Is there more RPM there ?....potentially stupid question....

[ashh]

....but Im not a boat mech so cut me some slack

Doing the routine maintenance and general look over the OB today and found I might be short a few RPM of my max WOT.

I am taking the OB for a service in the next few weeks, but thought I might ask the question here.

The motor is 99 merc 2 stroke.

Picture 1 is with the throttle linkage? at neutral.

Picture 2 is at WOT

Picture 3 shows how much further it can go past WOT with the controls (forward steer) fully forward, about 8 - 10mm.




















IS there a reason for this bit of leeway? like is it maybe adjustment for idle revs?? or do I have a few more RPM waiting to be released?

I hope that made sense......

[trev1]

I doubt it will make any difference (noticably anyway). At WOT, the throttle butterfly should sit nearly horizontal and a few degrees either side of "perfect" WOT throttle position wont alter the flow rate of the carburettor to any great extent.
Also, sometimes the linkages allow the throttle butterfly to go past the full throttle position. I dont know if that applies to your motor but some I've seen will.
If you take off any induction piping, open the choke butterfly and look down the carburettor (engine stopped) you should be able to see if you're getting full stick

[FNQCairns]

Yeah possibly not alot to be noticed right at top end but you may notice a little extra push from cruise or holeshot etc if you floor it.

cheers fnq

[BM]

At idle the throtle arm should be JUST contacting the throttle pickup for the carbs. But refer to your service manual for correct adjustment.

You may even find a setup decal on your airbox.

[ashh]

thanks fellas

[BM]

Just make sure that at idle your carb butterflies are shut and they should pick up almost immediately with throttle movement. Adjust the brass screw (with spring beneath) as seen in the top of pic 1 to achieve this and then check the position of the butterflies at WOT.

A bees dick off horizontal for the butterflies is fine (and a bit more in reality). You dont want the butterfly stop to be the thing that limits your throttle movement as this is what breaks components.

So when at WOT there should be a minute amount of movement of the butterflies (not the 10mm you have, more like 1mm at that point).

Cheers (and yes I'm a marine mechanic)

[gorby]

What revs are you acheiving at WOT and which outboard and boat are you pushing, weight ?? Is your prop correct for it ?