Aluminum Driveline?

[2112]

Anyone out there swap out the heavy steel Merc driveline for an aftermarket aluminum or even carbon fiber driveline?

Seems that they have been race proven in many other arenas and in my boat, it is a straight line application, no angle at all. Could probably even eliminate one of the u-joints.

Any opinions out there?
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[Sean H]

yes. carbon will survive moderate power/not to rough/not to big of boat.

nothin beats a steel one in big power/big water conditions.

 

[2112]

Is there a reason to have a slip joint in the driveline if the distance is fixed length?

How about a u-joint on each end if there is zero angle? Both Needed?
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[phragle]

the probability of actually having a dead nuts zero angle is slim multiplied by any flex... you may get it close enough to live but it will fatigue and crack eventually unless you are running a rubber coupler. I have seen video of a boat running hard without the engine hatch... the motors move.

 

[2112]

I do have rubber couplers...Bravos.

Not perfectly zero. There is approximately .005" of "pivot" of each u-joint in a complete rotation. I am just wondering if 1 u-joint is enough.

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[phragle]

are you attempting to gain something by eliminating it? the actual mass given the diameter is fairly small....

 

[MikeyFIN]

Anyone out there swap out the heavy steel Merc driveline for an aftermarket aluminum or even carbon fiber driveline?

Seems that they have been race proven in many other arenas and in my boat, it is a straight line application, no angle at all. Could probably even eliminate one of the u-joints.

Any opinions out there?
.

Yes.
I don´t see the gain there..except bling factor if you polish one.

 

[Ratickle]

Weight is weight.

I don't know for sure what they ended up doing, but if you get ahold of Keith with the Cat Can Do team they use aluminum in their Super Cat/PX Cat. It broke at St Clair this year, but they had it repaired and they ran fine. The new blower motors they run have a lot more power than the old SuperCat engines use to have, so their opinion should be a good one. CK Motorsports in Spring Lake, MI. Keith Holmes. Plus he's a certified Mercury Mechanic on the big drives.

 

[DAREDEVIL]

Is there a reason to have a slip joint in the driveline if the distance is fixed length?

How about a u-joint on each end if there is zero angle? Both Needed?
.

U don't whant 0 angle.

best for a drive shaft is 2-3 * !!!!!! And a slip joint is a must due to vibration !

 

[imco offshore]

U don't whant 0 angle.

best for a drive shaft is 2-3 * !!!!!! And a slip joint is a must due to vibration !

god knows i hate to say this,,, dd is right,,,damn it,,,, you need at least 2 o of angle in a u-joint so the needle bearings inside the cups will rotate , otherwise they stay fixed and pound flat and vibrate and blow out, those little needle bearings spin in the cup and reduce friction.(hp) and i did see carbon fiber driveshafts yesterday on 700 hp and a 39' boat ,,,:USA: god please save me.....lol

 

[Sean H]

Yes.
I don´t see the gain there..except bling factor if you polish one.

there are big gains in race setups with long driveshafts (cats, full staggered vee's). You take a 48" steel driveshaft and replace it with a carbon one, you will feel and see the difference.

 

[2112]

are you attempting to gain something by eliminating it? the actual mass given the diameter is fairly small....

Yes, I am thinking weight. My small driveline is probably 50 lbs and it is only on the one side. I have seen drag race drivelines in aluminum and CF advertized "good to 1200 horses" which is much more than I have, so I was thinking......

On the angle....my bad. I am not going to move the engine now so I will just have to replace the u-joints on a regular basis.
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[MOBILEMERCMAN]

The aluminum may work just fine but, it will need to be inspected much more often for cracks. I personally don't think it is worth the risk in a pleasure boat. I have seen an aluminum one fail. It sure does make a mess. It let go with out any warning or vibration.

I to agree a small variation in cross bearing angle is preferred. The slip spline coupler makes service easier and allows for boat movement. Any end load transferred in to the engine will cause crank failures.

 

[Sean H]

The guys who have run all 3 prefer either the steel or carbon, the alum not so much.

If built to the right spec, carbons work flawlessly. Just don't repower your boat with nearly twice the torque and leave the orginal carbons in there (ask Miccosukee).

 

[DAREDEVIL]

Yes, I am thinking weight. My small driveline is probably 50 lbs and it is only on the one side. I have seen drag race drivelines in aluminum and CF advertized "good to 1200 horses" which is much more than I have, so I was thinking......

On the angle....my bad. I am not going to move the engine now so I will just have to replace the u-joints on a regular basis.
.

Put your batt, on the other side and u be fine. 50# aint nothing in a plessure boat !!!!!
Plus if its staggered u won't feel the difrents at all !!!

 

[Chris]

The likelihood that you got the engines in perfect alighnment is pretty slim. A degree or so isn't much. You should be OK.

On the aluminum shaft, the reason they have issues is that aluminum work hardens. On something like a roadrace car, you're not going to get dramatic shock loading like you will in a boat that's loading, unloading and sometimes reverse-loading the propeller. The first thing is to have it constructed from the proper grade of aluminum. Then after welding is should be re-heat-treated. 6061 is probably the best material if you need aluminum.

On the slip yoke, you absolutely need it. There's no way you can get the spacing to a thousandth or two and the engine mounts will flex, not to mention the hull/stringer/transom.

 

[2112]

The merc input shaft assembly has a .250" back and forth ability. I assume the additional 2 inches in the driveline slip yoke is also needed?
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[Chris]

There's a fixed flange on the back of the engine and a fixed flange on the transom plate carrier.

 

[2112]

There's a fixed flange on the back of the engine and a fixed flange on the transom plate carrier.

My Engine flange is not fixed. It is part of a pinion shaft that engages the bravo coupler. That it the piece that moves .250"
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[DAREDEVIL]

My Engine flange is not fixed. It is part of a pinion shaft that engages the bravo coupler. That it the piece that moves .250"
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Got any pictures.