85' 25HP Mariner Prop?????

[chipster427]

Ok, I have what I think is a 1985 25HP Mariner. The only markings that I can find are on a freeze plug in the case. It reads 001185, and there are Yamaha stamps on both the case and the head. Is there any other way to determine year and model?

Now the Prop, It has a 9 7/8 x 10 1/2 on it. When I look those numbers up all it pulls is a prop for a Yamaha 30HP, and when I use something like Prop Wizard, these measurements aren't even an option for the Mariner. I'm just trying to fit a Prop with good all around performance on it. I don’t know what the current setup runs like(speed, RPMs @ WOT) because I am currently working on the boat interior and just got the motor running.

Also, I am still trying to figure out the measurements of props. I am guessing that the first number is the diameter and the second is the pitch. If that is the case, could I go with a 10 x 11, seeing how the measurements are so close? Or, Is it just going to have to be one of those things that is a Test N Tune?

Details, best I can:
14' Flat bottom Aluminum (I believe it is a MonArk)
Going back all aluminum guts, unsure of actual weight
Planning on adding Beavertail Floatation Pods
Main use is going to be duck hunting and some fishing, so there is going to be some weight to it/ in it

Suggestions please.

 

[steelespike]

Prop size is written diameter X pitch Diameter is a secondary consideration, just being sure it is intended for your motor and avoiding extremes in size.
The best way to look up a prop is by the motor model. 85 up is a 10- spline through hub prop.
When ready you should do a lightly loaded test run giving us your boat info and your wot rpm and gps speed.
Your prop selection needs to produce a wot rpm within the motors rtpm range.4500-5500.preferably near the upper limit.
Best to select a prop based on your wot rpm and gps speed.

 

[chipster427]

Thanks Steelespike, but when you say "tire based" what are you referring to? I know it's a 10 spline through hub, but i dont have a model number. The motor was stolen years ago, insurance was paid to the owner, I had a bill of sale and had the Game and Fish reinstate the motor and was able to keep it, i.e. no original ID plate. Also, is 4500-5500 RPM a standard range for 25 HP motors?

 

[steelespike]

My very limited information prior to 88, 25 Yamaha and Mariner 80-84 have a 61 mm stroke Mariner 85-89 a 60 mm stroke.
Yamaha after 88 have a 56 mm stroke.Don't know if you can measure that difference.