black hawk drive help

[craigdskilling]

Just installed the bh on a 18 donzi.I hope this works it's at 16.5"I now the magic spot is 17.5 so I hope it will work.

[MOP]

I know you will love the drive, the handling and cornering is very much improved. Will keep an eye out for your post on running it. Phil

[younger]

Your 383 is making good power and the drive may not be perfect but I have found that you can compinsate with power some. For example my setup of the drive is similar, and when I bolted it on in place of the alpha I gained 11 mph and major handling. Some of the things that are draw backs are that the boat is no good for skiing, tubimg, etc. It also works best at 50+ mph. My fuel economy also increased. All you hopes and desires will be awnsered when you hit the water. Don't get turned off the drive on your first ride. These dirves require some different driving tactics then conventional.

[Greg Guimond]

younger, you actually get better gas mileage with that set-up? That is a pretty cool side benefit :yes:

[younger]

It is not always about top end. Yes it is impressive to run fast, but I have always setup to be effeicent with that comes speed. When running my holley 750 vac I usually have the secondaries open around 4000, so I get some impressive mpg. With my 850 barry grant not as good but pull a few more rpm on top. Last season we ran 120 gps mile an burned 120 dollars in fuel. That was all day running. I think at one time I would have spent that at the bar in a few hours.

[craigdskilling]

The drive is on let's go boating anyone.I was worried how the drive was going to shift into gear from what i read,but mine shift's no problem or is that because it's not in water.i was expecting clunks.:nilly::nilly:

[MDonziM]

Mine shifts smoothly and since I go about 7 mph in gear the shifting is constant in no wake zones and around the dock. Keep us posted on your performance.

[MOP]

They do shift quite a bit different in the water, at dead idle they run faster than most wake zones allow. Where I knew it was strict I would run the tabs full down to slow it up a but. Cruising fuel consumption is amazing, the drive seems to have very little slip at cruise using a lot less fuel then my current Bravo X.

[MDonziM]

They do shift quite a bit different in the water, at dead idle they run faster than most wake zones allow. Where I knew it was strict I would run the tabs full down to slow it up a but. Cruising fuel consumption is amazing, the drive seems to have very little slip at cruise using a lot less fuel then my current Bravo X.

Phil,

I have not run the numbers lately but the slip% curve is different I think, rather than more efficient. At top end I think my slip is 12 or 13% vs 8-9% with my bravo drive and mirage+ prop. (These #'s are from recollection) But at 3500 rpm or so it does seem efficient or perhapps, more efficient.

Anyway, your old drive has held up well, only oil changes so far...( knock on wood) with about 75hrs.

Thanks - Marshall

[MOP]

On mine at cruise it held the bow at a decent angle had great bite which gave good gph figures, at higher speeds the boat flattened out I just did not have enough ponies and sucked fuel. The swap to the Bravo X gave me about 7 mph, that gave me the trim very much needed in a 22. I still miss the drive and am sorry I let it go, the lack of prop torque and handing is sorely missed. If all I did was got to about 4,000 it would still be on the boat, shame we get so caught up in the final figures and not in what we do the most of.

Phil

[craigdskilling]

I should have the ponys with the 383 400+ to make work well.I have a swim platform on the back that shouldn't make any dif.I will get some pics up this weakand.

[yeller]

The drive is on let's go boating anyone.I was worried how the drive was going to shift into gear from what i read,but mine shift's no problem or is that because it's not in water.i was expecting clunks.:nilly::nilly:It will shift differently when in the water. Mine is smooth out of the water, but a bear in the water.

Mine shifts smoothly and since I go about 7 mph in gear the shifting is constant in no wake zones and around the dock. Keep us posted on your performance.I wish I knew what the difference was between our setups. I can get it into gear and out of reverse fine, but getting it out of forward is a major PITA.

[MDonziM]

Yeller,

Don't know what the difference might be... My hull is a 94'. I have my eng idle lower than my engine guy likes (maby 850-900 rpm). I did change my throttle to a Dana 2 lever which I love, effortless throw. My biggest pain with shifting is with my 31" props my rpm dips to 500-600 when I put it in gear which is obviously close to stalling, but I only stay there for a second. If you want to talk you can call me 516 286-6131.

- Marshall

[craigdskilling]

Hey guys here are a few picks of the drive on.my boat is a 84 classic.I notice the round bottom to a step hull. is this going to make a difference.I was able to use my old drive shower just mod a little.something is better than nothing to cool the top of the drive.

