XR4 Blackmax 150 - can't find a prop to fit

[mack4k]

Hello all - I believe i have a small gear case lower unit on my Xr4 150. I need to find a prop to fit it. The prop I have on now has been modified to fit. My assumption is I need a 4.25 hub and the prop on now was ground down to clear the housing. Any help would be greatly appreciated. My engine serial # 0C267358 and lower unit # 1655-9572-c....Perhaps someone replaced the lower unit at one time with an older style? Thanks for the help!

 

[racerone]

Step #1 is to determine the pitch that you need to fit the BOAT and the conditions.---Then see a dealer as they can help you.

 

[mack4k]

I am thinking a 19 pitch...my dealer got me one and it is too long. I would really like to know what year lower unit I have. Thanks for the reply.

 

[racerone]

A google search says that gearcase is used on 1988 to 1990 ? models.------Some years they used 2 different gearcase numbers.

 

[QBhoy]

You’d imagine that the usual merc props for gearcase generally up to the 125hp size, might be the right fit ? Or am I being silly ?

 

[mack4k]

I wondered that also - Thinking I have a 4 1/4 gearcase. Not sure how to verify that?

 

[QBhoy]

I wondered that also - Thinking I have a 4 1/4 gearcase. Not sure how to verify that?

Just had a look. Yeah. Looks like it’s a 4 1/4 gearcase on that.

 

[Texasmark]

4 ¼ belongs to the 3-4 cylinder 2 strokers in the 75-125 HP range normally to name one area of useage. Merc. came out with this smaller gearcase in the higher HP applications for specific boats and usage. Props that fit that GC are 13 to 14.0" max...with some removal of the front of the trim tab for the prop to clear on the 14 and the clearance of the prop to Antivent plate is on the order of ¼".
So, in your quest, go to the section on the size I mentioned and you will find props galore.

 

[spiderdaddy72]

I have a 1992 merc 150 xr6.it to has the smaller gear case also. 1.78:1 gear ratio.i discovered it had a crack in it.im having trouble finding a lower unit for it.i think I'm going to a 1.87:1 .bigger gear case

 

[spiderdaddy72]

I have a 1992 merc 150 xr6.it to has the smaller gear case also. 1.78:1 gear ratio.i discovered it had a crack in it.im having trouble finding a lower unit for it.i think I'm going to a 1.87:1 .bigger gear case

It's a 2.5 6cyl

 

[Chris1956]

Merc and others made props for the 4+ 6 cylinder inline series of Mercury engines for a long time. These motors had the 4-1/4" gearcase. I would expect those would fit your motor, and are available in pitches up to at least 24".

I would specifically investigate props for a '78 or earlier 115HP motor, as that motor was real popular, has the 4-1/4 gearcase, and had the wide range of pitches. I would hope a dealer would have one of those for you to try out for fit.

 

[Texasmark]

I have a Ballistic SS 13 ¼ x 24, 15 tooth spline I was running on my stock 90 ELPT when I snapped the picture in my avatar. So high pitches are out there....iboats sells Ballistic.