How to modify a 200HP Jhonson

[bompapen]

I have a crosflow 200hp Jhonson and want more horses. Anyone know where I can get information for modify this engine without open the block?

 

[Daviet]

Re: How to modify a 200HP Jhonson

Your best bet is to probably buy a bigger engine.

 

[emdsapmgr]

Re: How to modify a 200HP Jhonson

Get a set of early 235 heads from a small bore 78 or 79. 323872/873. You will pickup 10 lbs compression. You should jet up a little if you change to them. You will see a little difference with the new heads. That 200 block should already be machined as a high port block, ported like a 235 but without the bubble back exhaust. Also it has the 235 intake stuffers-stock.

 

[bompapen]

Re: How to modify a 200HP Jhonson

Thats is what I looking for. Thanks for the information. The carbs are the same in both engines?

 

[emdsapmgr]

Re: How to modify a 200HP Jhonson

Typically, the 200 hp has the 1 5/16" carbs, the 235 has the larger 1 3/8" carbs. Your engine will work fine with the 1 5/16". Larger-throated carbs on your engine will negatively affect holeshot and won't make a huge difference on top end. Another restriction you may find on your engine are the power packs. When yours shipped from the factory the installed packs were unlimited rpm packs. Factory porting and carbs on a stock 200 will pull strong to over 6000 rpm. If the packs were ever replaced with new factory packs, the current replacement packs are rev limited to 5800. You can check the part number on the side of the pack with the original factory parts listing. If you are running replacement 5800 packs you'll be losing some hp capability. Check the side of the packs for the number 58.

 

[Faztbullet]

Re: How to modify a 200HP Jhonson

A 10 psi increase in compression will only add about 3-5 hp to engine, doubt you will see much/any mph increase but will be a little more snappy on bottom end.. On a standard pad style hull it takes a average increase of 5 hp to gain 1 mph...