1986 20hp port and polished head

[Dano3578]

Been learning a thing or two about old outboards last couple years. Decided to build a little race engine for a small racing boat. Anyone out there have specs on porting and polishing intake and exhaust ports ? Am I pissing in the wind ?
I already have done a intake manifold and carburetor upgrade to a 35hp

Any other mods that can be done ? I have access to machine shop and pretty well mechanically inclined. Just getting familiar with two strokes.

 

[Sea Rider]

You can also polish the porous piston's heads as well as the cylinder head to a smooth finger condition, that way will collect less carbon building up on them. Some folks shaves slightly at a machine shop the cylinder head to increase compression. Can increase the combo performance propping right the motor to run middle to max of its wot rpm range factory stated as loaded, if lightly much better.....

Happy Boating​

 

[racerone]

File the ports square so they relieve exhaust quicker and get a fresh charge quicker.-----Will give you a 15% boost in power I think.

 

[gm280]

Hit and miss porting and polishing is an iffy game unless you have verified areas to port and polish from other same engines that actually showed real gains. Making things smooth and polished could be for nothing if the gases coming in and leaving are still having to take the same convoluted routes without any change. Oh it looks nice and interesting, but unless you know areas that are hampering the flows of gases from others doing the same type engine and have verifiable gains from them, you may gain nothing for your efforts. Been there and done that with non-marine engines... Also, opening up some things could make your idle a real pain to maintain. JMHO!

 

[Faztbullet]

How big and weight of boat? How many RPM an size prop? Cannot cut the head to add compression as crossflow motor. Strictly for racing or just playing go fast? You do not want to polish anything on intake side

 

[Dano3578]

Thanks for the info guys
As of now I just wanna go fast

Currently on a 1432 johnboat
Eventually wanna build a hydroplane for it