Repowering and Repropping

[sea_ya]

Below is a message that I posted on the Donzi forum, but have gotten no responses. Anybody here have any experience or suggestions?
Thanks,
Hello - I don't have a Donzi, maybe in the future, but I have inherited a 1988 20' bowrider from my father-in-law, that was powered with an AQ231B and a Volvo Penta 285 outdrive which is very similar to some early Donzis.
Engine block was freeze cracked big time, so repowering was in order. The solution turned out to be a 350 4bolt main block which grew to a 383, and a complete outdrive and cone clutch rebuild. The engine idles and runs and pulls smooth and after several different props(see below) the outdrive has proven to shift well, does not slip and doesn't leak. On to finding the correct prop.

Original 305 SBC, ran 49-51 MPH, with V-P alum props 15x19/5200rpm or 14x21/4700 rpm.

I knew that repropping would be required, so I started to collect props that fit this V-P long hub 285(1.61) outdrive.
1. V-P SS Ultra, 14x22RH
2. V-P SS Ultra, 14x24RH
3. V-P SS Ultra, 14x26RH
4. Hill SS 15x25LH
5. S&S LH Cleaver

Started with the the Ultra props, #1 and #2 above both had slipped hubs. What would you expect from ebay right?
Checked #3 above which had punch marks and had slipped also, 14x26, had it rehubbed and reconditioned by a shop that was highly recomended. It slipped with the rehub. I'm a little upset about this one. Are these props inherently difficult to rehub?

?? At lower RPMs 3000-4500, the 14x26 didn't slip but it caused the boat to pull hard to the left. Is this a characteristic of the these V-P Ultra props due to rake or some other characteristic? Never did get the outdrive torque trim tab adjusted to neutral, since at WOT the hub started to slip.

Next I installed the LH Hill SS prop, that I think is called the thrasher prop, but its difficult to be sure. This prop was NIB and ran great, no vibration, after adjusting the outdrive trim tab and achieved very neutral handling with this prop at any rpm. Ran WOT 5400rpm/58mph with this prop.

As I understand the cleaver prop needs to run partly out of the water, so i don't think I'll have much use for it.

I've read some posts on this forum about a Solas SS prop being recomended for the V-P outdrive but i'm not sure which model solas and there was talk that a 23 pitch size might be comparable to a 25 or 26 inch prop of other manufacturers.

??Any thoughts or recomendations on the adventure described above?

??Anybody need any SS Ultra props that require a rehub or a cleaver prop with a slight repairable ding(shipping damage)?

Thanks,

 

[RicardoMarine]

...................................

................
Hello - I don't have a Donzi, maybe in the future, but I have inherited a 1988 20' bowrider from my father-in-law, that was powered with an AQ231B and a Volvo Penta 285 outdrive which is very similar to some early Donzis.
Early Donzi (70s vintage) would have been equipped with a 250 or 270 drive. The 285 was later, and was specific to the V-8 engines.

Engine block was freeze cracked big time, so repowering was in order. The solution turned out to be a 350 4bolt main block which grew to a 383,
Hopefully you steered clear of these for a 6.3L marine build:

Also, very carefully watch your Progressive and Total advance, making sure that it is within specs.
This is extremely important for a Marine gasser...... especially for a 6.3L build.

and a complete outdrive and cone clutch rebuild. The engine idles and runs and pulls smooth and after several different props(see below) the outdrive has proven to shift well, does not slip and doesn't leak. On to finding the correct prop.

Original 305 SBC, ran 49-51 MPH, with V-P alum props 15x19/5200rpm or 14x21/4700 rpm.

I knew that repropping would be required, so I started to collect props that fit this V-P long hub 285(1.61) outdrive.
Technically....... there is no long hub/short hub outdrive shaft......... only long/short hub propellers that each require the correct spacer/line cutter length. 1. V-P SS Ultra, 14x22RH
2. V-P SS Ultra, 14x24RH
3. V-P SS Ultra, 14x26RH
4. Hill SS 15x25LH
5. S&S LH Cleaver

NOTE:
a..... when running a RH prop, you will be driving from the transmission's upper driven gear.
b..... when running a LH prop, you will be driving from the transmission's lower driven gear.
with scenario "b" make sure that the shop who did the transmission work also replaced the brass split ring keeper!

