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  1. #1

    Default trim sending unit and water pressure

    I installed a new trim gauge on my boat. I have a 1988 Johnson 88 spl. I wired the gauge just as the instructions said one wire from the sending unit and a ground to the ground post on the gauge the other wire from the sending unit to the S post and a hot wire to the I post on the gauge. The trim gauge works but as soon as I start to raise the motor the needle goes all the way up. It's like there is no travel on the sending unit only a small spot where it works. Is this the sending unit or do I need a resistor in line somewhere. Also installed a water pressure gauge. i have zero pressure with a hose hooked up in driveway at idle. The gauge is a 30 psi. still need to put it in the water and test it out at speed. The tattletale is spitting water at idle. Any input on these 2 items will be appreciated.

  2. #2
    Chief Petty Officer toddschubert's Avatar
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    Default Re: trim sending unit and water pressure

    I have an 88spl that I love and it does the same thing on the trim sender. I't not the guage. I think the sender is designed to only work in trim position only but there is a grey area there. My gauge stays all the way up untill I get to almost mid point then it kicks in. It used to bother me but like others have said We trim by feel, rpm, speed, sound. The gauge means little.
    I'm curios why you put a water pressure gauge in. and where did you hook sender?
    It's a possibility!
    Love my '93 88spl Johnson and '93 Larson bow rider

  3. #3

    Default Re: trim sending unit and water pressure

    The sending line tee's in the water jacket where the tattle tale hose comes off the power head. This motor had a pressure gauge on the boat it came off of. I figured if I have this gauge on my boat i will know that I have water circulation without having to constantly checking the tattle tale for water flow.

  4. #4
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    Default Re: trim sending unit and water pressure

    The trim sender and gauge can be checked easily: Disconnect the trim sender and connect various resistors instaed. 94 Ohms should show downmost position on the gauge, 46 Ohms center position, and 0 Ohms upmost position. These are the values I checked out with my 1989 60hp when I was looking for a new trim sender's potentiometer.

  5. #5

    Default Re: trim sending unit and water pressure

    Also, with the trim sender disconnected you should be able to check the resistance with a multi-meter. As the sender travels through it's range of motion the resistance should vary smoothly.

    Another thought - are you positive the gauge you bought is for a JohnnyRude? If by chance it's for a Merc it won't work.

  6. #6
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    Default Re: trim sending unit and water pressure

    If you trim the motor up, you should see the black plastic trim sender. You might move it with your hand and see if you get deflection on the meter. BTW - it is much better to trim by feel and sound than by a gauge.

    I think you should be seeing much more pressure on that gauge. Sometimes there is a threaded plug on one of the cylinder heads. This is a good place to put the presure gauge.

  7. #7

    Default Re: trim sending unit and water pressure

    The gauges are Teleflex made for Johnson and Evanrude. I don't have any resistors but I do have a meter to test with. Going out of town for a couple days I'll check this out with my meter when I get back. Also i am taped in to the threaded plug on the cylinder head same place the discharge for the tattle tale is.I'm thinking the water pump may need to be rebuilt.

  8. #8
    Chief Petty Officer toddschubert's Avatar
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    Default Re: trim sending unit and water pressure

    My "93 88spl has tell tail coming out of power head cover between heads. That may be a year issue but the pressure in my whole system seems low and I just rebuilt it from the pump up. I'm thinking again this is an inherent issue with that motor not necessarily a problem. The thermostat housing design allows for some pretty free flowing water. You might want to take it off and check for debris also head cover plate. see my thread http://forums.iboats.com/johnson-evinrude-outboards/ok-trusty-iboaters-my-88spl-johnson-cyl-1-3-running-170-175-hot-2-4-norm-148-whatsup-524155.html
    It's a possibility!
    Love my '93 88spl Johnson and '93 Larson bow rider

  9. #9
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    Default Re: trim sending unit and water pressure

    If you can see the top of the motor(s), a trim gauge is just a waste of panel space. When I repowered my 23' GW Gulfstream with T 175HP E-Tecs, the trim gauges were the first to go. Just not necessary at all.
    Jim

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  10. #10
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    Default Re: trim sending unit and water pressure

    The trim sender is designed to show the position of the engine when it is in the trim range only. That means that when the midsection is resting on the two trim rams, the gauge should register. When the trim goes into the "tilt" range (higher than the two trim rams,) the sender arm loses contact with the swivel bracket and the gauge should continue to register that the engine is all the way up. The sender unit is adjustable to a certain degree. You can loosen the two screws holding the sender and move it a few degrees in order that it's signal will match the range of the gauge. You may have an issue with the telltale. It could be plugged somewhat or your impeller may be bad. You should see a strong, steady flow from the telltale nozzle in the lower cowling at all times. You should see 4-6 lbs at idle and over 15-16 lbs at full speed on the gauge.

