TOPIC: my first merc

hello i just recently acquired my first mercury 115hp the guy i got it from ran hot dont know how long but it was hot. i put new impeller in, exhaust seal, cleaned out rubber put together and started it. it sounds great but water is coming from areas it shouldn't. like around the plug area doesn't seem to be getting into cylinders is this repairable?

The Inline Six block has its cylinders integrally cast with the block. The cover you see at the back only covers the block's main water passage around the cylinder "jugs". The very ends of the block, where the spark plug holes are threaded, has a machined round flat pad that the cyl block cover seals against.

When the powerhead was overheated, the gasket became a "crispy critter" and thus the leaks.

New gaskets are avail and not extremely expensive. The tedious part of this job is pulling all the 1/4" bolts and not breaking them!

If the motor is a Salty Dog, you're probably gonna fight those bolts, and you don't want to break them, as it's not much fun extracting broken bolts out of an aluminum block.

If the bolts won't turn with normal force, don't use more. Instead apply heat in the form of a MAPP hand-held torch or equivalent. If you have a propane torch with a "rosebud" type head that has good Flamage, you might be able to get the bolts hot enough.

It also can help to give the bolt a good "rap" with a hammer & punch. This'll help shock any deposits loose.

If you have a fresh-water motor, the gasket R&R is a Piece of Cake!

Note that you'll be able to get more room to work if you remove the rear cowling brace/support. When you do this, you'll also be able to drop the back of the lower cowl somewhat, to gain more room to work on the lower bolts. It definitely is a job that can be done without having to pull the powerhead.

Once you get it all apart, scrape all the sealing surfaces, and if you get a gasket that has no shiny gasket glue on it, what I like to use is some Permatex No. 3 gasket dressing on the perimeter of the block & cover; and Red or equivalent RTV on the center "pads". Note, never use Permatex "Ultra Copper" on any aluminum outboard as the copper can set up a corrosion cell with the alum. That ain't cool!

Spread a thin coating of Permatex No. 3 on the bolt threads, they'll never get stuck again. The Permatex serves as a salt barrier to keep crud/deposits from building-up.

BTW, while gasket replacement is the proper fix for this problem, you can do a "quick and dirty" fix if you just need to run the motor for testing purposes without it leaking all over. Just leave the spark plugs in, clean out each plug hole with carb cleaner, and seal around each spark plug with RTV. Black would probably blend in the best and not look too ugly. Only a temp fix and of course if you pulled a spark plug, you'd have to do it over again.

Here's a good place to look up parts, just note your serial # and find the correct motor grouping:

www.marineengine.com/parts/mercury-outboard-parts/

BTW, congrats on your first motor being a classic Tower of Power, very awesome! Quite a wonderful engine to learn on, for sure!

HTH.................ed

p.s. any engine that has suffered an overheating carries the risk of piston scuffing and/or damaged rings. Probably a good idea to take a compression check before diving way deep into the engine and spending a ton of $$.

Mercury Master ed-mc wrote: "Note that you'll be able to get more room to work if you remove the rear cowling brace/support. When you do this, you'll also be able to drop the back of the lower cowl somewhat, to gain more room to work on the lower bolts"

AND,...If you also remove the 'U' shaped cowl under the engine pan (4) Phillips head self-tapping 'sheet metal screws", and remove the top (2) cap-screws from the top of the front cowl support (1/2" socket on 5/16" NC [course thread] cap-screws),...You will be able to get the engine pan down even more.
Depending on where the tell-tail water hose that comes from a fitting on the block is located, you might also need to disconnect it so that the engine pan can sag lower.
Be sure and either unplug the wiring harness or disconnect the battery while working on the beast.
I have learned a TON of Mercury Magic from my good friend and Mercury Guru, ed-mc.
He dah MAN
doc
Are we correct in assuming this 115 is an inline-6, or is it a 4 cyl 115??

Frankenmerc your duh man thanks for all the info!!! i think i can do this myself it's a freshy so I'm lucky there,your help will be a savings in my pocket. Hope I can call on you again when I get in a fix. Thanks much

ED MC thanks to you my money will stay in my pocket, you and Frankenmerc are great guys. Thanks loads

The Doc is Most Modest; he does some Awesome work.

Behold, just a smidgeon of the Masterpieces emerging from the Doc's skunk works: