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280 Drive swap question

B

boatgator

New member
Hi,

I have a 1979 21' Fiberform walk around with an AQ280DP serial number 2872891B. I want to buy a spare drive and have the existing DP serviced as I am getting water in the oil. I use the boat for work daily and can't afford to have it out of service. Can I take any 280 I can get my hands on and install it on my boat only for below 7 knot service while the DP is getting serviced? What is the significance of the ratio for low speed service?

Thanks in advance for your knowledge.

B
 
Last edited:
boatgator said:
Hi,

I have a 1979 21' Fiberform walk around with an AQ280DP serial number 2872891B. I want to buy a spare drive and have the existing DP serviced as I am getting water in the oil. I use the boat for work daily and can't afford to have it out of service. Can I take any 280 I can get my hands on and install it on my boat only for below 7 knot service while the DP is getting serviced? What is the significance of the ratio for low speed service?

Thanks in advance for your knowledge.

B
Click to expand...

i would first (before pulling anything apart) perform a pressure/vacuum leak down test to determine where the leak is. Oil must be drained for the pressure test.

The final reduction occurs in the lower unit. Without knowing which Engine, I cannot suggest a lower unit ratio!

4 cylinder = 2.15:1 in a s/p
6 cylinder = 1.89:1 in a s/p
v-8 = 1.61:1 in a s/p
(s/p = single prop)


when swapping any transmission or lower unit (using the current Intermediate housing), critical shimming calculations
must be made.
In other words, we cannot just simply remove one unit and install another without doing this!


My advice;
make darn certain that the person doing the re-seal has AQ series experience, and that this person has the proper bearing carrier puller tool.
This person should also know how to remove the eccentric piston for the seal replacement, and that the new seal is directional.

when a re-seal alone is done correctly, no changes to any shim values need to be made!
But again, if you are temporarily replacing components (transmission or lower unit), the shimming process must be observed.

My advice #2;
....get all parts and tools lined up...... new seals, new O-rings, correct gear oil, etc!
.....do the leak down test.
.....tear apart what you now have and re-seal.

Baring no trouble, this can easily be done in one day!


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Last edited:
Thanks, the DP is on a 40D 6 cylinder 160 hp. I will hunt for a 1.89:1.

B



RicardoMarine said:
i would first (before pulling anything apart) perform a pressure/vacuum leak down test to determine where the leak is. Oil must be drained for the pressure test.

The final reduction occurs in the lower unit. Without knowing which Engine, I cannot suggest a lower unit ratio!
4 cylinder = 2.15:1 in a s/p
6 cylinder = 1.89:1 in a s/p
v-8 = 1.61:1 in a s/p

when swapping any transmission or lower unit, critical shimming calculalation
Click to expand...
 
Ok........ although for temporary use that may work, you will want the 1.61:1 for that Diesel engine.

By the way....... you caught me doing an edit to my first post.
Please read it again!


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