where to hook up water pressure gauge on 1997 Johnson 25 2-cyl.

[srimes]

Anyone know where to plumb in a new water pressure gauge on my 97 25hp 2 cylinder Johnson? The instructions show 40 hp and up OMC motors. I just bought the factory service manual and glancing in there I didn't see that specified. Also, once I do get it hooked up, what pressure should I see at WOT? Thanks.

 

[Haffiman]

Re: where to hook up water pressure gauge on 1997 Johnson 25 2-cyl.

A T-connection in the pee-hose.
I believe the pressure is about 30 PSI when the release valve starts to open which should be around 3000rpm. There are no official specs.

 

[srimes]

Re: where to hook up water pressure gauge on 1997 Johnson 25 2-cyl.

A T-connection in the pee-hose.

Well that makes it easy, thanks!

 

[srimes]

Re: where to hook up water pressure gauge on 1997 Johnson 25 2-cyl.

I hooked it up and get 0 psi at idle and only 8 psi at WOT. Are you sure it should be plumbed in there? Are these normal readings?

 

[Haffiman]

Re: where to hook up water pressure gauge on 1997 Johnson 25 2-cyl.

That is the place to hook it up, but!
It might depend on the outlet nipple in the exhaust cover. If that is the type with 'reduced' flow and no nipple at the end of the hose, you may have to replace the nipple in the cover to an 'older' version (or drill it up) and install the nipple #65 in below link at the end (outlet) of the hose moving the restriction to after the T-connector.

http://www.marineengine.com/parts/j...urer=Johnson&section=Cylinder+&+Crankcase

 

[Silvertip]

Re: where to hook up water pressure gauge on 1997 Johnson 25 2-cyl.

30 PSI is pretty high for that motor. Typical on thermostat controlled motors is about 15 - 17 PSI. If the impeller has not been changed in years, then your readings are probably normal. The idea with a WP gauge is to install a new impeller at the same time. You then take idle, mid range and WOT pressure readings and note them somewhere. Any deviation from those numbers down the line means the impeller is in need of service. So where the gauge is plumbed is not as important as what the readings are with a new impeller. My 40 HP was plumed into the tell tale and it worked fine. Some do and some don't. It just depends on the engine and the cooling system design.

 

[srimes]

Re: where to hook up water pressure gauge on 1997 Johnson 25 2-cyl.

nipple #65 in below link at the end (outlet) of the hose moving the restriction to after the T-connector.

http://www.marineengine.com/parts/j...facturer=Johnson?ion=Cylinder+&+Crankcase

Thanks! I just ordered the nipple along with a water pump repare kit. I already had an impeller but when I went to replace it I began to suspect that it still had the origional impeller! The shift linkage connection had good paint with no scuffs at all (until I disconnect it) and the lower unint bolts + nut were the same way! This is a 1997 model went fishing on the river quite frequently. It honestly didn't look too awful but the water pump plate was somewhat groved so I figgured I'd replace the whole thing as it was only $40. It'll be interesting to see what the pressure gauge shows once it's all replaced!