Switching Motors

[The twoms]

I am looking at a boat that has a bad force motor on it. Plus I have a 1979 18 ft glasstron that needs a lot of interior work but has a good 1981 140 Johson on it. If I switch motors what am I looking at? How many new holes will I have to drill and plug on each boat? Will it effect the structure of the transoms? Should the steering be the same? What am I not considering?

 

[imported_JD__]

Re: Switching Motors

MJK,<br />I'm no mechanic but recently changed from a Merc 115 2-stroke to a Johnson 140 4-stroke, did it myself. Can't get into specifics but the major changes I had to make was cabling, controls and wiring harness. Merc trim gauge is different from Johnson also. I had to modify the panel that the control attaches to, actually welded a piece over it, re-cut it out and re-carpeted. It wasn't all that bad, I actually enjoyed it. My Johnson bolted right up to the Merc bolt pattern.<br />JD

 

[The twoms]

Re: Switching Motors

Sounds good to me. Does anyone know if the bolt patterns are the same on a 1992 Force 90 HP and a 1981 Johnson 140?

 

[Solittle]

Re: Switching Motors

Can't help on the conversion but you will be overjoyed at the difference in performance. The rig should fly. I had a 140 on a 19'er long time ago.

 

[JB]

Re: Switching Motors

What is the "new" boat rated for. If it has a 90 on it 140 may be too much.<br /><br />If you use a fixed setback plate you don't have to drill or plug any holes at all (except on the setback plate).

 

[The twoms]

Re: Switching Motors

The newer boat is only rated up to 120. Do you think 140 is too much? I don't understand how they rate boats. The older boat which has the 140 and rated for up to 140 is 17.5 feet long while the newer boat is 18 feet long but only rated up to 120. Also, when did OMC start rating at the prop instead of the power head? Isn't a 1981 140 Johnson about equal to a newer 112 HP?

 

[Solittle]

Re: Switching Motors

mjk - The thing to be concerned about is not which boat is rated for which motor or when the hp ratings changed, it is the legal liability that will fall on your sholders if you ever have an accident/incident with an overpowered boat (according to the manufacturer - not you or us). Lawyers love that situation.