Question on shaft length and transom.

[ITGuy]

Ok...I read tons of posts and know I need a long shaft for my 20" transom. I picked up a older Johnson 10 hp that didn't seem to be a 15" or 20" shaft. It was kind of in between when I measured it at a bit over 18". Now my question is will this work on my boat with the 20" transom? I placed it on there and it looks to be within about an inch from the bottom of the transom. Also, when looking closely at the water intake at the bottom of the engine just above the rear part of the prop looks to be at the same height or just under the transom. I took some pics and was wondering what you guys think. Will this be too close? I did read that around an inch or so close would be fine, but being this is my first boat I would like opinions.

 

[bobberboy]

From the pics it looks like the cavitation plate is about even with the bottom of the boat. If that's so, you should be fine.

 

[Zum]

I always go up till it starts to handle bad(cavitate).
Just make sure it has a good water flow...pumping good,real important.

 

[ITGuy]

Thanks, Guys

Although, the pics look close it is not quite even with the transom. There is about 1" difference nearest to the transom and farther back seems to be even with the transom. I have read multiple posts and saw the diagram Zum posted many times. But, when measuring the motor it is a little more than 18" with how the diagram shows. I know I have read somewhere where there are mid shaft length engines that can work on both long and short shaft sometimes. I haven't put it in the water yet, but am thinking it should get plenty of flow. The water input is the little triangular thing just above the rear part of the prop.

 

[lckstckn2smknbrls]

looks good to me.

 

[Zum]

It looked fine to me also,propbably should of said that in my first post.
The waters that I fish are pretty shallow,with hard rocks,I just like to keep as much of
the motor out of harms way.

 

[bassboy1]

That is technically a short shaft engine. Back in the days that those were made, they were run a little deeper. For instance, my 1975 Evinrude 40 longshaft (well both of them, actually) is 23 inches. My 1975 Johnson 40 shortshaft is 18.

That idea was continued on the smaller motors on later. My 1988 Evinrude 4 Deluxe is also 18 inches to the main cav plate. It does have a smaller plate at 15 inches, where the bottom of the transom should be.

On the later/larger engines, where the cav plate should line up with the hull, you'll find the water intake is further down the sides of the lower, not on the torque tab behind the prop. Putting the inlets further down allows the motor to be run shallower for better performance. Way back when, especially on smaller motors, better performance wasn't the main goal.

Now, if it works, go for it. Just make sure you aren't ever loosing water flow.

 

[ITGuy]

Thanks, for every ones comments. I will be sure and watch the water flow. With the water intake being so low, it seems so close that I think it should work. I also found these pics of Transom and mount height on the net from a local marine store.