Diff between 45, 55, 65, 70hp???

[1972Playmate]

I have a 1986 Mercury Classic Fifty (4cyl 45hp) I was wondering if someone can tell me what the diffs are between my power head and the 50, 60, 70hp 4cyl I have been cruising the diff parts supplier websites and it looks like pistons pins rings and bore sizes are the same even carbs where is the extra power coming from? is there a diff in stroke or what? will the 65-70hp crank fit in 45hp powerhead? do all these parts really interchange? or am I missing something? if that is the case how much potential power can be squeezed from the 45hp engine? Thanks

 

[Fuzzytbay]

Re: Diff between 45, 55, 65, 70hp???

About 45 hp.

 

[CharlieB]

Re: Diff between 45, 55, 65, 70hp???

Check those parts catalog long enough you'll .....................


You should find a difference in carb #'s

Once you see the price for a complete SET of larger carb's you should feel a WHOLE lot better about keeping your 45 bone stock.

 

[1972Playmate]

Re: Diff between 45, 55, 65, 70hp???

Hey guys thanks for your input about the carbs and and concern for my wallet but these engines are getting old enough that used parts can be had for reasonable money I was wanting to know more about the powerheads are these 4cyls all the same internals with different carbs? diff head? or is it more than that? and yes I understand hp and going fast can be pricey but I dont leave anything bone stock how much of a diff do you get w/ boysen reeds? are they worth the $$? this outboard is going on a 11' 2 seater boat I want to get as much as I can out of it

 

[1972Playmate]

Re: Diff between 45, 55, 65, 70hp???

By the way if anyone has another "smart" answer like Fuzz.... save it ok thats not what Im here for!!!

 

[Fuzzytbay]

Re: Diff between 45, 55, 65, 70hp???

If it was a simple as putting on new carbs, who would buy a larger HP motor. We all would simply buy the smallest HP motor we could, and get bigger carbs.
While I am not 100% sure, I'm guessing the exhaust ports are different, ie larger, and the shape, The crank would be different. I suspect the reeds would need to be changed and a new intake manifold.
Simply pouring in more fuel (bigger carbs) may slightly increase HP output, but its actuall running performence, would not be spectacular. You would be better off getting a large powerhead, and bolting it on your leg. Although thats not really what you after I guess. So now I've added all this, to answer your question......."about 45 HP"

 

[Faztbullet]

Re: Diff between 45, 55, 65, 70hp???

Your classic motor is the same design as the 1970-84 50hp,1986-89 45hp and the 1990-97 40 hp as all are 4 cylinder 2.565 bore. The the 1985-90 50 & 60hp are a 3 cylinder as are the 1973-7665 and 1977-83 70hp. The 3 cylinders are bigger bore engines (2.875) and a bigger carb will not increase hp on these engines much as the reed blocks can only flow so many cfm's. Also 90% of the 3 cylinder parts will not fit a 4 cylinder

 

[1972Playmate]

Re: Diff between 45, 55, 65, 70hp???

Thanks Fazt you got a 13 footer w/ 150hp on it! my kinda guy! ok will the larger hp power heads bolt to the classic leg? how much diff is there in weight from the 45hp 4cyl to say a 65 or 70hp? are the 3cyl engines lighter? just tryin to go lil faster on a budget are there small less than 80hp Merc outboards that can be modded easier or cheaper than others?

 

[Faztbullet]

Re: Diff between 45, 55, 65, 70hp???

The motor below is what you need, with a little port work, head shave, use 1980 model carbs and intake and if you can find one to make a ultimate ride a Mod 50 intake that uses 3 of the V-4 2barrel carbs!!!! UMMMM MORE POWER!!!
Yea the 13 is my toy and slick water use only, best run is 73mph @6100rpm
its covered in dust in barn and hasnt seen water this year due to being so busy.
http://cgi.ebay.com/ebaymotors/1976...4629780QQptZBoatQ5fPartsQ5fAccessoriesQ5fGear