Mercruiser...Do I plug the Hole?

[Islandtrader]

I am in the process of taking out the old wood in the transom. The boat had an R Series outdrive. If I was to put in a Bravo 2 drive would the "big hole" be the same?

When I was looking at it today, I thought if I don't have to fill in the hole, all the better.

[bigeasy1]

Island,
I would cover the hole.I have the Mercruiser cutout pattern for all the Mercruiser drives,and would gladly make a copy and send it to you.
It's a full size paper pattern,and gives you all the bolt placement markings,along with the driveshaft centerline markings for the placement of the pattern.It also gives you all the X dimensions and transom angle measurements.It covers all the alpha and bravo drives.

I replaced the transom in my Tsunami I/O recently,and did it from the inside.I used marine plywood,and bedded it to the outer skin, and covered the hole.I did lay up two layers of 1708 to the face of the outer skin,to beef it up a bit before i put the core in.

After it cured,i glassed over the new plywood on the inside with a few layers of 1708 and tabbed it all into the hull. inside.
Remember,the transom thickness has to be between 2 to 2-1/8" according to mercruiser specs.

Here's a few pics of the old and new transom and old and new engine beds.

*******If you want that pattern just send me a message,and i'll get it out to you.******

The pics are
#1- original transom and engine beds
#2- fabricating the new transom
#3- installing the new transom
#4- laying up layers of 1708 on inside
#5- finished glass work
#6- done and gelcoated

[Islandtrader]

John, good thing I asked. See my picture below. I think it was a conversion from OMC to Mercury. I will PM you with my address.

Round Hole...

[bigeasy1]

Wow,
I've seen lots of cutouts for outdrives,but never one like that.The tsunami i'm doing is a 74 and i removed the original drive,which was a Mercruiser MR type.The cutout on it was almost the same as the newer type Alpha's and Bravos.

I also have a 22'Trophy with a OMC cobra drive and that cutout is similar to the merc.
Did you remove a drive that was in the boat?,or did you get it the way it is in your pictures?

I'll get a copy of the pattern,along with some Mercruiser installation literature,and send it out to you.Get some extra copies made for yourself, so you can play around with them,when you're ready to make the cutout.You'll need them as they're only paper.

You'll have to get them done at Staples,or some copy place,because it's a pretty large pattern,and a regular copier won't do it.They're only around fifty cents a copy at Staples.

Also i think you'll want a Bravo I or Bravo III .The Bravo II is made to push big heavy loads more suited to slower craft.It's not the best choice for your Seacraft.I learned this from lots of research when i was deciding on what to put in mine.

[Islandtrader]

I pulled out the drive, check out the photo album, and you will see what I have. I am sure it is an r series, but I do not know what all the other stuff was.

Out drive parts

I was thinking Mercruiser duo prop drive? Does that make sense...

[bigeasy1]

It may have had a transmission on it.Another guy on the site is doing a scepter I/O over that had an outdrive with a transmission,his username is Ebeach,he may be able to give you some info.
The duo prop is a Bravo III. Volvo also has a dual prop,and i beleive they are the ones who coined the name Duo prop for their drive.

[nestorpr]

That looks like a cutout for an old OMC drive or a very old Mercruiser, plug it and cut a new one for the new drive.

[Islandtrader]

Thats the plan. Now that I know it makes no sense to leave it.

This site is great, ask a question and most of time get answers that help you make the proper decision.

Thanks everyone.

[Islandtrader]

This old picture of the 21 sheds some light on why the hole was so big.

Picture compliments,of bushwacker.