BlackHawk drive aeration tube

[yeller]

I've read about others that have added an aeration tube to their BlackHawk. From what I've read, the air sucked in by the props, reduces the torque load on the drive when the props are submerged and this can result in easier shifting and reduce idle speed due to increased prop slip at idle. It can also reduce planing time by allowing the motor to build rpm faster.

I don't have the latter problem, but shifting is a PITA. I wouldn't mind a reduced idle speed, but the shifting issue is the main reason I'm going to try an aeration tube.

I bought a length of 2"OD aluminum tube and marked the cover plate where I wanted to install it and cut the hole.
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Then I cut through the cavitation plate.
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...and then through the anode that mounts to the underside of the cavitation plate.
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Here's a look of where the air will enter relative to the props. In the 1st pick you see the blade of the front prop through the holes. In the 2nd pic, I dropped the tube onto the prop to get a clear image of where the air will hit the props.
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I briefly debated on adding a support bracket, but it looks ugly as chit and I determined it's not need structurally, so I'm not going to bother. (I just have to keep people from using the tube as a grab handle when climbing up the drive).
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Here the cover is prepped for welding the tube. The tube will be welded to the top cover only and it will protrude enough to fit to the bottom of the cavitation plate hole.
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I'll post a pic when the tube is welded in place, and if I ever get the boat on the water again, I'll cut the tube to the proper height...and update on the results.

[glashole]

if the gears are set up properly as well as the shift plate it should be smooth as silk
you might want to get someone to reset it up if there is an issue or it is really difficult going into out out-of gear

obviously its a bit late for that now but you might still want to look into it

Shea

[yeller]

Thanks Shea.

On a BH specific boat, you are correct, it will be smooth as silk. I have read, that BH boats have the ECU programmed to assist in shifting. I believe a programmed ECU will allow for a lower idle without letting the motor die when dropped into gear. Without that programming, the idle has to be set a bit higher to prevent the motor from stalling. This is just what I read somewhere.

My drive does shift fairly smoothly when the props are out of the water, but once loaded, things get very difficult.

Yesterday afternoon, I did pull the top end apart and can tell that the gears exploded at some point in its life, so it is rebuilt. The Merc manual states that if newer gears/clutch are installed, the latest shift mechanism must also be used and old/new style should never be mixed together. I haven't confirmed yet whether all the correct parts were used. The shift cams are the new style, but the shift "fork" is suspect. There is noticeable damage to the cone clutch and they need to be replaced, but I don't know if this damage is from my use, or was there when I bought it. The drive came directly off a Donzi BH boat and the seller said he had no issues with shifting. There is no way to know for sure.

It's entirely possible that changing the clutch would eliminate my problem, but I'd hate to put it back to together and still have an issue, so I still want to try the aeration tube. I don't see any downside to the tube whether it's need or not, so I figured why not. It's a pretty easy project and if I ever wanted to eliminate it, the repair would be easy.

[craigdskilling]

My boat use to have a alpha drive and when I changed to the Blackhawk I read that they were very hard around the dock but I have no issues now I don't now if it's because I kept all my alpha micro switch and throttle body.Even when I put the new motor in which is efi I still kept the old in that micro switch acts like a kill switch in and out of gear just my 2 cents.Good luck bud.

[VetteLT193]

The aeration tube, from a logical perspective, will do very little when shifting. It may let you set idle down a tad because the props may get to moving a bit faster but minimal I'd think.

It will help the most when the props are spinning the fastest while still submerged. You may end up liking it for other reasons regardless. I'm thinking something else is off on your setup. What does it do exactly? Is it physically hard to get the shifter to move or drop into gear?

[yeller]

The aeration tube, from a logical perspective, will do very little when shifting. It may let you set idle down a tad because the props may get to moving a bit faster but minimal I'd think.

It will help the most when the props are spinning the fastest while still submerged. You may end up liking it for other reasons regardless. I'm thinking something else is off on your setup. What does it do exactly? Is it physically hard to get the shifter to move or drop into gear?Drive goes in/out of fwd/rev no problem when out of the water. When in the water, drive goes in/out of reverse no problem and into forward easily. It is getting out of forward that is the nightmare. I have to repeatedly yank on the shifter to get it out of gear.
When I tore apart the drive, I found one of the brass rings for the clutch was badly gouged. I don't know if that was there when I bought the drive, or happened afterwards. I've only used the drive for a couple hours and it was a pita shifting the whole time. I've swapped the entire upper assembly from my B1x and I just need to set it properly. Hopefully that will solve my shifting issues.

There was a guy on PerformanceBoats that did the aeration tube on his BH and he said it helped his shifting somewhat, although his main reason was to help reduce planing time, (which it did significantly). I mentioned earlier that I don't have a problem building rpms when getting on plane, but I forgot to mention that I do have an excessive planing time. Although I can put as much power to the drive as I want (when getting on plane), I keep it to a minimum to prevent excessive torque on the drive. If the aeration tube reduces the torque load on the props and allows me to add more power to reduce planing time, I will be happy with that.

[RickSE]

You may find that you'll have to feather it up on plane a bit with the tube. I'll be interesting to see if this is the case with the surface props. Does the BH run any exhaust through the drive/props? I'm thinking it doesn't. Looks good Glen.

[yeller]

I do have switchable exhaust, but it doesn't connect to the drive with an exhaust bellow. The exhaust would airate the props when it exits the transom and the tube I'm making may be a total flop, but I won't know until I try it. It's a super cheap experiment and if I don't like it, all I have to do is fill the hole and repaint the cover.

