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Replacing AQ271

T

tedm2

Contributing Member
I am upgrading to a new engine and am considering going to an EFI unit instead of carbureted. The salesman says I should go with a carb engine since it has less horsepower and the AQ series outdrives (280,290, SP and DP) are not built to handle an engine rated at 320hp.
I would like to go with the EFI for the fuel savings and extra power (the price is only $500 more) but I do not want the outdrive to fall apart.
Your thoughts would be appreciated.
 
For how long are you going to run at WOT so that the output is 320HP? If only occasionally, and as I suspect you will limit it to aboout 80%-85% of the load, that should not be a concern. You probably know that there is a package (AQ311A-AQ311B) which is rated for 307HP and comes packaged with an SP drive. In my books, the 13 HP difference between this package and the one you talk about should not make a difference in the drive longevity.

If I was in your shoes, I would install the EFI engine (that is, if that is what you want) and just limit the load at which I would run it.
 
25 years ago our shop took care of two offshore race boats that had over 600 hp BBC in front of the AQ 280 SP and they never had a problem but we did change a few misc parts in the upper gear to make sure they had a better chance of survival. Couple minor adjustments in the lower as I remember also.
 
el_pescador said:
For how long are you going to run at WOT so that the output is 320HP? If only occasionally, and as I suspect you will limit it to aboout 80%-85% of the load, that should not be a concern. You probably know that there is a package (AQ311A-AQ311B) which is rated for 307HP and comes packaged with an SP drive. In my books, the 13 HP difference between this package and the one you talk about should not make a difference in the drive longevity.

If I was in your shoes, I would install the EFI engine (that is, if that is what you want) and just limit the load at which I would run it.
Click to expand...
Yes... key point!

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Your AQ271 will use the 290 transmission.... maybe the SP ... not sure without looking it up.......... but one of which is not all that different from a 280 as for strength. No worries that I can see if all is good within the unit! (bearings/gears/clearances/etc)
I put 280 HP against twin 250 drives for years... no issues!

Also, perhaps your salesman is not aware of the RPM at which the horse power rating is taken for some of the newer engines. It's no longer like in the days of the AQ 260 or M/C 260!
GM now likes to tweak these numbers a little bit by rating the engine at an RPM where we certainly do not operate them!
Can you imagine trying to see if you can achieve 5,400 RPM while out cruising? :eek:
BTW....... WOT rpm should NEVER be thought of as a Sustainable RPM.

I think you will be fine, but read this.
FYI.... I'd highly recommend that you look at the two main drive gear bearings.... replace if need be.
I'm seeing more and more of these that are questionable.... and if questionable, they get replaced! No ifs ands or buts!

These are very critical when a drive like this ages, and behind V-8 horse power in particular!
So if you were to start fresh here with your new engine, it's a plus for you.

.
 
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Many people have gone the extra mile (either willingly or unwillingly) to attempt to destroy VP drives. Just a few have succeeded.:D:cool:
 
Ted, FYI....., I'm pretty sure that your flywheel cover will only accept the smaller 153 tooth flywheel. So make sure that the old one can be re-used, or that the new engine comes with the correct flywheel.
 
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