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AQ231B-285 Prop Exercise

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sea_ya

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I replaced an expired 305 with a rebuilt 350 and am in the process of getting the right prop installed. The boat is a 21 foot sport boat. While the engine work was in process, I purchased 3 VP Ultra SS props off ebay, 14x22, 14x24 and 14x26. I also aquired a RHM Intl, 15x25 Ron Hill Signature series SS prop. Also had the upper gear case and cone clutch rebuilt. Everything is sorted and working except the prop. The VP props have all "spun" the center hub, the RHM prop holds the motor at WOT, but RPMs a little too much, 5400 rpm. The VP Ultra props are supposed to be performance props, and the RHM prop doesn't look as ***y but right now it works. Does anyone know anything about the RHM props? Is it worth it to get the VP 14x26 rehubbed? Who makes performance props for the AQ series of drives?

Thanks,

Sea_ya
 
If you are able to run 22", 24" and in particular a 26" pitch prop and reach a WOT of 5.4K rpm, your boat is most likely small, light weight, and is over-powered in terms of a conventional type boat.

The AQ series lower unit may not offer the correct gear reduction for this boat. The tallest AQ series V-8 ratio is 1.61:1!

If you could even find one these days, you may want to try a 280E drive lower unit.
http://www.marinepart-s-e-x-press.com/vp_engine_finder.htm << Put this into your browser and remove the 3 hyphens

These offer a 1.45:1 over-all reduction.


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mmmm.... I'd get the 24 pitch prop rehubbed first. If it's not correct, it will may still be close enough to use as an emergency/spare for the correct one, i.e., next size up or down.
 
Let's re-think this.

The boat is a 21 foot sport boat....... correct?
It's not a super G0-Fast style light weight hull........ correct?
Engine is a Marine built GM SBC 5.7L .......................... correct?

The stern drive is an AQ series Volvo Penta s/p (single prop) .......... correct?

You are able to run a prop pitch of approx 26", yet your WOT RPM is still TOO HIGH.......... correct?

Have you considered that your lower unit may NOT be a 1.61:1 ?????????
It may be a 1.89:1 !!!!!!!


Kim said:
IDK will a duo-prop lower fit the 285?
Click to expand...

The 285 is basically a 280 but in the 1.61:1 V-8 engine reduction only.
Yes........ a Duo Prop lower unit can be adapted to this drive.



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The drive is definetely an AQ285 with the 1.61 ratio.

It is not a lightweight racing hull.

The engine started life as a marine SBC 350, but it was just as easy to build a 383, so that's what it it is. The carb is a marine holley from an AQ271 and it has an aftermarket marine cam from a company that knew exactly what I was doing. I wanted information about props and didn't want to debate engines. I don't want to put a big cruiser prop on it just to get the RPMs down. I'm the only one who pilots this boat, so it won't see extended time at WOT.

Sorry for the mis-information.

Thanks for any further information or thoughts on prop suggestions.
 
An aluminum prop will bring the Rs down some with the same size and pitch as SS. If your not concerned with speed, for best economy find the RPM at full spark advance and just run it there. Normally around 3/4 throttle
 
You do need to monitor the plugs if your under propped you risk burning valves and pistons. The only thing that cools the valves/pistons is fuel. If the plugs come out powdery white your running too lean. You want a nice toasty brown on the electrode insulators.
 
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sea_ya said:
The drive is definetely an AQ285 with the 1.61 ratio.
Did you verify this by doing a turn count...... or by the bearing carrier stamped numbers?

FYI...... technically speaking, the AQ (followed by 3 digits) would be an Engine designation, whereas the drive itself would be a Volvo Penta 285 drive.


The engine started life as a marine SBC 350, but it was just as easy to build a 383, so that's what it it is.
Hopefully a 383 without the GM F/D pistons.

The carb is a marine holley from an AQ271 and it has an aftermarket marine cam from a company that knew exactly what I was doing. I wanted information about props and didn't want to debate engines. I don't want to put a big cruiser prop on it just to get the RPMs down. I'm the only one who pilots this boat, so it won't see extended time at WOT.
This is great!
WOT RPM is a test RPM ONLY...... and should NEVER be sustained for any duration.
Since you are the only person who will operate this boat, you should be OK being "under-propped"!
Being "Over-Propped" is what may cause Engine damage, and at any RPM!!!!!!
Click to expand...
 
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