TOPIC: Transom Bolt Patterns for 115 HP Mercury

I may be switching from a 1974 to 1988 115 HP Mercury and wonder how the bolt patterns compare on these two motors. The top two bolts seem about the same distance apart at 12-3/4, but the bottom ones seem to go from 7-3/4 to 9-3/4 going from 74' to 88'.

Can the top two holes be used on the newer motor? Can the bottom holes be plugged and new ones drilled about 1" away without weakening the transom?

What is the best way to plug holes?

Nice looking motor. I cannot answer that but I have a question.!! What years was oil injection used on the inline 6's? Was it standard or an option.
Conrad

The oil premixing system "Auto Blend" blend appearing around 1984 - 1985. It was standard equipment but many people by-pass or disconnect it because it can fail. There is supposed to be an audible sound if it does fail.

I have my used Auto Blend for sale on Craigslist for $75 and I see another ad there for a new unit for $130. To bypass it is easy, just connect the usual fuel line from the premixed gas tank to the connect on the engine.

Willing to sell mine if anyone wants it.

minneapolis.craigslist.org/ram/boa/2515227839.html

Thanks, I didnt know how they did it. Its a self contained unit in the boat cool.!
Conrad

That looks like something off a Info mercial .I thought it was like a True Oil injection .Theres nothing that moniters load or rpm and adds Oil accordingly ? Is it basically just mixing oil to gas at 50 to 1 all the time ?? On old 2 stroke bikes at idle they were at 100 to 1 or leaner and WOT at about 30 to 1 .Just Curious Not trying to be a Smart Butt ..

You asked some good questions. I do not know the answers to them, such as varying the ratio according to load or RPM. This was Mercury's first attempt,so I imagine they improved the system and refined it as the years went by.

I do not mind mixing as I use three six gallon gas tanks. The first three tanks are powdercoated, and the fourth was what they looked like before.

Nice looking motor! I have one too, and mine also came with the Autoblend.
I lucked out on this one. Paid $150 for it as the owner said he took it in for a tuneup and mechanic told him compression was low so needed rebuild not tuneup. Well it had a bad starter solenoid but all cylinders 135ish compression. THey also said the tilt/trim was bad. But the manual release valve was.....released. Tightened it and she tilts/trims like a champ. Fired up and runs great on hose.
Hoping for a load test underway either this weekend or next. Will post some pics soon.
I have a rebuilt powerhead with all new pistons 20 over for a 115 adi also, and going to look at an 87 Mariner 115 with bad powerhead. If I get that one will install the new powerhead. I like the look of the gray/orange Mariners with the tall tophat. Frankenmerc thinks I'm nutz he don't care for the tall tophat!

you should plug off and seal your old holes and re drill the old ones will not match. I think somewhere out there is a template for drilling the bolt pattern.

Darn AWESOME get on that motor sir.

To seal off those old mount holes, would you soak the inside of the hole and a piece of dowel rod of the appropriate diameter and length in epoxy resin, then drive it in the hole? Then you could perform the fiberglass (and gelcoat) repairs as explained in the research section? (Probably not "Merc Outpost" material, but since it's involving a possible transplant from one Merc to another......?)

dowel and sealer is fine.

Thanks guys. I'm getting the idea of how to tightly seal the old holes. A local Mercury dealer has a template to hang on the transom for the Mercury bolt pattern that I may use/rent when that time comes.

Can you send me the SN for your motr?
Thanks, I'm looking for lower unti parts for this vintage and need an SN to do so.
Thanks,
Randy

Randy,

Send me an e-mail of the parts you need. I may have a source!

Jim Savage
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The S/N of the 1988 115 HP is OB260433