Diff in Johnson 150 and GT150

I just bought a nice lil 17'10" Charger bassboat..the boat and motor are both 91 Models...what is the diff between the GT150 and reg 150? Mine has the GT model on it...Im having to take it moday to get teh steering cable changed out, but other that that it a great lil boat..I took the cables out of the slides ni back, and motor will free turn...so its in the cable somewhere, and I could not find a part # on cable, or I would probably order them and change them myself....I have erad ALOT of great info on this forum, so I decided to join...TY in advance for any info on GT engines...btw...it was just totally rebuilt less than a year ago by a local big dealer here,,,so Im sure its gonna last me for a while

Thanks
Jimmy

Re: Diff in Johnson 150 and GT150

The GT/XP engines from OMC have an "S" in the engine model code, such as: 150S. Check for this to be sure someone did not just put the special cowling on a straight 150. This "S" means that the engine is a special model with 175 carbs. The engine will putout 10% more hp than indicated on the cowling, or about 165 hp. They usually have stiffer lower engine mounts for better high speed steering, cowling vents and special decals. These engines are a sought after model.

Re: Diff in Johnson 150 and GT150

And they have different heads, pretty good ones at that. Some had the port timing at or near that of the 200 crossflow.

Re: Diff in Johnson 150 and GT150

Well, i just looked at the title, and its a 90 model not 91...I will check the engine # just to be sure...but Im 99% sure its a true GT model...I am the 3rd owner and the guy I bought it from got it from an older gent who kept it at the lake since day 1...Its going to the shop Monday to get the steering cables changed, i think thats going to run about 350...

I know there is a diff forum on here, but since im typing anyways lol...I have a 22 pitch Raker on it, and want to switch to a 24...called local prop shop and for about 50 can get this one worked up...is having that done going to actually give me a 24 pitch? The prop I have now looks brand new, and dont really want to spend the $ to just buy a new 24....

Re: Diff in Johnson 150 and GT150

No it won't be a true 24 but it'll have more (should have) bite than a 22. Why do you want to increase bite?

Re: Diff in Johnson 150 and GT150

More top end speed. I have only got to put this boat in the lake once..water was rough so I wasnt able to run it flat out...I did have motor trimmed up about 3/4 throttle...no rooster tail like the ol hydro sport had with a raker prop....Hopefull the steering cable will be changed out next week and will be able to take it back to lake next weekend for some running around...Im also looking at an 8" jack plate for it...granyed I wont be running top speed all the time, but when you have "X" amount of time to get back to the weigh in I wanna be able to get there fast

Re: Diff in Johnson 150 and GT150

How do you know you need to repitch the prop if you have not established your top speed rpm?

Re: Diff in Johnson 150 and GT150

My cousin is running a 24 on the exact same boat/motor combo.....I had a 24 on my 150 on the Hydra sports...to me 22 is just a tad small on a GT150

Re: Diff in Johnson 150 and GT150

Quit running them junk (raker) props and try a Merc Tempest or a Yammy prop. I run a Yammy Vmax 15x27 on my Javlin 409DC with a 250 Junkrude and its the BEST prop I have ever run on this boat( tried plenty)

Re: Diff in Johnson 150 and GT150

There are way too many Raker generations to say they'll all "junk" (some are, some aren't). And there are way more efficient props than a Tempest.

Bad - let's look at you set up. When you get it back on the water and get some good numbers, let me know. Sometimes increasing bite can slow you down.

Re: Diff in Johnson 150 and GT150

Thanks Dhadley...boat went to shop today to change steering cables...may have it out by weekend for some testing...I did go by the prop shop...he said is looked as if it had already been worked...but he said it looked like it was worked down, but couldnt be sure til he put it on the bench...The place where I took it said they would even swap me my 22 for a 24 if they had a spare raker...I may go ahead and get the 8" jack plate on while its there, he is gonna call me on price for that...they think they have a used one and will make a deal...Also getting new water pressure gauge and speedo fixed while its there...I will get back with you ASAP after getting it on the lake..

They do have a small lake in back of thier shop, and he said if I wanted a new prop or jack plate, they would test it and get it set up for top speed etc or whatever I wanted for the price they quote, so wont be any guessing on my part if I go that way...they do everything by GPS to get the best set up if I wanted the top end speed...

Thanks for your replys and advice, will let ya know as soonas i get her back

Re: Diff in Johnson 150 and GT150

Well, i finally got to play with the boat this past weekend. New steering feels GREAT!! The owner of the place that worked on boat said my prop had already been worked to a 24...he test drove and rpm was at 5200 WOT..When i got it on the lake, the tach was not working I may have pulled something loose under dash when I installed hummingbird, or when i was pulling TD cable thru side...but anyways...there is a 2 mile bridge over the lake..we were keeping speed with the cars ( est 60+ ) on the hwy, so Im happy about the speed...I know putting an 8" jack plate will help that alot..motor is down on transon so getting it up and back some should get my rpm up more...now I have another querstion lol...when I was trimming motor up at WOT..it would only come up so far? Is there a safety feature or something? if im slow moving, it will trim motor all the way out of the water...but at top speed, i can hold the trim up, and the nmotor will only come so far up...THANKS for all the advice and help...Im going to see if I can get tach to work and somehow verifty the readings..

Re: Diff in Johnson 150 and GT150

When on plane, the trim will only trim out to the length of the two extended trim pegs-no more. If you have the engine trimmed further at idle, then mash the throttle, the engine will slam down onto the two pegs-it is a design feature of the trim system. 5200 rpm is somewhat low-too much pitch. I'd check it again after you finish adjusting the heigh of the engine on the transom. You need to get the engine over 5500, even up to 5700.

Re: Diff in Johnson 150 and GT150

General rule of thumb - if you can use 100% of your trim range and it feels like the boat wants more there are a couple of things to look at. First raise the motor. That will give you some more rpm & speed with the same prop. Then, once you've maxed out the set up for that prop, consider props with more lift.

Re: Diff in Johnson 150 and GT150

Kewl....I def gonna raise motor first....at half 1/2 to 3/4 throttle with trim all the way up...had a nice lil rooster tail, but it went away at WOT..the motor is sitting in the top bottom hole...and I think there are 2 on the mount..so will raise it about 2inches if i remeber the holes right...but I do plan on putting an 8 inch jack plate on it later...Once again, THANKS for ALL the info..Me and kiddo really had a blast this past weekend out on the lake....but the 700Grizzly sitting outside is getting jealous now lol...