helps us to learn and move in the correct direction.

Less diameter will definately adjust the boats list (decrease it) more but less diameter will not aid in your slip number unless the diameter changes are sustantial enough to create big transom lift and drive leverage changes. I agree the depth of the propeller isn't high. But, the slip is still high. Why? Trying to harness the slip is the first move. Could going up in X help, maybe, probably not. Do you want to buy a short drive to do that test? Thats why we went to bigger diameter 5 blades to troubleshoot.

fixx, RH already. Josh, we can test with either rotation.

Using stock propellers at their designed geometry helps us to get to the root of the issue.

6 blades.......don't think so. Custom 5 blades, probably. Getting to the ultimate set up can take longer with some rigs than others.
Don't worry, you'll get there.

Brett

Thanks brett. I still have a blast boating even though im not in the 80s. lol. And i know that if it can be figured out you guys are the ones that can do it. I currently have two of your props. the hydro 5 blade 29 and the maximus 5 blade 28. i got better speed but more slip 20% with the hydro and 18% slip with the maximus but lost 6mph. so im going to send the maximus back to you and keep the hydro and try 2" of drive spacer unless you have a different prop you would like me to try? I admit im a little discourage with all the $$$ ive put into this boat and ive only gained 7mph but its still fast and it runs great and has unbeleavable mid range acceleration. so im happy with that. Ill be patient as long as you guys continue to give me great service as you have been.

Thank again!!

Nice post!

The drives can run in either direction, a lot of single Fountains run with a left hand drive. If you wanted to test a left propeller you can, just shift the boat into what would normally be "R" and go....if you decide you like the left better then swap the shift cable under the shifter.

As far as the prop slip just stick with it, you will finally get there.

[QUOTE=Baja_man;3723502]The drives can run in either direction, a lot of single Fountains run with a left hand drive. If you wanted to test a left propeller you can, just shift the boat into what would normally be "R" and go....if you decide you like the left better then swap the shift cable under the shifter.

As far as the prop slip just stick with it, you will finally get there.

Thats cool. I didnt know if reverse is as strong as forward. Aparently it dosent matter with an outdrive. In a truck axle the angle the gears are cut makes them stronger rotating one direction than the other. for instance in an offroad rig you cant buy a standard low pinion axle, cut and flip the diff and turn it into a high pinion with out buying reverse cut ring and pinion gears......

I love this site. I learn something new almost everytime i log on.

That is one of the beauties of the Bravo drive. You can shift to reverse and test forward operation with a left hand propeller (or vice versa). Most other drives won't work though. Outboards will work but it isn't a good idea for more than a quick test since the engagement lugs are half of the volume that they are in forward.

Brett

I think you are fine with the gears unless there are some significant wear patterns. But, going off memory running a left handed prop puts a lot more stress on the top cap.

How much HP are you running????? It takes close to 600hp to get a 280 PQ to 80mph.

A propshaft 5.5" below the bottom should be plenty deep already. I would not be overly concerned with slip percentages within reason.
A slightly higher slip % will be easier on the drive.

It will take nearly if not all of 675-700 hp to move a 280 Silencer to the honest 80 mph mark......ask me how I know...

Slip may be easy on the drive but its killing my top end.if my drive cant handle it ill buy a imco. I spent thousands to get the power i have and i will not stop untill i see 80 on my gps.. as far as HP. Stock is 415. CMI add idk at least 50? You guys tell me. Procharger set up im running thay guaranted me 200hp gain. Do the math. 675. Its got the ass to see 80. Its all about getting the boat set up right.

IMO the headers are doing very little on a procharged engine. Have you checked your air/fuel ratios? If you're running pig rich you can knock down the hp. Adding 200hp is possible if set-up correctly, if not that 675hp estimate can easily become 575hp.

I think you may be reaching a bit expecting a 200hp gain on that setup. Unless you have dyno numbers, I don't think you can pull the ricer move and add up some advertised numbers and believe you're at 675.

Call mark at precision marine and question him. Hes the best as far as you so called experts on here say. He tuned it. So ya its set up rt. Plugs are perfect. Its not rich. And not too lean. And 575 isnt going to slip a 30p b1 and a 29p hydro p5 at thoes %s. And hell if anyone wants to trade me a stock set of manifolds for my $4000 CMIs lets do it since thats whats slowing me down. LMFAO. do you guys read this **** before you post it? Seriously? Im trying to fig out why my PROPS are not hooking up. The power is there. Its not a hp issue. Its a prop slip issue. Do you think you blow the tires off on a drag car becauae you dont have enough power? F@#k no. Its because you got too much power for whats under the ass.

In my opinion the problem is that i have one of the biggest single engine boats made. And it has THE biggest step hull of any single engine boat made. The prop is turning in the bubbles the step is making and we all know that props arent made to push air. Its obviously a boat/drive setup issue..... and juat to add to this. This setup im running has a hole shot like ive never seen. It gets on plane and breaks 60 unbeleavable in seconds.

Im gonna go to autozone and buy one of thoes cold air intakes to put on my procharger so ill get that extra 200hp like the ricers do. :lolhit:

Josh, my old 280 is now running a 675 hp 555 cu.in, and he can tap 80-81, but always 78-79, any conditions. I know this first hand because we boat together.
He runs either a tweaked 28 or 30 Bravo 1.
I'll check drive height with his. His drive height is stock as well as no spacers.
Have you checked for hull hook, just throwing this out there...
I always thought that a pro charger would give 100hp...but what do I know....

I base that comment on my personal setup. '97 MPI, 731 Crane cam (huge improvement over stock,) Dart 308s (mild improvement over stock,) Stainless manifolds (not holding any power back at this level,) stock everything else with an M1, and I'm not making 675hp. If I were, my little Fontaine would be running 90+. 5lbs is good for 100hp. 7lbs, maybe another 25? I stick by my comment...unless you have dyno numbers, you don't know how much hp you have. Period.

