Alpha ID ?

[starsnstripers]

Serial # OB 588953 Year? And it came off a 488 4cyl But not sure of the ratio. It seems like two shaft revolutions to one prop revolution. Couldn't see the letter on the splined yoke nor do i know the location it would be on the Yoke. Any help would be great thanks

 

[ErieRon]

Re: Alpha ID ?

Pretty sure that's a 470 with a 4bbl carb, and I think it was only made in 1983-1984. Your serial number looks more like it's a model 180 from 1987. Wish I could say 100%, but someone will know and tell you shortly.

 

[ziggy]

Re: Alpha ID ?

well, i didn't write this and don't remember who did. thanks to them. but it may help...


How do I check gear drive ratio?

Do all these steps in order.
1. Shut off the battery switch
2. Pull the spark plugs out of the engine.
3. Put the shifter in forward.
4. Turn the engine till the prop starts turning, continue turning till the timing mark is at TDC.
5. Put a mark on the prop hub and the drive housing that align with each other.
6. Turn the engine by hand while someone watches the marks on the prop, and count the revolutions the crankshaft makes to turn the prop 1 complete revolution.
7. If it took 1.5 revolutions of the crankshaft, then you have a drive ratio of 1.5:1 which is what is needed for a small block V8. (a 260).

also, i've got a drive ratio chart. that says a 488 is 1.65:1 then in the next column which i think is notes. it says, F=1.5:1 i don't know what that means about the F. but thats what it says...

good luck..

edit. figured out the F. it's not relivant to yours.

but it also says..
letter stamped on the universal joint splined yoke
(new or untampered with drive units)
refer to s/b 91-21

this is a chart
------------Alpha------
17/28 -------13/21 -------- 14/28
B=1.98:1 --- B=1.94:1 ------K=2.40:1
D=1.84:1 ----D=1.81:1 -----A=2.00:1
C=1.65:1 --- C=1.62:1
F=1.50:1---- F=1.47:1
H=1.32:1 --- H=1.30:1

edit again.
go here to see s/b 91-21...http://www.boatfix.com/merc/mainmenu.pdf
thanks to dons as usual...

 

[starsnstripers]

Re: Alpha ID ?

Geesh I dont recall if the motor had a 4 barrel on it. It said 488 on the valve cover and was 4 cyl. I have the boat and drive but left the motor behind as junk. Who knows if they had the right drive 1.65:1 on it? Yeah Zig i saw that the 488 has a 1.65 but i'm trying to make sure the ratio because i'm going to repower the boat anyway. I'm getting 2 shaft revolutions to i prop revolution. That engine was to small anyway for a 23.5' Slickcraft at 3000 lbs

 

[starsnstripers]

Re: Alpha ID ?

I cleaned the yoked spline and no letter. Maybe an after market spline or a replacement. Do you know exactly where in the yoke it's located? thanks

 

[starsnstripers]

Re: Alpha ID ?

The other thing is all the serial #s I've seen in reference Start with OD mine is OB ?

 

[starsnstripers]

Re: Alpha ID ?

Anyone able to reference that serial# to a yr? I double checked and the shaft turns exactly 2 turns to one prop rev.

 

[Bt Doctur]

Re: Alpha ID ?

to be positive, pull the gears out and count the teeth
1.98 is 20/24
1.65 is 24/22

 

[ErieRon]

Re: Alpha ID ?

Give this a latch...

Count the gear teeth of the driven gear and the drive gear. The driven gear is attached to the upper drive shaft. The drive gear is attached to the end of the yoke (u-joint) shaft.

Drive/Driven;

17/19 = 1.84:1
24/24 = 1.65:1
20/24 = 1.98:1

Also, most are stamped on the side of the drive (i.e 1.65R)

Here's a couple of links for reference.

http://www.4shared.com/file/113521134/81eff60b/sterndrive_ratio.html

http://www.4shared.com/get/11352012..._engine_drive_model_year_reference_chart.html

 

[starsnstripers]

Re: Alpha ID ?

Thanks Doc, It was bolted up to a 3.7 and should be a 1.81:1 I think i'm going to put a 4.3 in it which also takes the 1.81:1. I didn't want to take it apart to check the ratio. If i take the top cover off can i just count the teeth in the uppers or?

 

[starsnstripers]

Re: Alpha ID ?

Thanks Ron, good links. I think it might be a High Altitude drive 2.0:1 Still wondering the year by way of the Serial#? OB 588953

 

[ErieRon]

Re: Alpha ID ?

You know, here's the problem; I've had two drives stolen in 24 years. The last time I bought a "brand new" one (insurance paid) through a certified mercruiser "silver service award" (or some crap) and they put on a drive that was some mish-mash of components that doesn't correlate to anything Merc. has published. The serial number doesn't make sense, the ratio stamped on the decal went from 1.84 to 1.62, and it has a decal that says "counter rotating drive". I finally went to another service facility, and by the time he was done explaining what I had, my head had already exploded. Point being...with a drive that old, you just don't know what you have unless you check it for yourself (count the gears). There's a protocol for rebuilding them and marking them correctly, and I don't think everyone follows it.

Bottom line, yes, you can count the gear teeth through the top cover...on mine at least.

 

[starsnstripers]

Re: Alpha ID ?

I hear ya Ron, I'll have to do that. My serial # is weird too. Everyone i've seen on here starts with "OD" Mine starts with "OB" no clue! lol Thanks for the advice Ron.