help modding a 40hp twin yammy

[serious3]

ah (light bulb goes on) mic as in micrometer!!!! i'll pull the carbs during the week and measure the bore size and post up jet sizes etc. while the carbs are off i'll look at the reed stops as well.

[byrdsperformance@tds.net]

It's a good time to install composite reed's .
Steel reed's can break an have resulted in some wiped out engine's.
Composite reed's are some performance gain an safer .if one break's.

[Ballistic]

i dunno about the twin cyl 40hp,but over here they skim .060 off the 50hp 3cyl motors.probably best to stick with 88workcar post ,you can always skim it a bit more.

workcar's point is the way to go.. .060inch? I wouldn't dare to take that much off.

[OUTBOARDER]

Are you allowed to run a low water pick up? go there first and get a clever from Ron Hill.
cyl head is most cost effective first mod, usually, most outboards are made to run third world low octaine gas. remember cylhead geometry, cooling,ign timing and jetting must be all taken into consideration along with a half dozen other things.

What are the rules?

A two cylinder will never make as much power as three cylinders unless you add a expansion chamber and port it until you can here chinese comin out of it!

Once again what are the rules?

[serious3]

with the standard 15p mariner/yammy ali rabbit ear prop i was doing a gps speed of 45.9mph, not bad for a 40hp twin i think! going to borrow a semi cleaver type and see what she does then!

[OUTBOARDER]

with the standard 15p mariner/yammy ali rabbit ear prop i was doing a gps speed of 45.9mph, not bad for a 40hp twin i think! going to borrow a semi cleaver type and see what she does then!

Get a low water pick-up so you can raise the motor, several mph gain..
Do have rules, and picks?

[88workcar]

way back in the day I have shaved .120 and just grinded where it touched on a 3 cyl 40. On my 90 we have cut .250 but that is with a machine shop cutting new squish in it afterwards. What boat is it on put up a picture, that is great speed.

[serious3]

ill be out later and ill get pics then for you, there are no rules as i'm not racing!

[serious3]

one thing i do think i have to change though, i think i have too much positive trim on the motor as flat out she was starting to ventilate, i'm gonna try a 3/8th shim in the motor clamp at the top of the transom, it might loose me a mph or two but will save me over revving. according to the prop calculator over on i**ats i'm pulling 6300rpm with that prop at that speed

[88workcar]

there are no rules as i'm not racing!

This how I like it LOL