Started with the the Ultra props, #1 and #2 above both had slipped hubs. What would you expect from ebay right?
Checked #3 above which had punch marks and had slipped also, 14x26, had it rehubbed and reconditioned by a shop that was highly recomended. It slipped with the rehub. I'm a little upset about this one. Are these props inherently difficult to rehub?

?? At lower RPM 3000-4500, the 14x26 didn't slip but it caused the boat to pull hard to the left. Is this a characteristic of the these V-P Ultra props due to rake or some other characteristic? Never did get the outdrive torque trim tab adjusted to neutral, since at WOT the hub started to slip.
You will want to adjust the "torque tab/trim fin" as to help counter steer torque.

Next I installed the LH Hill SS prop, that I think is called the thrasher prop, but its difficult to be sure. This prop was NIB and ran great, no vibration, after adjusting the outdrive trim tab and achieved very neutral handling with this prop at any rpm. Ran WOT 5400rpm/58mph with this prop.

As I understand the cleaver prop needs to run partly out of the water, so i don't think I'll have much use for it.

I've read some posts on this forum about a Solas SS prop being recomended for the V-P outdrive but i'm not sure which model solas and there was talk that a 23 pitch size might be comparable to a 25 or 26 inch prop of other manufacturers.

??Any thoughts or recomendations on the adventure described above?
Selecting a propeller often involves lots of testing and trying of different props.

 

[sandkicker]

Classically, one picks a prop so that it runs, when at WOT, within the designed/specified maximum WOT engine RPM range for that engine. There are no "general rules". For example, my MERCRUISER factory crate 260HP 5.7L MIE (2bbl) has a MAX WOT RPM range specified on the decal on the flame arrestor that does not agree with any published spec I've ever been able to get from MERCRUISER for that engine model. Bad things happen to engines that do not get to the minimum RPM's specified, or are run at above the maximum specified RPMs. IMHO, when you "roll your own" engine, your are "on your own" with determining correct engine RPM range and by extension, the optimal prop. I've not propped all that many different engines, but my experience is that usually for any given boat/engine use condition, there is only one prop size that really "works" well... and at least for VOLVOs, only one drive ratio that will work for a given engine technology, i.e., number of cylinders (1.61 for V8s).

 

[sea_ya]

I looked at several marine quality crate or replacement 383 SBC's but didn't like something about every one, so I built my own. I used race quality forged pistons, with 2 valve reliefs.

What's the deal with the GM F/D pistons that you refer to?

I am very familiar with marine engine loading and high speed spark knock. Fortunately on my boat, you can hear it, if you know what to listen for, through the fiberglass engine cover when it has occurred in the past when performing timing experiments.

My local V-P dealer has some very experienced people when it comes to rebuilding the cone clutches and knows all the best practices and upgrades that can be applied to it. The initial "slipping" that I experienced was all prop related, the outdrive is rock solid.

Again, any comments on the props would be appreciated.

Gilbert.

 

[RicardoMarine]

.........................

I looked at several marine quality crate or replacement 383 SBC's but didn't like something about every one, so I built my own. I used race quality forged pistons, with 2 valve reliefs.

What's the deal with the GM F/D pistons that you refer to?
GM F/D = Full Dished.
The SBC Marine Engine (especially the 6.3L build .... aka 383) needs a "quench effect" built into the combustion chamber.
This requires a rather special piston profile, and a specific quench dimension.


I am very familiar with marine engine loading and high speed spark knock.
Not spark knock........ we are wanting to avoid "Maine load Detonation"! Fortunately on my boat, you can hear it, if you know what to listen for,
Detonation and Pre-Ignition are not the same phenomena. Pre-ignition is typically audible...... whereas Detonation is not always audible.

through the fiberglass engine cover when it has occurred in the past when performing timing experiments.
YIKES! I would never recommend experimenting with Marine Engine Ignition Advance. Maybe while on a Dyno..... but not in the boat!

We need spark advance in order to achieve a good LPCP at each RPM......... but certainly not Too Early.
Too early, and we may create very destructive Detonation.


My local V-P dealer has some very experienced people when it comes to rebuilding the cone clutches and knows all the best practices and upgrades that can be applied to it. The initial "slipping" that I experienced was all prop related, the outdrive is rock solid.

Again, any comments on the props would be appreciated.

Gilbert.