i have a gt150 that i bought used and knew it was going to need to be freshened up eventually. I have the 200 intake filler blocks in it, early model 200 heads. well i tore it down for a rebuild and i am looking for someone that knows these things and can do porting for me. Im not looking to go wild just increase some power and some rpms. Any help would be appreciated
Chris Carson in Key Largo FL would be the one to talk to we don't do hop ups here.
http://www.chriscarsonmarine.com
i built a few of those X Flow motors when i got into outboards several years ago due to them being plentiful and cheap. Sounds like you have the parts to build a good one. porting one is a a bit challenging due to the small amount of material that is between the ports already and the rig its going on. the strongest one i built was based on a 87' gt 150 on a 91 skeeter FX175. i had done alot of work stuffing the crankcase and straightening the path of air flow as much as anything, very little porting at all. Set up was the key to making it run, but, after too many runs over 6200 rpm, the stock crank broke in two!i had a ported 235 that pushed the same boat over 80mph but the motor has no bottom end , took forever to get on plane, my GT 150 would eat it alive!Originally Posted by Jbower
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Check your power packs/or pack, you didn't say what year it was. Most where rpm limited to 5800 rpm's or so. Watch the compression as those old crossflows don't like cheap gas and too much timing. Porting is kind of null under that rpm range as well and usually hurts bottom end. Crossflows don't like rpm's above 6000 because they are proned to weird harmonics around 6200-6400 and take a pounding. If you decide to do more than stock rebuild, like said earlier, use someone familiar with em and have lots of $$$$$$ and spare parts. Easiset to just find a 200 block(they have a little more aggressive porting) and use that as a base. also, those old 200's used bathtub heads and actually will hurt flow and lower compression on your motor. GT/XP are great heads. The early 200's made more power via different porting/block/carbs/stuffers(also rated different vs newer crossflows/closer to 180-185)A true XP/GT with all the stock parts makes 162-165 hp anyway,,,
Last edited by omcforever; 12-13-2018 at 07:06 PM.
Age and treachery will always overcome youth and skill !!
Very good info from you guys and I appreciate it. I do have access to a 78 200 block not sure if all of the mounting locations and what not are the same and I know one of the starter mounting tabs are broke but I do have a tig welder. I guess for right now I am going to get ahold of a few guys and see what prices are. I own and operate a marine shop in Indiana obviously I have no problem building this myself and I may just square up the ports and radius corners myself but we will see. Im in the boat and the motor less than 1k and it got me threw the season this year.
Ask the guys on Scream and Fly.
Age and treachery will always overcome youth and skill !!
how much are those heads and intake worth.?
200 crossflow intake and heads nothing special. Bathtub type. Probably $50 or so on EBAY. Filler blocks maybe $50........
Age and treachery will always overcome youth and skill !!
True GT/XP heads that have not been cut/damaged maybe $100-150 set.
Age and treachery will always overcome youth and skill !!
One thing to do is lap in the flywheel with valve grinding compound, it will help on the harmonics.
thanks.i thought I had something.lol
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