What is the Stock prop size for a alpha 1 out drive

[rs1lollie]

I was wondering what is the stock size prop that comes on a 1990 3.0 alpha 1 out drive?? I have a 14.25 x 19 and 14.25 x 21 , is the 14.25 the right size??

 

[rs1lollie]

Re: What is the Stock prop size for a alpha 1 out drive

Forgot to mention its a 18ft open bow maxum

 

[Rocky_Road]

Re: What is the Stock prop size for a alpha 1 out drive

No one has jumped in here...probably because there isn't any pat answer for your question. The proper prop for your engine/boat setup will be whatever pitch gives you the maximum rpm's specified for your engine...and that won't always be the same for the next guy.

As for the 14.25" aspect...if it has the clearance in your lower unit, then you are doing fine. Most dealers send the boat out the door with a 14" (or smaller) prop...but that is probably more to do with cost, and the effort to reduce torque steer for the new owner.

You should try both of your props, and decide which pitch gives you the best performance for your boating style. I use a 14.25 x 19 on my 17.5' bow rider....

Happy boating!

 

[Tubingluvr]

Re: What is the Stock prop size for a alpha 1 out drive

Without knowing a little more info there is no way to give you an exact answer.
At least your WOT and top Speed.
With that being said most 18' runabouts with a 3.0 use a 19 pitch for power prop and 21 pitch for speed prop.
You need to look at the WOT specs for your engine and run your boat with each prop at top speed to see where you are running in relation to your specs.

 

[hwsiii]

Re: What is the Stock prop size for a alpha 1 out drive

Lollie, welcome to Iboats prop forum and we will try to help you as much as we can but without more information no one can help you, and I will tell you I need more information than anyone else. But if you would like my help fill this form out and I will help you as much as I can, if you would prefer to not go to this much trouble there are other people who will help you.

Iboats Boat and Motor Info
1. Year, make and model of boat
2. Length, width and base weight of boat, look for boat decal on back of boat
2a.What is the recommended HP for your boat
3. Number of people and gallons of gas normally on boat
4. What do you use the boat for
5. Is it a Deep Vee and if so how many degrees of deadrise
6. Year, make and model of motor
7. HP and gear ratio of motor IMPORTANT
If you don?t know the ratio, you need to pull the plugs out and put a piece of tape across the prop and the lower unit and then cut it between the prop and the housing and turn the motor until the tape lines up with each other, it is easier if two people do this, so one can watch the prop while the other counts the revolutions of the motor
8. Manufacturer?s recommended Wide Open Throttle (WOT) range
9. Anti-ventilation Plate height above keel of boat if it is an outboard in inches
10. Is it a bass boat or does it have a pad bottom
11. Does it have a hydrafoil, dolefin or trim tabs
12. Make, model, diameter, pitch and whether SS or aluminum prop
13. WOT RPM and speed from your current prop and how much gas and how many people were in the boat for the test data and is the speed by GPS. If you do not have a tach you can buy a Tiny Tach for $ 50
14. Are you at sea level or a higher elevation, give us the elevation in feet
15. Has your motor been tuned up lately and have you checked that the carburetor butterfly is opening all the way, checked compression, and looked at the plugs and checked spark, all of the forgoing could be the reason your prop is not attaining full RPM
16. How long has this prop been on the boat and why, at this time, do you think it is the wrong prop
17. Does the prop show any damage that you can see
18. What problems are you trying to cure or what are you looking for the boat to do that it is not doing the way you think it should or to your expectations

REMEMBER, The numbers I give you will be NO better than the information you give me

The only thing I ask of you is to come back and give me a report of WOT RPM and speed for my database.

H

 

[rs1lollie]

Re: What is the Stock prop size for a alpha 1 out drive

1990 maxum 1800
18' length
7' 2" beam
20.1 gal gas tank
mercruser 4 cylinder 3.0 (181 c.i.d)
135hp
max rpm 4400-4800
Alpha 1 gear ratio 1.84:1
ran with 21pitch prop just me in boat and full tank of gas wot 45 mph and @ 4800 rpms. Prop was a little dinged up. also had a stingray hydrofoil on it.
Was reading a lot on Iboats about the hydrofoils, so I removed it, but have not had a chance to take the boat out and see how it runs without it.

 

[Tubingluvr]

Re: What is the Stock prop size for a alpha 1 out drive

according to the WOT specs you are right where you should be with the 21 pitch prop.