[MOP]

Have you carefully timed the props? If unsure of how read the post below, the props should be silent a speed no HUM whatsoever!

http://www.donzi.net/forums/showthread.php?t=62107&highlight=prop+timing

[craigdskilling]

MOP what are you saying.The props i got came from the the original box.It said to have the front prop off centerd to the back.At low rpm out of the water no problem.Can i hear this hum out of the water.Now i'm freaking out.:shocking:.Please help.Should i put a vid up with it running.

[LITTLE MAX]

Check you pm

[gero1]

i have met mel in wi a few times and he showed me how to time the props the way they did it during testing. on a black hawk boat they will hum, its a beautiful sound....the sound of speed

[younger]

The front prop feeds the rear prop, they need to be timed so the water comming off the front prop is pushed into the path of the rear prop. If the timming is out, the water off the front prop blade entering the water will push the thrust water into the front side of the rear prop blade causing a loss in performance, humming vibration. With most surface drive apps you will hear the prop blades hitting the water, but no vibration. From my testing my hoss props are silky smooth. My timming on those is the rear prop is 1 spline counter clockwise from merc timming. There in no magic here just keep testing. What kind of performance have you seen??????????????

[glashole]

i can honestly say i have never timed my props

will try this year and I assume i will get the same results as i did by using the speed wax i bought off this site a few years back


i still have some of the wax left too over if anyone wants to buy some from me

[younger]

Shea play with the timming might be a little more. Go for the free speed.

[glashole]

thanks for the advice i will try that this year and see how I make out

[craigdskilling]

No testing done yet.Going to clean it up this weekend.I made sure that the front prop was off center to the back.When can we get together for a rip.Hay Shea can i get some of that wax:wink:

[MOP]

It would be great for a real BH tech to fully explain the timing issue, I have given it a bunch of thought. Though I know from fooling with mine it did work, it did not quite make sense looking at two props turning in opposite directions. Why does it make a difference where the blades pass each other, I would real like for someone knowledgeable to explain it. I am curious why duo boat propellers but none of the various duo prop aircraft do not need the same, I hope someone smart chimes in!

[LITTLE MAX]

Phil
Less slip = More speed :crossfing:

[MDonziM]

i can honestly say i have never timed my props

will try this year and I assume i will get the same results as i did by using the speed wax i bought off this site a few years back


i still have some of the wax left too over if anyone wants to buy some from me

Shea,

Thats funny. I have tried moving my small prop 1 spline this way or that way and never seen/ felt a difference either. ( I did pick up 7 mph with that wax though) If you look at the 2nd photo it looks to me like the props may not be timed right but its hard to tell when the big prop doent have a blade at 12:00.

Craig - post a pic with the big prop blade strait up.

- Marshall

[MDonziM]

It would be great for a real BH tech to fully explain the timing issue, I have given it a bunch of thought. Though I know from fooling with mine it did work, it did not quite make sense looking at two props turning in opposite directions. Why does it make a difference where the blades pass each other, I would real like for someone knowledgeable to explain it. I am curious why duo boat propellers but none of the various duo prop aircraft do not need the same, I hope someone smart chimes in!

One thing to keep in mind here is that we are talking about the bh propeller efficiency/ slip etc with a different x-dim setup than it was designed for. I don't know for sure but I think that the timing relates to the big prop blade at 12:00 because in a real bh setup at the top of the rotation the blade is partially out of the water. There is some airation affect with the counter rotating props that is partially lost, I bet, with our stock bravo deeper x- dimension setup.

[younger]

When I was looking for prop help I contacted Dave Bostic at Hoss and we talked for hours about x-dia., prop design and timming. What a great guy. As a surface drive the props only make sold contact with the water on the bottom of there rotation. That is why the front prop feeds the rear on the bh. The front turning left ideally makes contact at 9 oclock and pushes the water to the rear to feed the right turning prop. If not timed the props start to loose effeicency. I have looked at the props at speed and they are in a whirl of water and air. It would make a cool vid. Craig get the boat in the water and test! test! This will get you a solid start in what direction you need to go. If you hit the mark the first time a-men!

[MOP]

Timing is done to all dou drives not just BH's! Merc III's and Volvo's standard X mounted drives, it is in their manuals. Timing has nothing to do with the X, there is a resonance setup. The research it is not plug and play, so many have tried the drive but only one boat Steve Mars was setup correctly and boy did it show! Steve's 18 with a stock 300 Merc it ran just shy of 80.

