years on johnson gt 200s

[Instigator]

more go than a 235....
that could of had a 235 propshaft rating....
I know OMC in OZ thought about marketing as such.

I had one.
I know when I re powered w/a new in the box, '89 GT 200 I picked up 3 mph.
Same, boat, prop, height etc and the GT was one of the 90 PSI motors.

[sharpeye Mike]

Just curious, how fast could they be spun?

[Instigator]

Just curious, how fast could they be spun?

Hard as you can get them to spin.

[action1923]

So was it a markerting move or did the GT have more Hp or differnt drive ratio? Also what was a GT rated at? I anyone know?

Outboard manufacturers are allowed to produce +/- 10% hp versus the "rated" hp or decal hp of any engine. The Johnson GT's, Evinrude XP's and HO's, Mercury Pro XS's and Yamaha SHO's typically develop +10%. These models also typically feature other performance enhancements such as stiffer mounts, bigger carbs, different maps, alternative gearcases and ratios, etc. The Johnson 200 GT's did feature larger carbs, stiffer mounts, louvers in the cowling and produced about 220 propshaft hp. Tighter heads and some carb jetting got them into the 250+hp range. 6700 RPM rev limiters were easily defeated and most of the serious hotrodders turned them north of 7000 RPM.

[Instigator]

The Johnson 200 GT's did feature larger carbs,

Only the 2.7 liter, '86/'87's.
The others were all 225's.

They only made three sizes of carbs for the V-6 loopers.

Big Bores (approx. 1 5/8") '86/'87 only.

Mid bores (approx. 1 1/2"), which were the 225/XP/GT carbs for the rest of time, after the 2.7's.

Small bores (approx. 1 3/8"), which were the 200's from '88 and up.

They changed designs several times, as in adjustable idle jets etc.

As to porting, I've been into quite a few and have never seen any differences/improvements in the GT/XP's.

I've been a JohnRude guy all my life and to me, the GT/XP thing, other than the early days, has always been purely marketing.

The strongest carb'd V-6 they every built was the 225 HO/250 Ocean Pro's (same powerheads) that came out in '98. I've owned and been through a half dozen of those and loved them including two, new in the box.
Their exhaust ports were approx. 1/4" (as I recall) wider than a stock 225 but same height. They also had smaller exhaust bleed ports which raised compression approx. 10 psi. They did have the same heads and carbs as the 225's though.
They were rated at 254 HP's at the crank and 247 at the prop. So there's our +10%.

They were a dead heat, or a bit stronger than a Merc 225 Pro Max. I built one for a customer and broke it in on my old STV.
I bumped into a friend w/a Pro Max on his Mirage and we raced each other a dozen times in about 5 mins!
From idle, roll etc, etc.
I won all but a couple.

IMO, the 2.7 debacle scared OMC from ever doing anything hot rod again.
W/the big bores, they were WAY over carbureted for a heavy boat. Then if you ended up w/a XP/GT, the heads were cut .025", air box restrictor was deleted so it made it even worse.'86 XP/GT's had same carbs as 225's.

I have friends that worked in the dealers of the day and they tell stories of OMC retrofitting all the big bores w/mid bores with conservative jetting.
Tales of dumpsters full of big bore carbs.
OMC's answer was the 3.0 liter in '88 instead of realizing what they had.
IMO, an '86/87 GT/XP on an Action of the day, set up properly would have been hard to get around.

On a center console though, not so much.

On the '98 and up HO's, I don't think the dealers did a very good job w/these. The changes truly brought these motors to life but they (dealers and owners) treated them like the stock, 100 psi cousins and they weren't. Over prop run on **** gas and your done.
Explains why there are very, very few of them left existence.
I looked at several that actually had stock 200/225 replacement p.heads.

I bought a pair down there, from a large dealer, represented as virgins off a repower. Part of the deal was a compression check.
My schedule didn't allow me to be there while they did it so I trusted the dealer.
When I got there to pick them up he handed me a sheet showing all twelve holes at 100 PSI. Soon as I saw that sheet I knew either they replacement p.heads or the dealer never did the compression test and was lying.
Based on visuals, I guessed on the latter and loaded them up.
When I got home I did a compression test (to see if I got Fk'd)while they were still in the bed of my truck!
All 12 holes were 110 - 115 which proved them to be HO/250's.

In other words, the dealer (that sold them new) didn't even know what he had.

[racer]

Only the 86 200XP/225 came with big bores the 87 had mid's, small bore's were on 25 inch shaft length 200's. 86/7 300xp had big bores