1969 Glasspar outdrive swap out

[meantobe63]

Just purchased a 1969 Glasspar with 160hp Inline-6. Only thing missing is the outdrive. I have a 1969 Tom Sawyer with a 120hp inline-4 sitting here I was hoping I could slap the drive on to the Glasspar just to be able to lake test it. I know the ratio is not the same for the 4 and 6 cylinder engines, I'm just wondering if the shaft is the same length basically. Once I know boat is good, I'll go from there.

Additionally, how bad is it to re-prop the drive to be more suitable for the additional horsepower/torque? Don't really plan on beating this thing up, 30mph should be just fine. And of course I'll watch my RPM's..


Thank you.

 

[Eric 3.7LX Alpha 1]

in '69 the drive for each would be the MC-1 model.
The MCM120 used a 1.98:1 gear ratio in the drive.
The MCM160 used a 1.68:1 gear ratio in the drive.

Using the 1.98 on the 160 will cause it to increase in RPM and have a higher WOT. Keep an eye on the tach, might be able to get a way with a pitch change on the prop, others would know better than I do on how much.

My engine/drive combo used a 1.84:1 ratio. For a couple of seasons I ran it with a 1.65:1 ratio, I went the other way with lower gears, it bogged the engine down from throttle to about mid throttle. I could tell the difference and didn't push it. It got me by until I replaced it.

The shaft lengths were different for the newer drives, Alpha One uses a 18¾" length shaft, the MC-1 was 15½"
You would be used an MC-1 for both so should not be an issue there.

 

[Scott06]

Just purchased a 1969 Glasspar with 160hp Inline-6. Only thing missing is the outdrive. I have a 1969 Tom Sawyer with a 120hp inline-4 sitting here I was hoping I could slap the drive on to the Glasspar just to be able to lake test it. I know the ratio is not the same for the 4 and 6 cylinder engines, I'm just wondering if the shaft is the same length basically. Once I know boat is good, I'll go from there.

Additionally, how bad is it to re-prop the drive to be more suitable for the additional horsepower/torque? Don't really plan on beating this thing up, 30mph should be just fine. And of course I'll watch my RPM's..


Thank you.

as mentioned the drive will fit in as both of the inline engines will have same driveshaft length.
I also run a set up with a lower (higher numerical) drive ratio. I just stepped up in pitch 2” to overcome the steeper gearing. would Slap it on and see where your wot rpm lands , then reprop from there.

 

[meantobe63]

in '69 the drive for each would be the MC-1 model.
The MCM120 used a 1.98:1 gear ratio in the drive.
The MCM160 used a 1.68:1 gear ratio in the drive.

Using the 1.98 on the 160 will cause it to increase in RPM and have a higher WOT. Keep an eye on the tach, might be able to get a way with a pitch change on the prop, others would know better than I do on how much.

My engine/drive combo used a 1.84:1 ratio. For a couple of seasons I ran it with a 1.65:1 ratio, I went the other way with lower gears, it bogged the engine down from throttle to about mid throttle. I could tell the difference and didn't push it. It got me by until I replaced it.

The shaft lengths were different for the newer drives, Alpha One uses a 18¾" length shaft, the MC-1 was 15½"
You would be used an MC-1 for both so should not be an issue there.

The boat came with a prop but no drive, haha. Prop in it was a 21 pitch and the prop on the 12 was a 17 but might have been a little much since I couldn't get above 3500rpm with it. But if the 160 ran correctly with a 21 I'd guess I'd need like a 25 pitch on the 1.98.

Thank you Eric.

 

[meantobe63]

as mentioned the drive will fit in as both of the inline engines will have same driveshaft length.
I also run a set up with a lower (higher numerical) drive ratio. I just stepped up in pitch 2” to overcome the steeper gearing. would Slap it on and see where your wot rpm lands , then reprop from there.

Thanks Scott. Sounds like a plan. Since I don't know if the 21 was correct for the boat, I'll throw it on the 1.98 and go from there with the pitch calculator.

 

[kenny nunez]

Measure the inside of the lower gimbal ring where the drive rests in the down position and the width of the drive you are going to use. They should be the same. Later model drives had a wider spacing at that point.

 

[meantobe63]

Man, what a PAIN it was to install a drive that came right out of a bellhousing and right in (new o-rings and gaskets of course) to one that hasn't had one in 13+ years and exposed to moisture that entire time. Splines got in to the coupler fairly easy but when it was time for the last 1.25" basically with the gimbal, my god what a pain. But It's on and installed and checks out. Going to head to lake and test it out. Unfortunately the Tach decided to stop working while running it on hose so I am hoping it'll work this evening so I can pick a different prop. The one I have on it now is a 14" 3-blade stainless 19P.

 

[nola mike]

Did you check the alignment prior to install?