engine mounting holes - are they standardized?

[rbhankins001]

I am replacing a 2001 Johnson 175 hp 2 stroke with a 2007 F150 yamaha. Will the holes match up (I hope!) ? The boat is a 2001 Cape Horn 19. Thanks guys!

[Taken Lightly]

My boat is a 2002 and I was told that Outboards use the same standardized mounting holes.

[1outboard]

They the same ....since 1969.

[Boatdood]

They are the same pattern, but not quite the same size. American made outboards use a 1/2" bolt, the Japanese use a metric size. Close but just a bit smaller. It's simple enough to drill the hole larger.

For the record, mounting patterns were all over the place right on up until Yamaha entered the market in 1984. Yamaha had the good marketing sense to go with the most popular hole pattern used by OMC. Mercury followed suit along the same time frame, but Force engines used a funky mounting pattern and size for a while longer before finally getting on board. It's interesting to me that the entire industry in the U.S. now follows a pattern originated by a defunct company. OMC, or Johnson and Evinrude engines used to comprise over seventy percent of the outboard market in the U.S., similar to the semi monopoly Yamaha now enjoys. Who would have guessed they would bite the bullet.

[jethro1]

Boatdood - 2/10/2007 7:26 PM

They are the same pattern, but not quite the same size. American made outboards use a 1/2" bolt, the Japanese use a metric size. Close but just a bit smaller. It's simple enough to drill the hole larger.

If the bolt used by Yamaha is smaller than the ones used by Merc and OMC, why would you need to enlarge the hole for the Yamaha bolt?

[Tom W Clark]

Yamaha outboards use 1/2" mounting bolts. Same bolt diameter, same hole size.

The mounting bolt hole pattern is BIA standard which has been in effect since the early 1980s. It is derived from the OMC (now BRP) pattern used on their large outboards as far back as the late 1960s.

Yamaha outboards got their foothold by copying OMC outboards. Copying the best is a very useful strategy, as history notes.

The mounting bolt hole pattern standard is:

Top pair of holes are spaced 12-7/8" o.c.
The bottom pair of holes are spaced 9-7/8-inch o.c.
The spacing between the top and bottom pair of holes is 8" o.c.
The holes in the transom should be 1-7/8" below the top of the transom.

[seahorse]

Today's standard hole pattern for mounting large outboards was first used by Johnson and Evinrude for the 1960 75hp V-4 mounting brackets.


Now every outboard manufacturer uses the same bolt pattern.

[rbhankins001]

Ok, thanks guys!

I'm glad to hear that.

Now I just have to drop her off and get the F150 hung on the back!

Tight lines!