[Ghost]

If it's what I've heard of before, it shouldn't be trial and error as much as just setting things to a known relationship. I thought the duoprop was supposed to have one prop with a blade centered at 12 oclock, while the other prop had blades evenly split at 10 oclock and two oclock.

Right or wrong, this relationship should be pretty easy to set up, no?

For clarity, is anyone talking about something other than this setup?

[craigdskilling]

63663

63664

63665

63666

63667Here is some picks.I put the red tape on were i was told to set them up at.the back prop should be 12:00 at the cutting edge and the front at 4:30at the cutting edge then when you spin the props you should have clean water pushing on both props at all time.I was given these # by a member here thanks i hope they look right.Could you let me now if it looks right.

[LITTLE MAX]

They look about right to me.

[craigdskilling]

I will be going out next with a 28 zx donzi all done up should be fun.I will get some gps # and vidio.the picks of your45 big max is great.thanks craig.

[Ghost]

If it's what I've heard of before, it shouldn't be trial and error as much as just setting things to a known relationship. I thought the duoprop was supposed to have one prop with a blade centered at 12 oclock, while the other prop had blades evenly split at 10 oclock and two oclock.

Right or wrong, this relationship should be pretty easy to set up, no?

For clarity, is anyone talking about something other than this setup?


Here is some picks.I put the red tape on were i was told to set them up at.the back prop should be 12:00 at the cutting edge and the front at 4:30at the cutting edge then when you spin the props you should have clean water pushing on both props at all time.I was given these # by a member here thanks i hope they look right.Could you let me now if it looks right.

Taking a stab at answering my own question. Sounds like this IS different from the Volvo Duoprop recommendations I have heard. Those are, I am told, intended to keep the blades from crossing at 12:00, directly below the cavitation plate.

The Blackhawk recommendation above sounds like it is not concerned with the blades' relationship to the cav. plate (all of which are mostly out of the water up there anyway, right?) and instead is about the arrangement of the blades down in the water.

[younger]

That is idea with the surface props, do most of the work on the bottom part of the arc. If a bh is set up right with the proper x, the top of the props under the cav plate are airaited. On the bh the rear prop runs more airaited then the front. The front feeds the rear.

[craigdskilling]

Took boat out ran great.Had it up 75mlp with it still going strong.Rpm at 5500 with 27s but stoped to check the engine comp to see green gear oil in the hull. Can't see where it is coming from.So that ended that day:confused:.I dont think anything happened to the drive it feels free spinning no grinding.Help

[glashole]

i have seen drive oil get pushed back into the overflow bottle after some hard running

if the overflow is to full it will come out the top

hopefully this is your issue

Shea

[MOP]

Could be the plastic oil line connection nipple inside the transom, it is a pain to change with the engine in.

[Ranman]

I had a similar issue with gear oil in the bilge. I thought it was the gear lube nipple as well, but that wasn't it.

In my case the input shaft seal on the outdrive was bad due to a loose input shaft spanner nut. When the seal fails, the gear lube bottle keeps feeding the drive and the fluid leaks through the U-joint bellows and into the bilge. Not a tough fix but you should pull the drive to see if there's gear oil in the bellows to confirm or rule out the input shaft seal.

[craigdskilling]

I looked into it a little more when I got home and i didn't put the over flow hose on tight on the drive.No damage to the drive.I only lost a litre or so.It was fun with that drive on but i think i need some 29 to bring the rpm down to5000 or more.

[LITTLE MAX]

I looked into it a little more when I got home and i didn't put the over flow hose on tight on the drive.No damage to the drive.I only lost a litre or so.It was fun with that drive on but i think i need some 29 to bring the rpm down to5000 or more. Craig if they are stock 27 put the max cup in them that should knock down some rpm for you

Glad you like the drive

[glashole]

drive to trenton and you can try a set of 29's and see if they will work

[younger]

I'm in! If you guys are up for some prop testing lets get down with it. If I remember that Murry canal is good for 80.

[craigdskilling]

Hey guys hope everything is well.I would love to get together when i get it running.What a ride with the bh i find that my trim tabs dont do to much anymore but really solid.I found that when i was going full out that i brought thedrive up just a bit is that bad.It was still climbing up on the gps at 75 with a full tank and two guys.I hope that by the end or middle of june that i should have some time or give me some dates that work with you guys.thanks craig.

[glashole]

with some heads up I am generally available

bring beer

[craigdskilling]

In the end june looks great.I'll come up on a Friday and stay over and do some boating all day sat show me around.I was thinking that i have use of a cottage any time in the kawarthas.get you and younger up there for a weekand.