Okay, as a owner of a converted 170B, I'll stick my neck out boast about the engine upgrade, . . . and wait for the tomatoes to fly.
I have a 180 hp 170B, but I bought it that way in May of 1997. So I benefited from somebody else's investment. My plane was a true bush plane -- light, automobile parts, paint falling off, etc.... and an amazing performer.
During the past 6 years, I have put a lot of money into the plane, including an overhaul of the engine, new prop, paint, sportsman stol, etc... I now have it just the way I want it (except for the wiplines I want to trade up to from the Edo 2000 when I hit the lottery). But the paint, sportsman, longer blades, and fancy strobes added some significant weight. It still out-performs most stock 180s when fully loaded.
Here's my (very biased) opinion on the comparison between the 170B, the converted 170B, and the 180:
1) the stock 170B is underpowered on floats. If you're a big guy, pack a light lunch, but not much else. (just kidding, you can get more in, but not a lot). Ski performance is o.k. with Landis 2500s, but wheel skis or penetration skis are too heavy and have too much drag in heavy or deep snow.
2) the 180 hp 170B can get off of the water with full wing tanks PLUS over 1000 pounds. If it'll float, it'll fly. I think this is true with either the Edo 2000s, PK 2300s, or Wip 2100s. On floats with the Lyc., you'll get 4 hours of fllight at 24 squared, running at about 105-110 mph with full wing tanks and heavily loaded. If you have fuel in the javelin, your weight will be limited ON FLOATS, due to a lack of floatation in the back. Even though you have a heavier engine, the Edo 2000s are slightly under floated in the back, thus requiring you to load forward. In the summer, on wheels, fly with the javelin full, or put your survival gear in the extended baggage area and she'll fly better.
3) With the Franklin, you have the option of running Edo 2440s and hauling even bigger loads. The fuel burn is at least 1 gal/hr more than the lyc., and possibly 2 gal/hr more. This is an AMAZING performer. I know of no Cessna 180 (except for a buddy that has the 300 hp conversion)

that can out perform the Franklin powered plane. And it flies considerably faster than the 170B with the 180 hp conversion.
3) To get the same range with the Cessan 180, you need a lot more fuel. And with the bigger floats and heavier plane, it just won't carry the same loads as the Franklin. I have seen some 180s that carry the same loads as the lyc 170B, others that were dogs and couldn't come close, and some that can carry more. I don't know enough about the different types of Cessna 180s to explain why this is, but I've noticed a HUGE difference between their performances. This summer, for instance, a buddy's 180 tried to get off of the water 3 times, without success, with a load LIGHTER than mine and unlimited water to work with! I got off, first try! Even though he flew faster, he still arrived at the destination after me. It must have had something to do with the multiple stops in-between take-offs to unload a little gear and burn a little more fuel. With full tanks, that 180 was a dog.
4) And how 'bout them expensive annuals. It sounds like the annuals on 180s are more expensive. Perhaps that's just an incorrect rumor.
In Alaska, where float and ski operations are much more common, a conversion (any of the conversions), is the way to go. I have the Fli-Lite 3000 wheel skis and have been able to fly all winter (during our Seattle-like winter we've been having). With the stock plane, the weight and drag of the wheel skis in the snow would seriously limit the usefullness of the plane. The speed isn't a factor for me -- I'll get there when I get there. It's the ability to take what I need and get off the water (frozen or wet) that matters.
SJ, you're plane will still look beautiful, even with the bubbles on the cowling. I appreciate, and respect, the members' dedication to the original 170, 170A and 170B. But if you are comparing the converted 170B and with the 180, I think there's no comparison -- the converted 170B is a MUCH better plane. Not to mention the view, easy of handling, etc................ of the 170B.
BUT, perhaps the conversion is not as useful in the Lower 48.
Okay, let the tomatoes fly
-Rob Stone
N2814C
Anchorage, Ak