Lower unit compatibility

[Jjust61]

I have a 1984 150 Blackmax that needs a lower unit. Can someone tell which other engine lower units and year models are compatible with this. Thanks in advance

 

[Chris1956]

Why not go on the SEI website and see what gearcase models fit your motor, as well as other models? It is likely that V6 gearcases from the late 70's to the early 2000s will fit, but you need to check. You will want to know your gear ratio. 2::1 is most common, but there are others as well.

Do you have the 4-1/4" gearcase or the larger 4-3/4" gearcase?

 

[Dukedog]

any 2.0, 2.4, 2.5 V6 gearcase from '76 ta way up in tha 2000's will bolt up if same length as yours.. ratio's will be either 2 ta 1's (2.0 150's) or 1.87 ta 1.. except tha 4 1/4 inch "small case" which will be 1.78 ta one.. but they all will fit.................

 

[Chris1956]

It is probably best to retain your gear ratio and gearcase size. Merc driveshaft length are usually not adjustable. So you need to order the correct driveshaft length and ratio plus the size of the gearcase. On an unusual event, I had swapped a 1993 Merc V6 25" 5" extension for a 20" gearcase. It had an extension kit to extend it to 25" I pulled off the water tube extensions, the cast extensions, These was a 5" steel extension to the drive shaft. however, you should not expect it.

 

[Dukedog]

your case is a 2 ta one.. if you buy used ya will need ta know how to determines what tha ratio is by turns of tha drive shaft to turns of tha prop shaft.. tha drive shaft wiil turn 2 revolutions to1 prop shaft revolution.. your serial number doesn't give shaft length but would guess a 20"?...

 

[Jjust61]

Why not go on the SEI website and see what gearcase models fit your motor, as well as other models? It is likely that V6 gearcases from the late 70's to the early 2000s will fit, but you need to check. You will want to know your gear ratio. 2::1 is most common, but there are others as well.

Do you have the 4-1/4" gearcase or the larger 4-3/4" gearcase?

Inside diameter of the gear housing is 4 1/4”.

 

[Jjust61]

Inside diameter of the gear housing is 4 1/4”.

Also, not familiar with sei website. Can you send link? Thanks

 

[Jjust61]

any 2.0, 2.4, 2.5 V6 gearcase from '76 ta way up in tha 2000's will bolt up if same length as yours.. ratio's will be either 2 ta 1's (2.0 150's) or 1.87 ta 1.. except tha 4 1/4 inch "small case" which will be 1.78 ta one.. but they all will fit.................

Thanks. Is the 4 1/4” gear case the inside diameter of the case?

 

[Chris1956]

Sterndrive Engineering: For Mercury / Mariner / Force Outboard Complete Lower Unit Applications

 

[Dukedog]

if its tha small case it was changed somewhere down tha line.. 4 1/4" outside ta outside... tha small case only came on tha XR4 and 6... it will also be a 1.78 ta 1 gear.. if your rig is propped for that ratio and hub size it may present a slight problem with performance with any other ratio and size.......... don't think sei does tha small hub case?

can you get a picture of tha side view of tha case?