JohnnyRude question

[chumbucket]

Skools, Ferm, any other JohnnyRude gurus;
On the 3 cylinder 50/60/70 hp motors, they are all essentially the same. Right? What are the differences that make up the horsepower variables? Is it all carbs? Are the reeds different? I'm almost sure that the bore and stroke are the same on these motors, but could be wrong. I really don't know.
Please enlighten me.

[THEFERMANATOR]

I know that there were some different ignition systems used on them early on(non magneto styles). I'm not really up on the old loopers myself, only the 90 degree engines. But OMC was famous for making only small changes to each engine and keeping the block and such the same across the board. Normally the tuners were different as well as carburation. Some years had different reeds as well. MERCURY was the one that made it complicated, they would make 6 different variations of a block and they would all be the same HP rating. You can always go here http://12.2.215.22/pub/default.asp?S...g=EN&brands=EJ and look up the different part numbers for each engine to see what changed.

[chumbucket]

Thanks Ferm. That catalog looks like it'll take a while to sift through. I was hoping for some quick easy answers. I'll peruse the differences in that catalog late tonight when there are fewer disturbances in the house.

[chumbucket]

I guess what I'm wondering is; how difficult would it be to say, turn a 50 hp 3 cylinder into a 70 hp 3 cylinder. Can I just change the carbs and get the extra hp out of the motor? I'm looking at a bigger motor, but was wondering if I could save myself some dough and do the simple upgrade.

[THEFERMANATOR]

What year is it?

[chumbucket]

1997

[THEFERMANATOR]

Here goes, according to the catalog the 50 uses it's own unique cylinder head and the 60 and 70 use the same head. The carbs are different for a 50, 60 or 70(figured this was the main difference), but the rest of the parts look to be the same. Even the exhaust tuner is the same part number for all 3. So if you have a 50 you'll need a 60/70 cylinder head and the bigger carbs with the correct jets for the bigger carbs. And possibly a different timing setting. So if you could find a cheap junk 70, you could swap a 50 to a 70 in a few hours time.

[macojoe]

Hes to lazy for that!!

[chumbucket]

I'm too lazy? I'M TOO LAZY???????????? HA! Go back to sleep.

Ferm. Thank you very much. Do you happen to know what is unique on the 50 cylinder head?
You touched on why I'm asking this. The new ProLine boat I boat has a 50. Underpowered for sure. I know where I can get a junk 70 with a good power head for $500-$600 complete.
I also have looked at a nice 1998 90 hp Johnny which, if it runs as good as it looks, I can get for @ $1800-$2000.
I'm leaning towards the 90 if it checks out. That is the top end of what the boat is rated for. There were a couple of other four stroke motors I looked into, but the extra weight/power ratio didn't seem like a good match for this boat.
What ya think?
MJ. Step away from the keyboard and go back to sleep.

[THEFERMANATOR]

It probably has a more closed design on the 50 cylinder head to lilit the flow through the cylinder. As for the 90, do you know if it is a looper or cross-flow. Both were available in 98. If it's a looper I would consider it, but a cross-flow is one thirsty SOB. Upgrading your 50 to a 70 would probably be the cheapest, and then get a good prop. I had a friend with the same PRO-LINE that you have and his had an 85 MERC on it, he felt it was slightly overpowered for him.