which gear ratio?

[DirtyE]

O.K. I'm getting some mixed info on which is the best gear ratio for my boat, 26 billfisher with ad41, I have A4 props, I would like to be able to cruise at 20kts, so lets hear it from some blackman experts. Thanks Erik. 1.95 or 1.78?

[Knot Now]

I have a 97 Billfisher with 41P with 1.78 gears. I run tweeked A3s and she will cruise at 20 kts when she has a clean bottom and half a load of fuel at 3000 RPM to 3300 depending on the seas.

I have been told that the 41P has a little more power than the 41A.

[DirtyE]

Are the 1.78 suppose to be stronger than the 1.95, someone mentioned that in another post. I will need a new outdrive so trying to figure which way to go. Erik

[Knot Now]

I have read that also.
It is used with the higher HP engines ... i.e. 230 HP

[NoSlack]

Volvo offer 3 different gear ratios for our vintage DP drives. 2.30-1, 1.95-1 and 1.78-1

The idea is to match the right gear ratio to your horse power so you can stay in the middle of the prop range i.e A0 through A10. Ideally you want to be running A5s, be able to hit max RPM fully loaded and not have the engine temp rise above the manufactures guild lines.

Most diesels with less than 150 HP run the 2.30-1 gears, 150 to 220 HP run the 1.95-1 and the higher HP engines can push the 1.78-1 gears. A step change in gear usually equates to a 2 pitch change in prop to get the same results. 1.95 gears ans A4 props will be very close to 1.78 gears and A2 prop for the same HP engine without compromising max RPM or engine temp.

Staying with the 1.95 gears and testing out the next higher pitch prop is a lot cheaper than changing gears and starting over on finding the right pitch prop for the boat. Over the years most of the 26' with the AD41 have run the 1.95 with A3, A4 or A5 props. No reason to go away from what's been working for the fleet for so long.

Mike

[DOGHOUSE26]

Mike you hit it right on the head with the best explanation I've ever heard or read.

[DirtyE]

Well i believe we are going to stay with the 1.95, but volvo has the complete OD on back order, so we would have to put on a lower and go through the upper, 1.78 complete is available, it would be nice to get a all new OD, but I feel the 1.95 is probably the correct combo. Well with every answer a new question arises, I geuss I'm getting a real crash course in this boating thing. Thanks guys, Erik

[Honeygirl]

What’s wrong with Zack's Outdrive it's a 1.95 and he's making you a smoking deal on it. You could just use the lower and sale the upper and save your self a lot of cash. I know the drive was used less than a year before he re-powered. Zack is religious about changing his fluids every hundred hours.

[DirtyE]

theres nothing wrong with zacks he may still be a option, but its in insurances hands and its at the repair shop now getting a qoute, so I goota wait to hear from, state farm, Zack I will call you back when I get more info. Erik