Mercury 85hp vs 80hp?

100333624

Petty Officer 1st Class
Joined
Apr 24, 2012
Messages
205
Ok bare with me in this post, I have to tell you guys this short story!

So what a birthday its been today! Ok so 2 nights ago I said a prayer (yes I believe in Almighty God!) due to my extreme financial situation (car accident/surgery/job loss) my insurance has been treating me, ummmm, the way they treat most of their clients.. And so I said a prayer asking for some financial support in terms of my situation, and what an answer I received!!! Later on the next day I found out that my insurance is going to FINALLY send me some money, and then that same night (late last night) I was going through the ads on my local kijiji.ca and found a guy selling a 1976 Mercury 85hp 4cyl for guess how much? $150!!!!! Maybe that doesn't sound that great to you, but WHAT a blessing to me!!!! The Almighty sure knows how to amaze me, and this is the second time He's done this to me, both times answering my prayer the next day, AMEN!

Now onto my post,

So now that I'm the proud owner of a Merc 85hp, I have some questions for y'all, and for those who don't know, I have a 1978 Mercury 80hp 4 cyl model, and I had to remove the powerhead and the exhaust extension plates due to a rusted and broken swivel pin assembly shaft, and bottom yoke.. I asked my local dealer to find me these used parts so I can replace them, along with the lower exhaust extension plate which I had drilled through to remove the piece because the bolts had rusted and seized in there and it got butchered. So he said he'd find me those pieces and it'll be $200 all together. Then I found the 85hp and figured why not get the whole motor and use it for parts since it's compatible with mine and for only $150?

So here's the idea:

The motor looks clean and good, especially the mid and lower units.. Instead of putting my 80hp back together, I'd rather use this 85hp mid/lower because its in better condition than my 80hp, but I think I'm gonna put my 80hp powerhead on it instead. I might keep the 85hp on it if it runs good, the man said it has good compression and spark, but hes never ran it as he picked it up to swap some parts from an old 80hp he had, mainly cowlings and whatnot.

I will test it out to see if she runs, and if she does then that's great, but if she doesn't then I'm gonna throw my 80hp block on it. Now here's the real question: What is the difference between this 85 and my 80? How did they get 5 more hp out of this? Was it the carbs? As far as I can tell the motors looks exactly the same and my 80, except for the powertrim/swivel bracket assembly units, but the 85hp parts fit my 80hp motor as they are the same parts... So what is the difference? If I use my 80hp powerhead with the 85hp carbs, will it then produce that 5 more hp? I would rather just use my 80 powerhead because she was running fantastic and I trust it!

I apologize for such a long post, any help from you guys is ALWAYS appreciated, you guys ROCK! :happy:


Nick
 

downintime

Seaman Apprentice
Joined
Jan 30, 2013
Messages
35
Re: Mercury 85hp vs 80hp?

I cant say exactly what makes the 5 more hp but it might have to do with the porting, the carbs or timing.
 

100333624

Petty Officer 1st Class
Joined
Apr 24, 2012
Messages
205
Re: Mercury 85hp vs 80hp?

I cant say exactly what makes the 5 more hp but it might have to do with the porting, the carbs or timing.

It sucks that usually I get a lot of good responses in my posts, but this one only one response.. Oh well I had to do a bit of research and all I can figure out is like you said, the porting and pistons are different on the 850. It seems that I could use the 850 crank assembly (pistons, rods and crankshaft) on the 800 but cant use the 800 pistons on the 850 as the 850s block is ported differently to make for the difference in the 850 pistons.

Anyway, I almost got the 850 going, I just had to check the lower unit and was fooling around with it all day. Will work on it monday to get it started.. If it starts it will be awesome because the parts on this motor are in VERY good condition. I can imagine it must have very little use in its life, not to mention I'd have 5 more hp on a boat that's already doing close to 40mph with 100lbs of water weight and broken structure underneath. Just imagine how quick it'll go with a new floor and structure plus prop tweaking!!
 

downintime

Seaman Apprentice
Joined
Jan 30, 2013
Messages
35
Re: Mercury 85hp vs 80hp?

Sorry you have not gotten any better or more specific info. I have a post that has gotten no replies either. Anyway, i have a 1974 85hp 4 cyl that i am looking to part with so if your interested in parts or the whole powerhead we can make a deal on it. It is complete and ran until i parted it out cause of a trashed lower unit. I picked up several towers of power so this motor is no longer needed. It has the "direct charge 4" which is mercs fancy term for the extra porting done to it.
 

100333624

Petty Officer 1st Class
Joined
Apr 24, 2012
Messages
205
Re: Mercury 85hp vs 80hp?

Sorry you have not gotten any better or more specific info. I have a post that has gotten no replies either. Anyway, i have a 1974 85hp 4 cyl that i am looking to part with so if your interested in parts or the whole powerhead we can make a deal on it. It is complete and ran until i parted it out cause of a trashed lower unit. I picked up several towers of power so this motor is no longer needed. It has the "direct charge 4" which is mercs fancy term for the extra porting done to it.

You got PM
 
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