M40d2 timing and carb butterflies not opening

[Skiffboatbilly]

Hello, first post,

I have a 2005 m40d2 that was an old motor that got abused for a few years while I went off to work. I got the time to look at it no and realize someone fooled with everything. I have cleaned all 3 carbs fully and I let still won’t run and I found the timing linkage was swapped with the throttle linkage. I have 2 questions, first, I measured middle of the link to middle of the connectors, and set the linkages to the lengths specified in the “tohatsu 3&4 cylinder manual”. I however do not understand what to reference the degrees from the timing to on my motor. I see the indicator of the degrees but I do not see the crank case reference point. Can someone direct me to where this is? Second question is that my top butterfly does not open perpendicular to the bore when WOT. I have the linkages adjusted to all move at once and together but the top carb is limited by some type of limiting metal stop which stops the top carb butterfly at about 35-45 degrees. Is this normal? There isn’t any way to adjust this so I doubt it was tinkered with but everything I read says they bend that limiting stop to achieve perpendicular in WOT.

 

[Sea Rider]

Welcome to Iboats,

Follow the time avance adjustments to the letter as explained in the 3-4 cylinder manual pages 2-6 / 2/7. The timing vertical marks should be seen stamped side of the set ring and should match the vertical line formed between both crankcase's mating surfaces when the grip rests at idle and wot throttle position.

Don't have much experience with such M40, would you say that all 3 carbs are not opening fully when the throttle stops at the mentioned plate ? if so, the plates limits the carb's openings and the time advance from moving forward and motor running with too much time advance than what the factory calls for.

There's the idiotic belief that by bending the plate the motor will be technically upgraded to a M50 which isn't so. Athough both M40 and 50 shares the same CC powerhead the 50's manifold and carbs are different from those found on the M40 model which limits the HP.

Happy Boating​

 

[Skiffboatbilly]

Sweet, thanks a lot!! Yeah I thought that the crank case boss was referring to the boss fit for the case parts, but some people have a stopper and a separate dial?? I can see that line but the factory linkage setting does not get me that close so I assume I will have to adjust it. Yes, the butterfly rocker for top carb, carb 1, does not allow the carb buttterfly to advance beyond 35-45 degrees or so, however the bottom 2 carbs can open perpendicular to carb bore when the linkage isn’t attached. I don’t think the butterfly on carb 1 could have been fooled with, just weird it’s limited to that degree and that people bend it open, which seems ridiculous because it’s obviously made like that for a reason, but also that it doesn’t open close to 90. If the timing is off, will it try to detonate before the compression cycle is finished and Jack it up?

 

[Sea Rider]

After adjusting everything as the service manuals suggests by the letter, remove the air silencer and check if the 3 carb's butterflies are opening exact same when at full throttle, surely won't find them at 180 deg as will be found in the 50 HP motor which runs with more time advance along carbs opening way more than the 40.

If you want to take out the max HP out of that nice 40, prop it right as loaded generally to a less prop pitch to run towards its max 5800 wot rpm range. Paul probably can answer what you are requesting...

Happy Boating​