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Re-jetting modified 200hp merc - help!

J

jeffyham

New member
I am in need of some more performance out of my 1988 200 hp Merc Black Max (carbed) hanging off the back of my 1988 Starflite. I want to install Boyson reeds, velocity stacks, an exhaust housing, and spark plug wires from Bobs Machine Shop. My concern is that I may need to re-jet when done as the air flow in and out of the engine has now changed and I don’t want to fry a cylinder. My local dealer breaks out in a rash when I ask him to do this work as it is hop-up stuff and he has no guidance on how to re-jet.
My question is – has anybody done these, or similar mods and if so, do you have any guidance on proper jetting following these mods? I need all the help I can get.
 
Hey JH, If you do the mods that you are thinking about, you will definitly be rejetting. Do some studying before you start. Depending on what carbs your running, your going to be playing with six jets per carb. Different cylinders may end up requiring different jet sizes. Just removing the airbox usually results in having to bump up one size. Keep in mind that a two cycle engine going lean at 5500 rpm can be damaged in moments. This is one of the reasons your mechanic breaks out in sweats. Also due to the nature of carburators, the motors probably going to run lean in the midrange so you will have to deal with that too. Running more oil in the mix will help in the dailing in stage. I tend to work slowly up to high output. It can take quite sometime to reach peak performance. That being said, these Merc motors respond well to increases in compression, advanced timing, tuning of both the intake and exhaust systems, lightened flywheels and stuff like that. Internally you can get some stronger internal components if your going to really spin her up. Porting can do wonders but requires some advanced skills and lots of experience. I think that if you bump compression, new reeds, tuned intake and exhaust, proper jetting, and revamp the ignition system, that the Merc will sing a tune and make beautiful music.
 
Leave it stock and save your money for a bigger up-grade. Your better off in the long run and will be glad you did it.
 
Big Red said:
Leave it stock and save your money for a bigger up-grade. Your better off in the long run and will be glad you did it.
Click to expand...
What he said, plus it will be easier to sell a stock 200 then a Frankenmotor when its time to upgrade.
 
I have decided to keep this 200 merc stock. I just lost the lower unit as it started going tick tick tick then went south from there. Cost me 2k to replace it. I did, however replace my 5.5 inch jackplate with a 10" from CMC to get the extra setback. THe new hydraulic steering and Big Foot was an upgrade as well.

The boat is doing 66 mph with a full tank and me in the boat with this 1:1.87 gear case and a 25 Trophy + at 5700 rpm. Maybe that nose cone was slowing me down afterall.....

I put more in this boat this summer than it could be sold for....ouch....
 
Hey Jeff, Word is unless your hitting speeds of 80 mph plus a nosecone will slow u down. When u trim the motor up to raise the nose of the boat it drags thru the water deeper than with a stock lower. (Torque master for example.) If u get a chance to try a fury prop give it a go. Works great on my boat. Not a starflite. Run it on a pulsare. Gets on plane great. Huge bow lift. Maybe less stable than the trophy. Seen people pick up 2 to 3 mph with same pitch or one inch less.
 
Thanks. I got the 25 trophy after reading this forum. If I did it again I'd go down to a 24. The 4 bladed prop provides a much less squirrly ride than any of the 3 blades I have run, either thru hub or over. With sn engine of this vintage I am ok with 5600-5800 rpm. The bow lift is good. The boat tracks well, chime walk is less hairy at 60+. it feels like it has more bite than the 3 blades. (duhhh by 25%?) But if I could only get 70 out of this thing...... I just spent 7k in Maint and mods to get from 63 to 66. Not a great ROI unless one is bent on a mission.
 
I really liked the 24P on my Starflite with a 2.4 200. It was good for pulling the kids behind the boat as well as fast runs down the river.
 
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