59ci mercury tuner

[fs5]

testing the compression has nothing at all to do with how the engines induction system works.
you are only testing the squashed air in the gap between piston and cylinder head in the combustion chamber.

Compression only starts building up once the piston/rings have closed of both the exhaust and the inlet on the way up the stroke.

many builders of engine do a bench test to see about compression when doing mods to cylinder heads.
probably most of the guys on here who the modded stuff do the same with their race engines etc.

its not uncommon to test for compression without inlet manifolds or carbs or exhaust when rebuilding an engine.

The next time you take off your reed housing check it out, and i bet you the compression will be identical to when you put it back on.

obviously you wont believe me, but go check it out or ask the guru's on here.

.

well mate you were right about something,i pulled the reeds on the weekend and did a compression test.it pumped 120psi 2 more then without the reeds fitted.same guage.

[Fast Fred]

four stroke needs to have the throttle wide open or it will come up short on psi. most engine builder cc the head.

[Fastjeff57]

Having the throttle open is also not necessary (contrary to popular belief). Done it both ways and there's no difference.

Jeff

[Fast Fred]

so just so there is no confusion, on two strokes havin the throttle open does not make a big difference when doin a comp test. on four strokes it makes a big difference, it will come up vary short on psi if the throttle is not wide open.

[hightide]

I have a 50 with 60 carbs currently and am wanting to swap to the 60 tuner(part number 8m0045214) and modify it like I've read about here, does anyone have specifications of exactly what they did to theirs? Will there be any fitment issues on my 50?

[MWhite]

Its the same, except at the top where it vents.

[hightide]

So it wouldn't be worth changing? Or are you saying it will fit fine?

[MWhite]

no,,, work on the one u have. the 60 will fit yours fine, but its no different than the one u got now,(sizes wise).

[LittleCharger]

no,,, work on the one u have. the 60 will fit yours fine, but its no different than the one u got now,(sizes wise).

Tried to send you a pm but your box is full.