Hydro-Mech Lower Unit ID questions

[JasonB]

Ok, I'll give this its own post.<br /><br />Is there an easy way to tell a Hydro-Mechanical ('73-'77 v4 except '77 135/140) from a later mechanical case visually? I have a line on a couple possible used lowers, but the owner isn't sure what year they came from.<br /><br />I know the following:<br /><br />1. My '76 85hp has two outlets on the waterpump. Is this a definite mark of a hydro-mech? It seems all the mechanical units I see are single outlet.<br /><br />2. I know the hydro shifts backwards from the mechanicals. I don't have access to my boat at the moment to check which way the linkage moves. Can someone give me a description I can give the owner that will help him check which model he has? Ie. if the shaft is up, the propshaft should turn clockwise, but not counter-clockwise (guessing here)<br /><br />3. are there any other visual clues I can use? I thought the skegs were a tell-tale, but looks like they aren't after looking further.

 

[Dhadley]

Re: Hydro-Mech Lower Unit ID questions

The bolt pattern and/or overall length. I'd go by the bolt pattern to be positive. Measure between the front bolt hole and the next one. <br /><br />BTW -- those two "outlets" on the pump, one is a return.

 

[JasonB]

Re: Hydro-Mech Lower Unit ID questions

Thanks DHadley. I'll have to pull mine to measure the bolt holes. The height of one of the units is 18" from tip of skeg to the mating surface of the unit, or are yoiu referring from the tip of the vent plate to the tip of the front of the unit?

 

[xikxak]

Re: Hydro-Mech Lower Unit ID questions

just checked my hydro-mechanical. shift rod down is fwd,up is reverse.of course without power it is very hard to move the shift rod.

 

[Dhadley]

Re: Hydro-Mech Lower Unit ID questions

There are two bolts on each side that attach the lower unit to the midsection. Measure the distance between those 2 bolts or bolt holes on either side. Any gearcase that will work on your 1976 midsection will have that same bolt spacing. A newer unit will have bolts further apart. Therefore it will not bolt up.

 

[McGR]

Re: Hydro-Mech Lower Unit ID questions

I'm fairly sure if it's got the two hole water pump housing and a shift rod, it's a hydro-mechanical. I believe all other L/Us with the two hole housing were electric shifts, which would not have a shift rod. To the best of my knowledge the skeg is different also. The purely mechanical L/U skegs look more swept back or angular when compared to the earlier V4 gear cases. I have the same motor as you and these are the conclusions I have reached.

 

[seahorse5]

Re: Hydro-Mech Lower Unit ID questions

Look at the shift rods. The mechanical shift has a flattened tip with a hole thru it for the shift retainer pin.<br /><br />The Hydro-mechanical shift rod is threaded at the top for the large diameter fitting with the hole and plastic bushing inside it.

 

[Dhadley]

Re: Hydro-Mech Lower Unit ID questions

But remember that the 1977 140 has the screw on fitting (barrel) at the top but the bolt pattern for mounting the gearcase is different. Overall the case is longer.

 

[xikxak]

Re: Hydro-Mech Lower Unit ID questions

As I posted on another board,wouldn't it be great if they put the model number on the lower unit as well as the motor so you could identify and avoid all this guessing.

 

[Dhadley]

Re: Hydro-Mech Lower Unit ID questions

Model numbers arent needed. There are only a few differences. All the early models will interchange and most all the late models will interchange. All V4's from 1978 on and some from 77 have the same bolt pattern as V6's and V8's. <br /><br />Regardless of skeg shape, inlet screen style, relief hole shape etc. the determining factor is the bolt pattern of the 4 mounting bolts. If the bolt pattern is the same, it can be made to work.