85ETLR78C tailtell and water gauge question. And 2 genral questions.

[lilroud]

Hey guys, been reading around on here past few day, good stuff. Recently I bought a 16 foot Stratos boat with a 1978 85 HP Johnson outboard for a good deal (First boat so bare with me). I have rebuilt the carb, changed the impeller and had the lower unit resealed, and been doing some other stuff cause none of the gauges were hooked up. Got all the gauges powered up and the tach gauge working. The one gauge I really would like to work is the water pressure gauge. I t'ed into the pee line and its a 30 psi gauge. It only registers like 1 psi, if i plug the pee line with my finger it goes up to 5ish psi at idle... here are my questions:

1.) can i just plug the pee line so I can just rely on my gauge?
2.) trim gauge... it has power... I found the sender unit for in in the left side of the trim assembly with 2 wires coming from it. Do I ground one of the wires and the other wire go to signal place on trim gauge?
3.)I noticed the spark plugs in it were QL78YC and my motor calls for L77JC4 or QL77JC4. How would this affect motor operation and should I change them?

Thank you so much in advanced!

Robert

 

[emdsapmgr]

Re: 85ETLR78C tailtell and water gauge question. And 2 genral questions.

When I install water pressure gauges, I remove the telltale and plumb the new gauge direct to the nylon hose barb on the back of the engine. There is some question as to a pressure difference in the gauge if it is teed in or not. It may read a little lower if it is teed into the line. You should get 4-7 lbs at idle and perhaps 17-19 when running at WOT. Sounds as if the line is plugged/restricted-a common problem. If the telltale is not strong, you can blow pressurized air back trough the nylon hose barb to clear it while the engine runs. (You may have to unscrew it and check it for flow.) I'd run the plugs that the factory recommends: QL77JC4. The QL78 plugs are for the newer looper V4 engines. Your engine has a remotely-mounted trim box under the rear splashwell. There is a terminal bar in that box. The two trim sender leads connect as follows: One to the "G" terminal (which goes to the - terminal on the battery), the other lead goes to the terminal to the right of terminal G-there should be a yellow wire on that terminal (a hot from the key switch.) Then run two new leads to the gauge from both of these terminals. When new, the factory pasted a color trim system wiring diagram on the inside of the box cover. Hopefully, it is still there.

 

[lilroud]

Re: 85ETLR78C tailtell and water gauge question. And 2 genral questions.

OK thanks for the response. Yeah the box is there, the inside is a mess with electrical tape and what not, ill look at it later this week. One more question. The trim sender: is there a way to check it before wiring to see if it works, could I ohm it out? Thanks

 

[lilroud]

Re: 85ETLR78C tailtell and water gauge question. And 2 genral questions.

cause i put a ohm meter on the 2 wires coming from the sender and it read infinate... and as far as the water pressure gauge the hose that goes to the gauge is tiny compaired to the nylon one for the telltale, its about the size of a float pin in a carburator. Would that possibly be why the reading is so weak cause the telltail has a inner diamiter that is so much bigger? thanks

 

[Silvertip]

Re: 85ETLR78C tailtell and water gauge question. And 2 genral questions.

Pressure has nothing to do with diameter. You have a cooling system issue that needs to be corrected, or you have an inaccurate gauge. Any pressure gauge can be used to verify. How well a water pressure gauge works depends on the design of the cooling system. Some systems register very low pressure until the thermostat opens. Other work fine regardless. Ideally you want the gauged plumbed directly to the cooling system rather than the tell tale.

 

[emdsapmgr]

Re: 85ETLR78C tailtell and water gauge question. And 2 genral questions.

When the trim gauge is in the full trim-in position, you should get an ohm reading of 82-88 ohms. When in the full tilt position, it should read 0 to 10 ohms.