Prop for 1989 Alumacraft with 80 Merc

[axlr8]

Looking for opinions where I should start at with a 1989 Alumacraft Trophy 170 and a 1983 Mercury 80 Blue Stripe. Never done this before so if I am missing vital information, just ask and I will get back to you.

Looking to get a ballpark area on what prop to use, boat is going to be used for Walleye fishing in northern MN. I dont neccessarily want top speed, I'd rather have good lower end to get up on plane and any top end is just a bonus.

Thanks for any advice that can be offered.

 

[axlr8]

Off of what the Mercury Prop selector, they are saying that I should be around the 12.75" Diameter, 21 P 3 blade prop. Mercury part number 77348A45.

I had to use a 2000 75 classic as my motor due to site limitations.

 

[anzomcik]

I do not know gear ratio but shooting from hip with not looking at anything for reference i say 21 pitch is high, my guess is 15-17 pitch

 

[axlr8]

Is there a way to figure out gear ratio? From looking at the motor? Serial number: 623534

 

[Scott Danforth]

There is a sticky with the info required for prop questions

 

[axlr8]

There is a sticky with the info required for prop questions

Here is what I have from that:

1: not applicable
2: did not come on the boat, or with prop
3: see above
4: not applicable
5: 1983 Mercury 80 4 cylinder 2 stroke.
6: 1989 Alumacraft Trophy 170 (weight unknown due to current rebuild.)

 

[Scott Danforth]

1 and 4 are vary applicable and what is required to pick a prop. 5 and 6 are optional

So once you post your WOT rpm, we can pick a prop

 

[axlr8]

1 and 4 are vary applicable and what is required to pick a prop. 5 and 6 are optional

So once you post your WOT rpm, we can pick a prop

How do I do this? I have never ran the motor/boat together. Should I pick an ideal RPM that other people have run them at? Or am I stuck with having to buy a prop that is "close" and give my results then?

"1) Performance issue you are trying to correct.
2) Current prop manufacturer, model, aluminum or stainless as a minimum.
3) Current prop diameter and pitch (required).
4) Wide open throttle RPM and speed with an average load (very helpful)
5) Engine/drive make, model, year, and HP
6) Boat make model, year, length and weight"

I guess what I am looking for is an 'ideal prop' to start with. And then I am going to be able to get back with more detail of what I am looking to change/fix.

As far as now, its been reccommended that I try a 15-17 pitch prop. I just need something somewhat close to start with and go from there. Im looking at some Michigan Wheel props at the moment.

 

[Sea Rider]

See if you can borrow props at a prop shop to try them out, that would be a low investment deal. If boating heavy loaded start with a 15 pitch of your brand preference and report achieved wot rpm on a test run on flat calm no wind water cond.

Happy Boating

 

[axlr8]

I called a few local prop shops and they do not offer the prop borrowing like you suggested Sea Rider, but they were able to suggest that for the boat that I am putting the motor on, I should be in the 15-17 range depending on the weight of the load. I do have both a 15 and 17 prop that I picked up used and damaged, and I will be getting those repaired and using them to test on the boat. Thanks for all of the help, I will be back in a while to update my status and what I found worked best for the boat.