This is from a posting from someone that did the tube. Different boat and different reasoning for using a tube, but it got me interested in trying one nontheless.
When I first installed a BH drive on my 25 Daytona with a stock 500efi, planing the boat off was very tough with any more than 2 adults and 1/2 tanks of fuel. Because the drive was originally designed to have the exhaust exit thru the drive infront of the props and my boat had straight thru hulls, I had an "issue" .

The load of twin 31 pitch props would prevent the engine from reaching a decent section of its torque curve and it would lug along firewalled at 2500 rpm for what seemed like ever before forward speed would help unload the props allowing the engine to spin up over 3000 rpm and eventually plane off. I even twisted the splines off the vertical shaft once due to torque loading.

My solution was to fabricate and install an internal airation system. I had done some rubber tubes on another boat for a friend. Functional but fugly. I wanted something that looked more finnished. Once completed, it allowed the boat to plane off much easier with far less throttle, even with full tanks and 5 passengers. It lowered the dreaded BH idle speed 2mph and and softened the shifting as well.

[yeller]

Tube is welded in place and painted. I'll probably end up cutting at least 6" off, but I need to get the boat in the water 1st to decide on the final height.

[yeller]

Here's a pic of the inside of case, which clearly shows that the gears exploded at some point in its life.
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...and pics of the clutch.
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The upper gear assembly had been updated to the BravoX gears. They are the same as in my B1X drive. I'm also swapping over the drive shaft from my X drive so I get the advantage of the larger universal joints.

[yeller]

To swap the gears over I needed two different spanner wrenches to remove the retainer nuts. I couldn't stomach $200 for a single wrench, so a grabbed some scrap metal and made my own.

For the BlackHawk
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I was much less enthiastic about making the next one. :biggrin.:
For the Bravo1x
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[RickSE]

If you want, send me some dimensions and I'll make you a CAD model and drawing for them.

Are you coming down South at all this year? We picked up a new tow rig and are headed over to Vegas this weekend, then we go back at the end of summer. We haven't used it for the boat yet but hope to take the rig and the boat up to Powell later this month & just stay in the campground.

[yeller]

Holy crap Rick! Now that's a tow rig. :eek:

We're going to just miss you at Vegas. We'll be there the next weekend.
I'd like to get to Powell this year. Would like to be there for the Powell Challenge, but I've cancelled too many times to say I'll be there. It's tripled in price, so don't think I'd sign up anyways.

Thanks for the CAD offer, but although the wrenches don't look pretty, they work.

.....and at least I have a good excuse for not using my boat. :wink:

[RickSE]

... It's tripled in price, so don't think I'd sign up anyways...

Wow, I hadn't seen that. There's no way in heck I'm going to pay $500 for a Poker Run then burn $500 in fuel. Guess they priced us out. :frown:

We'll be going through Vegas the following week. If all goes as planned we'll pass through on the 12th on our way to Top Gun Raceway in Fallon, NV. Then we come back through on the 14th. We won't go back to Vegas until Sept and then race there three weekends in a row.

[Lenny]

Glen, I bought Mike Miller a BH wrench as a "gift " when he got his BH boat a long while ago. He might still have it.

As for the height of the Aeriation tube, I think you should leave it there and hang a Canadian flag on it... :)

Interesting project

[RickSE]

...I think you should leave it there and hang a Canadian flag on it... :)...

Or use it for an umbrella mount.

[yeller]

We'll be going through Vegas the following week. If all goes as planned we'll pass through on the 12th on our way to Top Gun Raceway in Fallon, NV. Then we come back through on the 14th. We won't go back to Vegas until Sept and then race there three weekends in a row.Will you be stopping in Vegas? We arrive on the 13th, so we could meet up. Even if you just plan to stop for a bite to eat, let me know and we'll meet you there.


Glen, I bought Mike Miller a BH wrench as a "gift " when he got his BH boat a long while ago. He might still have it.

As for the height of the Aeriation tube, I think you should leave it there and hang a Canadian flag on it... :)

Interesting project
Thanks for the tip Lenny....but as you can see, I already have a couple beautiful wrenches. :biggrin.:


Or use it for an umbrella mount.
Flag, Umbrella, or just plain air tube? What to do...what to do. :confused:

[glashole]

the bravo X gears are the way to go for sure
In my opinion I would still do slow starts when getting on plane because it puts less stress on the drive.

if you are concerned with racing your buddies then just make the races longer and pass them further down the lake

there is a guy in canada north of toronto who can set the drive up with your gears and has all the equipment - he isn't cheap and I know a major member here has a bit of an issue with him but he worked wonders on my blackhawk

good luck with the tube - looks good

Shea

[yeller]

the bravo X gears are the way to go for sure
In my opinion I would still do slow starts when getting on plane because it puts less stress on the drive.

if you are concerned with racing your buddies then just make the races longer and pass them further down the lake

there is a guy in canada north of toronto who can set the drive up with your gears and has all the equipment - he isn't cheap and I know a major member here has a bit of an issue with him but he worked wonders on my blackhawk

good luck with the tube - looks good

SheaThanks for tip Shea, but Toronto is too far from me to ship the drive for a gear set up. Now if Ed would go west once in a while instead of always going south....

I'm with you on the starts. I always take it easy out of the hole.......and I like speed, but not really concerned with racing anyone.