1991 Gt 200

[stratos976]

Hi everyone, I'm new here, if this is the wrong place to post this let me know.

I've got a 1991 Johnson GT200 m/n VJ200SLEID s/n 02600222. I just wanted a little history on the GT motors pros/cons, and some things i can do to get the most out of it, bolt-ons tweaks & tuning tips.

I'm just a bass boat guy, but would still like all the performance I can. Currently this motor is hanging on a '91 Stratos 201 pro, running a 24p raker @ 5800r's, 60mph. Right now the motor is too high on the transom, Im in the process of putting on a 6" plate.

Thanks,

Andy

[BenKeith]

Motor has bunches of potential, just a matter of how much you want to spend and finding someone that knows how to do the work.

I built 94 200 for a friend a few years ago that's pushing his 94 201, 79.3 mph with two men weighing over 220 pounds, and was actually gps'ing 81 @1,200 degree egt temps but I went up one jet size for a little cushion and that slowed it down to 79.3. I installed an 8" jackplate on friends 94 201. It's turning a custom tuned 28" raker approx 6,400 rpm.


The problem is trying to do it yourself usually cost you a motor, or two. I started off thinking I knew a lot about outboard motors and went through several blocks and bunches of pistons before I found out I only thought I knew something when I first started modifying these loopers.

The standard do it yourself mods are installing 225 carbs if it doesn't already have them. Plugging the relief ports to boost the compression and throwing the heads on that motor in the trash and finding a set of good heads. The good heads are going to be Stoker's 48cc offset chamber heads (probably the best), getting a set of 93/later heads and having them cut to 50CC or finding a set of early 2.7 225 heads that someone hasn't already butchered. Any of these heads with plugged reliefs will give you pretty close to 150 pounds of compression so you must run 91/93 octane but will make a big difference in hole shot and midrange punch.

Glass reeds are not going to do anything for more power, gutting the air box usually won't help much on a 5,800 rpm motor but is a popular thing people do. Just don't run without an airbox or with a gutted airbox without going a whole lot larger on the main jets, it will melt a piston.

The thing is, the big gains will have to come from tearing the motor down and doing a lot of cleanup and porting to the block.

[stratos976]

Thanks for the reply!I assume my motor is a 3.0L? I just found a series on Bass & Walleye boats website called "budget basser", they are working on a Bullett w/ a '92 GT 200, it's got me all worked up about tweakin' on mine... especially the EFI that may become available:thumbsup:..

If I found a set of the 2.7L heads or got the Stoker 48cc ones, is it typical to have to do a jetting change??

Also related to jetting out of curiosity why do the portside carbs have a #55 and #33 air jets while the starboard has #55 and #31's, this seems to be correct according to the breakdown in the manual, just wondering

[BenKeith]

I've never been into a 91 but I think that's the year they went to the tea cup intakes, if so, they will need to go and be replaced with the earlier or later (96 or later). Maybe someone else can say for sure. If I was going to do anything, I would start off with a set of 96 or later 225 carbs and intakes. You can use you're airbox but I would take the baffle out. If you use the late model air box you will need the bracket that holds the throttle and shift cable off a late model motor.

You have to be very careful when buying 2.7 heads. The 200 hp 2.7 heads came from the factory shaved .025". You need the 225 heads and the chambers will measure 1.70 inches deep, 200 heads will only measure 1.675". Then you have so many floating around that people have shaved even more. This is not a major problem if you don't plan to plug the exhaust reliefs but any of the shaved heads will give you too much compression if you do plan to plug them.

The offset chamber heads will give you more hp than the 2.7 heads, just how much will depend on what all you do to the motor but I think 7 - 15 hp is not out of the possibilities.

ANY CHANGES to your motor will require rejeting.

Two different EFI systems are already available, just plan on spending close to four grand on it by the time you get running with it.

[jphii]

If you're going to use stock intakes I like the later ones better.

[roadkill636]

[quote=BenKeith;161569 the 225 heads and the chambers will measure 1.70 inches deep, 200 heads will only measure 1.675". .[/quote]:confused:


If you find some heads with these measurements,,, someone must have welded on a 1" spacer to them to get arround 3-5 pounds of compression!!!:eek::eek::eek::eek::eek::eek::eek::eek::eek::rolleyes::rolleyes::rolleyes::rolleyes:: rolleyes::rolleyes::rolleyes:

.675" .700" :thumbsup:

[BenKeith]

OOOPPPs, never could type, spelling is just a bad as my numbers. Keep me straight.

[baja200merk]

You have to be very careful when buying 2.7 heads. The 200 hp 2.7 heads came from the factory shaved .025". You need the 225 heads and the chambers will measure 1.70 inches deep, 200 heads will only measure 1.675". Then you have so many floating around that people have shaved even more. This is not a major problem if you don't plan to plug the exhaust reliefs but any of the shaved heads will give you too much compression if you do plan to plug them.


i had 3 different sets of 490 heads on mine and never saw 140lbs :confused: i think it might be the napa compression gauges but i dono, wish i had that much with stock 2.7s :(.. i was recently informed that the casting number doesnt necessarily = chamber depth

[roadkill636]

I have the 408 heads and they are .675" deep 114-118 psi

[BenKeith]

Plugging the relief holes in each cylinder and running the stock exhaust port height on a open deck block, the .700 heads will give very close to 150 psi on a good motor that was warmed before checking. Not sure what they will give on a motor without the relief holes plugged because I've never run one. That's why I said if he was not going to plug the relief holes, the .675 (got it right that time) or even a less would work fine, but will give too much compression if he ever plans to plug the reliefs.

[David]

Conventional wisdom is to start with set up, set back, engine height, props, before opening up the engine for modifications.

[stratos976]

Drug this back up... Ended up havin to replace my L/U right after I posted this last year...Got that all broken in, and J.P. installed..much better on lift. I've settled right around 3.5" below pad...now running 65 @ 5800 R's w/ a 25" renegade.... never did any work to motor last year.

This year I need to replace the Reeds...pretty sure their original....looking for suggestions on which ones to go with....I'm a tournament guy so overall performance is important....also what jetting changes are typical, for a upgrade in Reeds?

As far as plugging the reliefs for each cylinder, how involved is that process? Would I have to pull the heads to do this?

Sorry for some of the possibly dumb questions but I'm trying to learn what I can....

[phil blomquist]

reeds being tested on here soon by eagle 1 and also by racer so i would wait for the results of that before i bought mine the idle relief plugging was just recently talked about check a couple pages back some differant ways of doing that . jet size is should be up 2 sizes for fiber reeds as a rule of thumb