  11. #11
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    Default Re: trim sending unit and water pressure

    i also think a trim gauges isnt worth the headache and panel space.....you are going to trim watching the rpms and the posture of the boat!!...

    if you only ran your boat on flat water...the gauge may have helped just a little....but conditions are so varied...you wont have a setting to just dial in most times...

    I have done this:

    trim all the way in...then hit the trim up button and count 3 seconds or 5 seconds...try that a few times and fine out how many seconds you need to hold the trim buttom to get to where you remember you were running good...that way you can look at other guages, like speed, water pressure or rpms.

    teh loading of the boat, and water conditions may change those seconds, just like they change the trim angle reading .

    thos eunits are so flimsy they always seem to be broke...but if it already works and you have the guage, then leave it!!

    bob

  12. #12

    Default Re: trim sending unit and water pressure

    My trim sender has a lot of travel so I'm thinking it's this sending unit. No big deal about the gauge being perfect but I will test it at the end of the week when I'm back in town.The water pressure does have me concerned the water does flow out the tell tale but no pressure shows up on gauge at idle I will take my boat out at weeks end and try out at speed in the water.I really don't know how to change the water pump or impeller. May need some advice on that.

  13. #13
    Chief Petty Officer toddschubert's Avatar
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    Default Re: trim sending unit and water pressure

    Help is a click away. I just changed my water pump on 88spl. Not much to it if you know a few tips.
    It's a possibility!
    Love my '93 88spl Johnson and '93 Larson bow rider

  14. #14

    Default Re: trim sending unit and water pressure

    took my boat out today water pressure gets to 8psi at wot.I am concerned about this.Not worried about the trim gauge i think a new sending will fix that down the line. I also put a new tachometer in an must of read the instructions wrong reading way to many rpms. Does anyone know about what rpm idle is and wot should be?

  15. #15
    Chief Petty Officer toddschubert's Avatar
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    Default Re: trim sending unit and water pressure

    my 88 spl runs at 1000 idle 5000 wot with just me low fuel and trimmed up as high as can go w/o porpoising and boat dependant i might add a wopping 35mph
    It's a possibility!
    Love my '93 88spl Johnson and '93 Larson bow rider

  16. #16

    Default Re: trim sending unit and water pressure

    thanks Todd for that info You have been a big help I'll update next week

  17. #17
    Chief Petty Officer toddschubert's Avatar
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    Default Re: trim sending unit and water pressure

    Anything for a fellow saints fan
    It's a possibility!
    Love my '93 88spl Johnson and '93 Larson bow rider

  18. #18
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    Default Re: trim sending unit and water pressure

    The engine should idle smoothly between 650 and 700 rpm. Set the idle when the boat is floating normally at rest in the water, and the engine is in forward gear. You can't set the idle on the trailer. Your engine should run up to 5500+ at full throttle. The pointer on the back of the tach should be set to the number 6 for correct rpm reading. 8 psi is not enough to keep that engine cool at wot. Any chance the gauge is not working properly?

  19. #19

    Default Re: trim sending unit and water pressure

    the gauge is brand new. thanks for the info on the tachometer i have to check that setting first It goes over 7000rpm @wot and 2000rpm at idle.

  20. #20
    Chief Petty Officer toddschubert's Avatar
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    Default Re: trim sending unit and water pressure

    thats got to be wrong. Motor would "come apart" at 7000 rpm" and you would damage gearcase shifting at 2000 rpm regularly
    It's a possibility!
    Love my '93 88spl Johnson and '93 Larson bow rider

  21. #21
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    Default Re: trim sending unit and water pressure

    The tach must be set on the wrong setting...

  22. #22

    Default Re: trim sending unit and water pressure

    yes I think that it is on the wrong setting going to pull it out the dash an check it on Monday

  23. #23
    Supreme Mariner Silvertip's Avatar
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    Default Re: trim sending unit and water pressure

    The tach should have the pulse setting at "6" (you have a 12 pole alternator which produces 6 pulses per engine rev.) The instructions should have clearly pointed that out.

  24. #24

    Default Re: trim sending unit and water pressure

    That info is a big help. Didn't know its a 12 pole alternator Thanks a lot.

  25. #25
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    Default Re: trim sending unit and water pressure

    get an infared thermometer!!!!!!!! fast.... if you are really only getting 8 psi....you could ruin your motor fast......check your head temps while idleing for 15 minutes...just to make sure the motor isnt overheating at idle...then run the motor at maybe 3000 rpm for 1 or 2 minutes then check the head temps....

    if good run at 5000 rpm for 1 minute then check the temps...

    thats if you dont have a temp guage( which i highly recomend)

    bob

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