Willard 7m seaforse repower.

[skidoodog]

Follow up to prop testing.

Thanks all for chiming in. My props on hand for testing are limited for now.
I switched back to the original fall test prop. 17.5 x 21 inch aluminum.
Torque roll. Is 50% of what it was. It's safe now at least. Dangerous
With the 17.5 x 21 cupped stainless.
Lost almost a knot at the top end. Who cares when the boat stops trying to kill you.

Tried a 17 x 23 cupped stainless. Gained back my top speed and reduced roll . Got a gut feeling that he boat was just not happy with that prop. I have data that shows not much advantage to this prop.

I have sent both stainless props out to have the cup removed. Also the good aluminum prop in for a balance and tune up. I will start over next week.

Cheers

Cheers

[skidoodog]

Got the aluminum prop back from the propeller tuner. It was square and true and had not bent under load. It Needed nothing on the balancer. It was right all along and seemed to be the best handling prop for my application. However.

I have been doing more research on my torque problem as I wait for my stainless props to be tweaked. It seems physics and the laws of action and reaction can not be denied.

My imperfect solution with the aluminum prop was really only a stop gap solution from the information I have gleaned. I would have run in a very short time into the reality of breaking my Mercury aluminum prop....and not in the nice traditional way of smashing it on a rock but by shearing the blades off from too much flexing and load. Blades departing under load could lead to a massive over rev condition. That could be very expensive on a Volvo D6 and dangerous if it happened at the wrong time. Not a risk I am willing to take.

I have ordered a Konrad 560 counter rotating drive lower. I call an end to my single prop experiment. The 560 will bolt right up to the 520 drive and my torque roll should almost disappear. As an aside Konrad tech support says the fastest 520 drive application they have ever heard of is 43 knots so my 40.8 is not far off. The 520 is a medium to slow speed drive. It's made for best performance at 25 knots on a heavy boat.


The 560 drive lower is on its way.

Stand by for further.

Cheers,

Dave

[ncp]

Keep us posted. I totally understand keeping the diesel. My Willard was the most seaworthy boat I've even had.

[Bigtalljv]

And you didn’t buy that boat to be the fastest thing in the ocean. It’ll go anywhere anytime.

Although 40kts is still really moving. I got a 250 outboard on mine and it would do 50 before the t-top, but cruising on the ocean here is high 20s. I’m sure it could go faster it just starts to not be fun.

[jwalker]

Hehe...You were in denial, you knew you had to do it! If the duo props, front and rear, are well matched you should have no torque reaction. Now, about those trim tabs.....

[skidoodog]

Look what just arrived...its getting real now. Hope to have it installed in a few days. 2 sets of used props for testing purposes.

Its very shinny

[jwalker]

[skidoodog]

The 560 lower is now on. How long would you guess it takes to swap the drive...

Well it took a lot longer than you would expect and willard owners take note. The drive lower and upper were all but fused together. I was somewhat pressed for time so a few days soaking in penetrating oil was not an option. After a few hours of beating and prying on the drive we strapped the drive down to the extended legs of a sea contained converted to ship liquid fuel. It was very heavy. We then lifted with the hydraulic cylinders while the fork lift was used to hold the front of the trailer down. It worked but unfortunately I broke part of the cavitation plate off at the back of the drive. It gave us just a crack to start in with the screw drivers and shallow ramp wedges.
If I did it again I would try to remove the studs from the upper portion of the drive and most of all not be in a hurry. This drive is just a spare for me now. I hope I never need it.

Konrad sent me 2 prop sets. 25/26 inch set and 22/23. We had concluded that 23/24 was probably right but they did not have stock so I took what I could get for a trial.

I mounted the 25/26 set.

Konrad also recommends a 10 hour break in period on the drive with the first five hours limited to 75% of max and a half dozen other instructions. Basically, go slow, be gentle and don't over load the drive. I have 4 hours on now of slow poking around at varying low power settings. After 5 hours brief full power runs are allowed.

I did have the occasional little burst toward the end of the day. In summary this is what I have found so far.

The boat now backs up straight and is very controllable in reverse. Unlike before. The boat now tracks straight at low power settings and while planing. No hunting back and forth and holds a very straight track planing.
The boat is grippy in turns and I was unable to provoke any cavitation or aeration in the turns.
The boat is now responsive to drive trim. I have never had a boat that was so unresponsive to trim than this willard with the 520. Mostly I left it trimmed fully down and that was it. Trimming made almost no difference until trimmed way up and the handling got squirrely It was strange.
Now with the 560, it trims like any other sport boat. Bow comes up, sweet spot is found with trim and the boat is happy. You can feel the boat accelerate once in the slot and it sits right on the water. Straight, no crab, no torque effects. The drive is smaller and shorter, you can feel less drag in the seat of your pants.

Just as the new engine transformed the boat, this new drive also has made a huge difference for the better. I wonder how this drive would have worked with the original Cummins....the difference is that big.

All that said, this was the wrong prop set. I could have guessed. It was way over propped and the fuel flow generally way too high as compared to the 2.5 Volvo propeller curve for this IPS 600 engine. The supper charger stayed on continuously between 1200 and 2000 rpm. Very loud and irritating.

Test conditions: We have had an early heat wave here in southern Ontario. Temp 28, 82f, water temp 18, 64f sw wind at 15kts and just a little light chop. Perfect conditions.

Some numbers just for fun.

rpm, speed in knots, fuel flow liters(finer measure than rounded of gal)

1000 7.7 8.8
1500 17.7 24 (supper charger on)
2000 31 36 (supper charger on)
2300 36 39 very briefly due to break in procedure, no s.c.

I have installed the 22/23 prop set and hope to test again in the next couple of days. This is great fun now and I am very pleased.

Cheers, DA

[skidoodog]

https://youtu.be/ovaCdFT7DvY

[jwalker]

Very cool! I've been waiting for an update.

I'm pleased you're pleased and it's good you're now beginning to properly enjoy the boat. Duoprops are remarkable and I've no idea why they aren't more popular. I wonder how many folk just put up with a single prop drive in the belief that it's just how a boat is.

I hope you put a good smattering of waterproof grease on the flange and fittings when you reassembled it.


Now, about those trim tabs....