82 70hp specs

younggun

Petty Officer 1st Class
Joined
Jul 13, 2012
Messages
251
I am considering purchasing an 82 model 3cyl 70 that I can get rather cheap. I have been searching high and low and coming up empty but I was wondering what the lower unit gear ratio is(I know it's a 3-1/4" diameter), and also what the power head displacement on it is. Anyone here have any experience with these? The light weight interests me. Any help on this would greatly appreciated!
 

Alumarine

Captain
Joined
Feb 22, 2005
Messages
3,684
Those are 49.8 ci or 816cc's
Ratio is 1.64:1 or 1.83:1 depending on serial number.
 

jimmbo

Supreme Mariner
Joined
May 24, 2004
Messages
12,944
A 1982 70 hp would have a 1:83 ratio
The 70 is basically half of a 140hp inline 6. On the exhaust side the 140 was two 3 cylinder engines. On the intake side it was three 2 cylinder engines(2cylinders sharing a carb). The 70 is kind of a weird duck as it 3 cylinders sharing 2 carbs, or it had 2 cylinders fed by one carb and one cylinder fed by it own carb. It made for some interesting jetting.
OMCs 49.7 inch 55/60/65/70/75hp engines used one carb per cylinder
Mercury used to boast about their 3 cylinder being lighter than OMCs.
 
Last edited:

younggun

Petty Officer 1st Class
Joined
Jul 13, 2012
Messages
251
Thanks for the help! Are they crossflow engines? Thinking about picking it up for something to tinker with and put on a little river boat since it's so light for the size
 

tommarvin

Ensign
Joined
Nov 22, 2015
Messages
999
Im not trying to be down beat here, but if your boating budget is enough get a used/new four stroke EFI.
 

jimmbo

Supreme Mariner
Joined
May 24, 2004
Messages
12,944
They were a variation of the crossflow design. Mercury called it direct charge, it also had what mercury called 'power ported pistons', an added transfer passage using a hole in the piston skirt and a channel/dimple/carving in the cylinder wall
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
36,033
The # 2 cylinder pulls air in through the top reed block from the top carburetor.---Pulls the other half of the air throug bottom reed block from the bottom carburetor.-----Inspect around the top sparkplug as top cylinder dome is known to crack.-----Compression test before handing over the coins.-----Replace impeller and look at poppit valve if equipped with one !.
 

younggun

Petty Officer 1st Class
Joined
Jul 13, 2012
Messages
251
Thanks for all the help! I play with 3cyl engines in my spare time and see what I can get out of them. Will probably be torn down eventually anyway and rebuilt/built. Guy has this motor, 2001 75 mercury with low compression in one and a 71 60johnson(electric shift but buddy wants the powerhead for a spare for his old stinger) and a set of mercury controls and set of Johnson controls. I can get it all for 500. The 82 will be the oldest motor I've ever messed with and wanted to try something with a crossflow motor. I like doing things and making a 3 cylinder that's not the typical ones you see being built as fast as I can and surprising some people

To the get a newer EFI/ 4 stroke comment, that's what's on my bay boat. This will be a play motor on the back of a light boat
 
Top