Johnson speedo pickup?

[Gary H NC]

Getting the new lower shipped to me for my( new to me) Boat.
I noticed there was no speedo pitot on the back of the transom and thought maybe it was taken off but see no holes.
The guy i'm getting the lower from sent me some pics and i noticed the trim tab had a hole,Is this a pickup for the speedo? If it is how does it work? 175 Johnson,1981 model.

 

[Esox]

Re: Johnson speedo pickup?

On my 150 the spedo pickup is at the front of the gearcase. About 2 inches above the propshaft centerline. Not sure about the hole in the trim tab.

 

[F_R]

Re: Johnson speedo pickup?

I donj't recall the purpose of the hole, but don't see how it could serve as a pitot, which has to be facing forward in undesturbed water. The trim tab, being behind the prop is anything else but undesturbed water.

 

[Gary H NC]

Re: Johnson speedo pickup?

Thats what i was thinking,the prop turbulence would mess that up. The old lower was so eaten away i can't tell by it..Guess i'll look over the new one when i get it.. Waiting on my manual also..

 

[Esox]

Re: Johnson speedo pickup?

The old lower was so eaten away i can't tell by it..

I saw the pictures of it. I've never seen a LU eaten away like that before.

 

[Gary H NC]

Re: Johnson speedo pickup?

It was NASTY!! from freshwater too
Believe it or not all the bolts come out no problem..

 

[tashasdaddy]

Re: Johnson speedo pickup?

i was glad of that. just put the regular old speedo on it. this is the fishing boat correct, or am i wrong. the other boat is the other kind of fishing boat. CAT fishing?

 

[Gary H NC]

Re: Johnson speedo pickup?

True TD, I'll pull the old speedo out of the dash and see how it hooks up.May just need to add the pitot and tube..

 

[Dhadley]

Re: Johnson speedo pickup?

That hole in the torque tab is to add water to the exhaust to cool the hub in the prop.

 

[tashasdaddy]

Re: Johnson speedo pickup?

the speedo, is the pitot, with hose attached that runs to the instrumtent on the dash. very simple it works of the pressure of the water, going into the small hole in the pitot, creating air pressure in the tube, and the instrument needle moves. basically it's an air pressure guage.

 

[Gary H NC]

Re: Johnson speedo pickup?

That hole in the torque tab is to add water to the exhaust to cool the hub in the prop.

OK...I understand that,Thanks Dhadley
TD,i guess at one time there may have been a plastic pitot on it.When i was looking at the wiring and control cables inside the transom i didn't see the speedo tube..Further investigation..