10M Express what is the best prop?

[Trojan10m]

Attached pictures. With measurements hopefully this helps.

[prowlersfish]

I wonder if RWS has photos of his boat's undersides?

[RWS]

these photos are from 2005, BEFORE the refit to diesel.

I have the original factory order paperwork on this boat, and can confirm she came from Lancaster with big block 454 Crusaders.

I sent these struts back to John for resale, after the refit was completed, as I ended up going to 1.75" shafts with one strut per side

I was told the reason 2 struts were required was due to the torque "twist" on the shaft, due to it's length/width.

If that boat was mine, I'd look into putting Aquamet 22's on her

Might be best to discuss this with John Leed first to see what his thoughts might be.

RWS

Photo taken before diesel refit.

DSC00010.JPG (75.9 KiB) Viewed 13111 times

[prowlersfish]

Interesting, the extra strut and the V-strut. I wonder if Trojan did that because of the big block or a change after the first year or 2?


One thought on the shafts is you have no more torque on them than when the boat had small blocks due to it having the 1.5 to on gear vs 2.0 . But you would be spinning them faster.

Do you know your shaft size offhand? Just wondering if that was changed?

[RWS]

Interesting, the extra strut and the V-strut. I wonder if Trojan did that because of the big block or a change after the first year or 2?

The photo is of a 1983 (actually a 1982 hull) with 2 struts per shaft (factory struts were 1.25")


One thought on the shafts is you have no more torque on them than when the boat had small blocks due to it having the 1.5 to on gear vs 2.0 . But you would be spinning them faster.

Do you know your shaft size offhand? Just wondering if that was changed?

[prowlersfish]

The early 10 meters did come with the I strut, so that is a stock set up.

[Trojan10m]

Ii finally got time to test the boat’s RPM at the dock and also under load. Just in case there was change under load.

Here is the breakdown of RPM indicated verse actual with speeds.

indicated- actual - MPH
2500 - 3000 -12 ish
3000 - 4000 - 16 That is where the 4 barrels open mechanically
3900 - 4800 to 5000 - 21

Props are 3 blade 16 x 16 cupped. Clean bottom. Fuel load of fuel. 3 people aboard.

Let me know what you all think. Thank you.

[RWS]

if you were to compare your numbers to the chart I posted on page two, one might conclude you are significantly underpropped = less than efficient

Likely a result of a gross error by a P.O.

RWS

[prowlersfish]

Ii finally got time to test the boat’s RPM at the dock and also under load. Just in case there was change under load.

Here is the breakdown of RPM indicated verse actual with speeds.

indicated- actual - MPH
2500 - 3000 -12 ish
3000 - 4000 - 16 That is where the 4 barrels open mechanically
3900 - 4800 to 5000 - 21

Props are 3 blade 16 x 16 cupped. Clean bottom. Fuel load of fuel. 3 people aboard.

Let me know what you all think. Thank you.

Interesting If the Actual rpm is correct then you are a little under propped going by rpm. Is that both engines at wide open ? Photo tach at all RPMs ? ( not calculated) . Going up to 16x17 cupped Would get you closer to rated RPM (44-4500 ?? )

Going back to 2.0 gears and bigger props could yield better numbers, But I question doing this because of the I strut and no extra cutlass. With the extra torque of the 2.0 that could be an issue, Trojan changed it for a reason.

[RWS]

This situation is an unusual circumstance.

FACT: This boat was originally equipped with small blocks.

FACT: Everything from the gears back is not compatible/efficient to be run with the 454's horsepower or torque.

suggest the following items be reviewed by John Leed:

1. put the correct 4 blade props in for maximum efficiency and power

2. put the correct gear in (should be cheap and plentiful) to obtain the correct gear ratio to match the prop

3. replace the shafts with Aquamet 22's to eliminate the shaft twist/strut issue. (just my own idea)

Again, these three items need to be evaluated by Mr. Leed as he will have the best possible advice on this matter.

Simply changing the props may or may not create a dangerous situation as those big blocks put out substantially more torque than what she was originally equipped.

Consider this a safety issue.

Imagine the strain on those shafts as she climbs up on plane.....

Imagine a shaft torqued in half, then exiting out of the back of the boat - you now have an open shaft log with no shaft.....

Don't know how likely this may be, I'm not an engineer.

I'm simply pointing out the worst possible scenario.

This truly is a question for Leed.

BEST !

RWS

[prowlersfish]

Trojan did use that shaft set up with big blocks ( fact )
With the present, 1.5 gear torque on the shafts is reduced to about what the were with the small blocks and 2.0 so not an issue IMO if you stay with 1.5


You can Try and repitch what you have (add a inch) or go with 4 blades

Or can replace gears and bigger props and do shaft work . Trojan did change the shaft / stut set up for a reason early on so I would expect issues going to 2.0 gears without redoing the struts , Going to Aquamet 22' shafts would not be a bad idea.

How much do you want to spend $$$$

[my10meter]

My 10m Express has 454s and 192..1 trains. Replaced with 4 blade props. 3150 cruise 23.7mph under heavy load. 23.7 is the sweet spot for efficiency. Data collected from 9000 hrs of use

[Trojan10m]

Changing gears, shafts, and running gear probably won’t happen for a couple years. So what options for props am I looking for 3 blade 17x17 or what 4 blade options. Does anyone know how big will fit under the boat. Thank you.

[prowlersfish]

They put 18" props on the express. But the problem is with your 1.5 your limited on how much wheel you can turn. If you with an 18" diameter you would have to go way down on the pitch. even more so with 4 blades.

[RWS]

The best way to do this is to run the numbers on your current props

RPM - KTS

for every 100 RPM

do this in 2 directions to allow for tides

do this with full water

and full fuel

Have a reputable prop shop measure the existing props and interpret the EXISTING data

with this factual data they can either modify what you have, or recommend what would work

RWS