TOPIC: Oddball 650 3 cyl

I'd like some opinions on this thing please.
Pulled apart a 1979 Merc 650 3 cyl or maybe it's a 70. I know " why bother" but the customer wants Max hp & minimum weight. So we're going to build something like a 650XS to go on an 10' 1967 GW invader.
When I got inside the reeds are like nothing I've ever seen before.The first thing I noticed is that they're designed like the older cages like in the 89 & 44 cid motors instead of the type that are in the 99 cid.motors. The 99 cid cages will fit right in this thing. What I'm wondering is would I be better served to use thewse cages or go to a set out of say a 1500. We're looking to get max performance out of this thing. In fact performance is a higher priority that durability.
Tim

A 79 ??

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That would be a 70 HP model.

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The more air you can flow into these motors the more performance you get.

Thanks Prof. After a little investigation I guess this is as good as it gets for these. I do sometimes tend to leap before I look.

Yeah, 70hp was about the max out of those 49 cubes. Really not bad considering it was basically half of the I6, which produced 140 at that time...

Chinewalker wrote:

Yeah, 70hp was about the max out of those 49 cubes. Really not bad considering it was basically half of the I6, which produced 140 at that time...

You must be forgetting the 90hp 1976 650XS.

I've heard about those 650XSs would really like to see one & figure out what they did to get all that extra HP.

The 650XS was an odd duck and was only produced in limited quantities. VERY different from the stock 650... Of the few racers I've known who actually ran the 650XS, I don't think any of them had good things to say about them. The Johnrude triples were a much better motor in those realms...

Or,...You could always track down a 700x triple that - like the 650xs, came with pyrmid reeds and 3 big carburetors.
It is my understanding that some of them were not class legal due to the limited number produced, but I defer to Chinewalker on the racing specs.
Also - as CW says,...The OMC triple can be built to walk away from Mercs' attempts in this category.
I can snag a 700x block & crankshaft (1-2-3) hot-rod fitted with a rope start flywheel disk, cdi trigger, .015 cylinders (no original 700x pistons), but 1350 pistons work fine - no power port used.
It has the original 700x crankcase cover fitted with 14 pedal reeds (two sets of 7 pedal per cyl) & three early T2 carburetors (the rectangular ones).
It is set up with a dry stack filler block, but would probably be wise to find the parts needed to go back to quiet exhaust.
It is not an original 700x and would be considered a hot-rod collection of various Mercury Racing parts, etc. No DSH, etc., Just a dis-assembled pile as listed.
I 'think' $500 would buy it.
Thom

The 650XS was basiclly half a twister on a stock midsection/lower, Sold through the dealer network to you and me, 76 only. The 700 was a race motor/mid/lower sold through Merc Hi-perf.
Potentaial H.P. wise, OMC loop charging is superior to the direct charge design of the Merc which really is only a tweaked cross flow design. The 650XS/700 and the OMC all used front reed cages. The wrap around the crank cages of the stock 650 Merc as used on all the inlines is not very elegant from a max flow point of view and not much can be done for noticable h.p. improvement. Merc went to front reeds on the race in-lines for noticable h.p. increase coupled with very different exhaust tuning and flow to and through and out the mid section.
This in no way should indicate I don't like my in-lines! But no doubt OMC had a better basic design answer in that displacement size than Merc did at that time.
Take those Merc 650 cowls and wrap them on a 70 Johnrude to mess with everyones head Boy, the guys over at the G-3 site would go crazy over that!
Randy

Here's a crazy thought:

How 'bout a fully-loop-charged, six-cylinder Tower of Power!

Get out your chop saw, welder, some Phantom Black paint then stand back and watch 'er roar!!!!