Speedo hookup for 1978 Johnson 75HP outboard

[PISTONESAL]

Can anybody tell me if there is a hookup on this motor for the speedo or do i have to buy a pitot? There was a speedo in the boat but no tubing going to the rear of boat. there was a piece cut off at speedo. Can anyway help?

Thanks

Sal

 

[tashasdaddy]

Re: Speedo hookup for 1978 Johnson 75HP outboard

you need tubing and pitot. watch ebay.

 

[Silvertip]

Re: Speedo hookup for 1978 Johnson 75HP outboard

No waiting and no shipping -- buy it at any store that sells boating supplies. Those things are almost dirt cheap.

 

[jay_merrill]

Re: Speedo hookup for 1978 Johnson 75HP outboard

Speedos don't "hook" to your engine, tachometers do. Unless you just need to fill a hole in your dash, I wouldn't bother with a water pressure driven speedo because that aren't very accurate. On the other hand, if you have an empty hole and no tach, by all means fill it with one because it is a very useful instrument.

For speed info, go buy a hand held GPS - you will probably be able to find one for 80 bucks or less. With this device, you can not only navigate, but you can detertime your speed accurately in either knots or statute mph. BTW, if you spend a little time comparing rpm settings for you motor with the speed readout on the GPS, you will be able to determine approximate speed most of the time, just by looking at the tach.

 

[ziemann]

Re: Speedo hookup for 1978 Johnson 75HP outboard

Jay- I agree with you that pitot/ pressure actuated Speedometers aren't all that accurate and a GPS is definately the way to go- BUT- there have been many outboards that have a pitot built in to the lower unit and the tubing for the speedometer DOES connect to the motor if you want to instead of having a seperate pitot. If a speedometer is tube connected to the outboard connection, you can see changes in pressure on the pitot based upon the trim of the outboard.

In this case, often a regular pitot can perform better than the connection on the outboard. But, as Jay said, a GPS is accurate- a pressure actuated speedometer can be effected by a ton of things creating inaccuracies....

 

[jay_merrill]

Re: Speedo hookup for 1978 Johnson 75HP outboard

That's interesting - I have never seen one installed on a motor. Then again, like most people, I know the motors that I have owned the best, so I'm not surprised at learning something new.

Just because I am curious, do you know which brand/models had this?

 

[ziemann]

Re: Speedo hookup for 1978 Johnson 75HP outboard

I have seen it on many models including OMC/ BRP larger outboards (my Johnson '05 carb'd 90 2 stroke has one) as well as larger Nissan/ Tohatsu outboards....

I cannot speak from experience on Mercs, Yamahas, or Hondas...

 

[Mscanon99]

Re: Speedo hookup for 1978 Johnson 75HP outboard

I had a 1999 Merc 115 that had the speedo pickup built into the lower unit. I now have a 1994 Evinrude that does not appear to have it as the spedo pickup is the separate transome mounted device, which is broken and I just paid 9.00 for an Evinrude branded unit. Will replace today just so I have a working dash guage, regardless of how accurate...I agree, GPS the way to go for accuracy.

Mike

 

[jay_merrill]

Re: Speedo hookup for 1978 Johnson 75HP outboard

Sounds like pitot tube molded into gearboxes is a recent sort of thing, which explains why I haven't seen them - I only fool with the old motors!

< jay runs outside to rub the cowl on his '72 johnson to put a little "keep on runnin' so well" mojo on it! >