1987 Johnson GT150 water psi gauge install

[Ranger 330V]

On an 87 Johnson GT150...where do I install the water psi gauge?? Do I tee into the tell tale?? Or is there a place in the water jacket to install?? Hoping not to have to drill and tap. Thanks alot!!

 

[Ranger 330V]

Re: 1987 Johnson GT150 water psi gauge install

ttt

 

[emdsapmgr]

Re: 1987 Johnson GT150 water psi gauge install

I run mine exlusively off the telltale fitting on the back of the exhaust cover-with no telltale. If you tee it into the telltale line, you may find the gauge pressure reads somewhat lower, as some pressure will bleed off through the telltale. You can experiment with it and see which you prefer.

 

[Ranger 330V]

Re: 1987 Johnson GT150 water psi gauge install

The water goes to the tell tale before or after the powerhead?? The water never gets very warm so I'm thinking before?? I know on mercs its after the powerhead and can get very warm. Will this show me if I'm losing a pump (low psi) and if I have a clog somewhere in the power head (high psi) these compared to normal of course?? Thanks alot!! Hope to install one in the next few weeks.

 

[emdsapmgr]

Re: 1987 Johnson GT150 water psi gauge install

The water first fills the exhaust cover, then into the heads and out the adapter, so the telltale is one of the first to receive water. These engines tend to idle between 6-8 and can run up to 16-18 at full speed. Low water pressure at idle can be an indicator of a weak pump. My crossflow experience is that I replace impellers more due to their age than because they wore out and the idle/running pressue got too low. You can still overheat one (or both) side(s), with a normal water pressure reading, so you may want to consider adding a temp gauge also.

 

[Ranger 330V]

Re: 1987 Johnson GT150 water psi gauge install

Would you do water temp?? or cylinder head temp?? I know there are two heads...I do have a head temp gauge sitting at home...where would you put the temp gauge sender?? I really need to get a manual for this motor...I've got one for my old 140 xflow...thanks again. I want to keep the old girl running dependably...she's an 87 and NEVER had a head bolt turned.

 

[iwombat]

Re: 1987 Johnson GT150 water psi gauge install

I think it's better to measure cylinder head temp. That's what you really want to know anyway. Water temp is only measuring the next-best thing.

 

[emdsapmgr]

Re: 1987 Johnson GT150 water psi gauge install

You can run a temp gauge to register either cyl head temp or exhaust cover temp. I agree with Wombat. I run one off of the starboard head only. This should be fine for recreational purposes. Technically, is suppose you could run two gauges, one for each head, but that may be for the racing guys. I do laser gun the engine periodically to make sure both heads are cooling properly. You can make an "L" standoff bracket that will hold the temp sender in contact with a the head. Bolt it to one of the small head cover bolts.