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280 power trim outdrive

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scorpion

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i am new here so hi to everybody.i have a 83 cris craft scorpion 350 chevy with a powertrim 280.it has the 2 bolt helmet.my question is will a 280 1 bolt leg bolt right on.my trans sounds a little noisy when i have it running with the muffs on.i picked up a 280 leg that has the single bolt and was rebuilt last season so i want to make the swap thanks for any input
 
You'll need to change out the clamp ring if you intend on useing the one you picked up or the steering helmet for the one bolt style.
Running on the muffs creates lots of weird sounds we don't hear in the water, the main noise I hear about all the time is, sounds like marbles in there and this is normally the SS exhaust shutters in the bottom hose clanging against each other at idle. You might check this.
 
Gary is referring to the "bearing box" clamping collar. This will be the forward-most aluminum portion of the transmission! The part that the drive bellows clamps onto!
This requires special shimming if you were to do this, and if the four bolts are corroded, some special techniques!
I'd suggest NOT risking this, unless you have prior experience!
It will be easier for you to change the helmet to the single pin helmet!

Which ever you choose, it would behoove you to install a new shift mechanism seal. These are prone to going bad after X amount of usage.
If Black or Brown in color, it is an old one!


Keep in mind that if you swap transmissions or lower units ONLY, there is critical shimming that mus be performed. No Exceptions!

Your 280 replacement must also be of the correct over-all gear ratio.
For your engine, this will be the 1.61:1.
The lower unit ratio will be stamped into the bearing carrier just ahead of the prop shaft "ring anode"!
Transmissions in this series are all the same ratio!

Good luck. :)
 
are the helmets all the same for the aq series drives.i do have another drive that has no lower unit.it has the 2 bolt trans. on it. is it a huge job to set up the shims.is it something that a car guy could do or do you need special equipment thanks
 
scorpion said:
are the helmets all the same for the aq series drives. i do have another drive that has no lower unit. it has the 2 bolt trans. on it. is it a huge job to set up the shims. is it something that a car guy could do or do you need special equipment thanks
Click to expand...

With the early drives, yes, the helmets are interchangeable with the collar steering forks. Once past the 290 or so...., they are not same!

Volvo gives us codes to be used for calculating the shimming.
However, on these older drives (that may now have been re-shimmed during bearing replacement), I suggest NOT using the codes.

For a transmission swap, I suggest "Over-Shimming" the underside of the transmission.
With the transmission lightly clamped into position (O-rings removed/surfaces very clean) you take many readings between the two cases. Come to terms with a reading that is ambient!

You do the math, and reduce the shim pack by a value that gives you a .003" to .004" squeeze on the lower driven gear bearing when fully installed and tightened in place!
Ideally, the two cases come to within ZERO when the shimming is correct!
What we are doing, is "Squeezing/Clamping" the lower driven gear bearing as to prevent it from spinning within the cavity.... yet closing the "Gap" between the two cases!
It is a very simple and accurate procedure...... actually, moreso than using the codes, IMO.


The lower unit shimming is NOT the SAME!
This Pre-load is a Negative pre-load!
 
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