For drag cars.... Just like you're trying to prove on your boat, setup is everything....not power alone. HP has little to do with blowing tires vs chassis setup.

Not bashing you at all and am actually quite interested in your problem. I've recently made significant X and prop changes to my boat and am following the general practice of moving the drive up, not down. I also don't believe in the premise that just because someone else made a boat run XXmph with some hp and a prop that it should be able to be done to a sister ship, "because Bob did it." Every situation is different, no matter what. I wonder..... have you looked over your running surface with a straight edge for a hook or checked for any other anomalies that may be allowing more air?

For a rhetorical question, at what point does one realize that no matter how much money is thrown at a project, some things are just not meant to do what one is trying to get it to do? Sometimes you have to throw the towel and move on to a proven setup.

What's your next move, space it down?

Josh, have you run the boat without the 1" drive spacer?
whats the history of the spacer, why was it put on??

I think your last comment of it having a great hole shot says two things. 1 power is crazy because you would have snapped your drive by now. 2 a boat really set up for big top end takes a little to get on plane with out using tabs. Thy typically cavitate and slip with because of high x dim and can be a bit of challenge getting on plane.
You need to baby the boat up on plane or you will be replacing drives. Thu just don't like being hammered like that. No drive does.
You also need to pull the spacer and raise you x up and see if that helps. Should reduce torgue roll and gain top end. You will of course have to re prop to a bigger pitch to hook up and being the rpm's down. If it doesn't then go down even more. Will get slip numbers down but you may lose some speed. Also slip numbers can be fudged. People tend to over trim and get bad numbers. They test where how should and slip numbers are better but speed is lost so they dont like that answer and go back to over trimming when the answer is to get te x up.
I run a 30 stepped v single and have been through all this. It's a pain but it's trial and error.
It's frustrating to say the least because sometimes the experts answers are not correct for your set up and you feel like they give up on you.
You will get there... Eventually lol.

I was just trying to help. Being too rich will knock the hp down. I didn't realize that Mark tuned the engine in the boat with his laptop and a air/fuel meter.

Many times people think they have more hp than they actually do. So they put a bigger prop on and over trim it to get the rpms they want. What happens when you over trim your drive? Prop slip goes up. If it were me I would put on a smaller Bravo prop and see what kind of speed and rpms you get. Quick and easy and points you in the right direction.

And I never said the CMIs were costing you hp, I was merely stating that you get less gains on a SC engine. On a NA engine with bigger cams they make more of a difference because they scavenge better than stock exhaust.

Comparing a boat prop to a drag car's tires is like comparing an apple to a dog turd. But it sounds like you have it all figured out.

I've talked to a boat racer that has been in a tight competition with another team. Then he discovered that the other teams boat ran into a wall at 89mph. They could add more power but it didn't want to go faster. At this point you have to examine everything with a magnifying glass. It is going to take a lot of patience, you may be at point in the performance in your hull that may take a large bump in power to cross, or you may have some unusual anomaly that is peculiar to your boat. It is going to take time and attention to detail, create a log of each trial. I know I'm in the same situation, I'm running high 80's and want to break 90. Are you running a stock Bravo lower? I added a Hydro-Motive nose cone and it was one of the best things I did. Boat handles much better at WOT and takes more trim.

That is the best un bias advice ive gotten on here other than from BBlades. Thank you for not being a negative ignorant opinionated idiot that prob pays somebody to change your oil in your boat.. i love thia site but i twnd to get alot of advice from back yard hac

Hack artist that jump off topic and sont really know what thay are talking about. It wears me out.....

.....must be the headers thats slowing you down. What the **** ever. Lmfao!

i feel your pain..i been going throu more or less same thing with my avanti. first was up with a 2" imco lower,then was back down.then back up because wrong prop. then slip was to high but was running decent mph. then i put imco extension box on with the box i also raised engine 3".so now im 5" higher and i guess a foot or 2 farther back.im still playing with props and but also goin to try bringing drive down for less slip.goin to start with 2" spacer and go from there.i am very happy with my ext. box and also raising engine and drive 3" when installing box. good luck
mark

Ive thought about an extension box to see if it helps.

No one said the headers are slowing you down. I merely stated they're not giving you 50hp and they make a bigger difference on NA engines. I was just trying to help and you jumped on my statement.

Prop slip somes from hull design, propshaft depth, etc, not just hp. Plenty of people running 3 blade props with 600-700 hp with low slip and high speeds. How can they do it? With all that hp they should just blow the prop out just like a drag car blows the tires out and have 30% slip???

Im convinced that it has alot to do with the design of the hull. With in turn makes drive height and other prop situations more critical. The research ive done has proven to me that non step hull boats typically have less slip % than step hull boats. So my main concern ia to find a way to get clean un disturbed water to my prop at WOT. When amd if i can do that my slip % should drop into the mid teens and what ever speed im running at that point is what ill have to deal with.

At what RPM is your boost coming in? That is a good reference to look at when trying to find the correct prop. I have had two boats with prochargers and big HP. I am in Indy and have a few props you might want to try. Just give me a call and I will tell you more. 317-679-4453 Mike.

Hey dip ****. I was the dude you hung out with at cunninghams sunday. Lol. Small world huh. We were both drunk. Atleast i was but i rememberd your blue led s. Cus i got em too. You gonna be down this weekend.

Not coming down this week but I am sure I will be down soon. When does your boost come in? In my experience, if it comes in before 4000 rpm I was over proped and very much after I was under proped. Call me and when I come down next time I will bring some props for you to try.