Engine Mounting Brackets Primer

[Capt. Bob]

Often asked subject when re-powering. These were dug up while sorting through topics.

From Fitz7322

Here's some history-
The original OMC (Johnson/Evinrude) bolt pattern actually dates back to 1959 with the introduction of the V4 50 HP. Engines produced between 1959-1972, 50hp and up, utilized a set of slide in brackets that stayed permanently mounted to the boat and two cross pins held the engine in place. Come winter or for what ever reason the engine needed to be removed; you removed the cross pins and hoisted the engine off. slide brackets remain. Come 1973, OMC redesigned the mounting brackets and kept the bolt pattern. So hence, the slide in brackets were gone and the current form of mounting system became standard including V6's in 1976. Mercury and Chrysler had their own unique bolt patterns that made it difficult to change from OMC to their brand without re-drilling and filling the OMC holes. Someone at Mercury figured out that the way to sell more outboards was to match OMC's bolt pattern and beginning on or about 1979 Mercury matched OMC's pattern, then Chrysler/ Force and Yamaha in 83'. So every outboard today and models produced in the last 25+/- years has the original OMC bolt pattern dating back to '59. (Not sure about the new giant 300 hp+ engines, but for this discussion it doesn't matter) The point is; if you want to switch to another engine that was produced since the early 80's; the holes will line up. Of course; controls, harnesses, shift and throttle cables are different between brands with the exception of Johnson or Evinrude which are identical engines except for paint color and trim. So there is the history of the bolt holes and why they are that pattern.

A link from the Continous Wave site
http://continuouswave.com/whaler/reference/FAQ/#Q9

Etec and THT (.pdf) links:
http://www.etecownersgroup.com/post/15H ... ts-4754160

http://www.thehulltruth.com/attachments/boating-forum/207437d1323350040-outboard-mounting-template-help-backing-plate.pdf

[wingtime]

I hate to add to one exception of this...  I had a 89 Force and it did NOT have a standard bolt pattern.  The Force Motors built after Mercury bought them probably had a standard mount.

[fitz73222]

Bruce,

You are correct, The earlier US Force engines were still using the Chrysler castings until Mercury aquired them and changed the bolt patterns. Thanks for the correction.