Mercury motor swap

[Z28rs350]

Hi all, new to the site and looking forward to advise. I have a 1997 Bayliner 17 ft. With a 1997 115 hp Mercury motor. Motor has low compression and not worth rebuilding.
I have an excellent running 1982 90 Hp Mercury engine.
my question is does any one know if the tilt/trim unit and throttle controls from the 1997 Mercury will work on the 1982 90 Mercury the 1982 has the old 3 button trim control.
Thanks

Ken

 

[Chris1956]

The newer trim/tilt control will work with the older motor. Unplug the trim limit switch on the '82. Put a jumper wire across the trim limit switch connectors on the main trim harness. Now connect the blue trim wire to the up side of the new control, and the green wire to the down side of the trim control.

You will no longer have a trim limit switch, so it is up the the driver to stop trimming when the boat is trimmed properly.
If you have a trailer button on your newer control, you could wire it, using the trim limit switch. However, most of the trim limit switches broke long ago, in my experience.

 

[Z28rs350]

Thank you for the reply, so basically the trim/ tilt unit itself will work from the 97 motor on the 82? And the 97 controller box from the 97 should work on the 82 then?

 

[Texasmark]

Depending on the pitch of your transom, Trim positions are self limiting. Tucking in, the mechanical parts of the engine set the limit. Pushing out, when the prop starts ventilating, due to being too close to the surface, your speed will drop and RPMs increase....alerting you that you are as far up as is practical for the particular "setup" at the time. If your transom has a lot of pitch, the trim ram will run out of length, and the pump will unseat the overpressure valve in the unit before the prop gets close enough to the surface to ventilate. Holding the UP button down will not result in any increase in engine position.

 

[Z28rs350]

Thank you for the information

 

[Chris1956]

You may be misled. The PTT unit on your '82 is unique to motors of that 'svintage and older ones back to the 70s. The trim switch on your newer controller is compatible with the PTT unit on the '82.

I doubt any of the components of the '82 PTT unit will work on the newer motor, as they were pretty unique.

 

[Z28rs350]

Hi Thanks. So the controller from the new unit will work on the 82. Will the PTT unit from the new one work on the 82 as well ?

 

[Chris1956]

No, the PTT units are unique as are the transom brackets on each motor. I do not know if you could swap the transom brackets.

Not sure why you are asking these questions. The original question was about using the newer PTT switches on the old motor. That is a yes, as switches are pretty universal.

 

[Texasmark]

You may be misled. The PTT unit on your '82 is unique to motors of that 'svintage and older ones back to the 70s. The trim switch on your newer controller is compatible with the PTT unit on the '82.

I doubt any of the components of the '82 PTT unit will work on the newer motor, as they were pretty unique.

If you are commenting on my reply, he asked about the controller. I had an 850 with PTT and it had the pistons out on the brackets where Merc. first put shocks and are completely different from newer units with tilt and trim rams tucked between the transom clamp brackets. I don't recall the interface nor the model number of the control back then. My current reference is the '94-'05 manual on the 3-4 cyl engines of that HP range.