1997 M40C Stalling

[MarvinGabriel]

Nope. I haven’t checked timing. I haven’t had a timing light since cars started timing themselves. Lol

 

[Sea Rider]

Nope. I haven’t checked timing. I haven’t had a timing light since cars started timing themselves. Lol

Don't need a timing light, it's done manually a matter to align the timing plate 25 deg mark to the line formed right at middle of both half mating surfaces when the throttle is set at max grip..

While at idle/neutral, move the gear lever forward and fully throttle to max grip to visually aling, stand right at front ob both matting surfaces and check...Does yours matches same ?



Other part that I would check is the thermo condition, could be that's stuck open and the motor is running too cold ? If found extremely rusted/corroded install a new one along a new thermo gasket.

Happy Boating

 

[MarvinGabriel]

Yep. The timing is good, and the thermostat is good. I replaced the thermostat earlier when I serviced the lower unit. Something that puzzles me is that the timing wheel is advanced, by th throttle, significantly, before the throttle plate starts moving. It seems like it’s supposed to, by design. But that makes no sense to me. It’s kinda like my old 1953 Harley with manual advance...lol

 

[Sea Rider]

The timing plate along the carb should be synched for both to start advancing forward even when the throttle grip is turned, If you hold the timing plate with hand and throttle the grip back and forth lightly, is there any side or up and down play in any of the throttle plastic components, if so, that adds up for some throttle advance delay. This type of obsolete throttle system is not that accurate as the cabled ones, but way faster to synch and repair.

To recap., when at max throttle grip for carb to remain fully open, does the timing plate 25 deg mark stops aligned to the mating surfaces for a spot on carb/timing advance synch ? If not, will need to synch the timing again.

Happy Boating

 

[MarvinGabriel]

At WOT, the timing plate is aligned at 25 degrees. However, before the throttle plate is engaged by that cam plate, the timing is already advanced by about 7 degrees. I have to assume that the throttle linkage plate needs to be adjusted. I’ll see if it can be moved at all.

 

[MarvinGabriel]

Ok, my last post made little sense. I guess I had a senior moment!
1. The timing wheel is correctly situated at WOT and at Idle position.
2. When I twist the throttle mechanism, the linkages begin to move immediately, including the timing plate.
3. The metal cam plate that moves the nylon bushing, to activate the throttle plate does not touch the nylon plate until the timing is advanced to about 6 degrees.
4. It seems possible to move the throttle plate activator to touch the cam plate...but I’m not sure if that’s correct.

unless the engine is advancing the timing 6 degrees, to accommodate the increased demand, this makes no sense at all. I’ve never seen an engine do this, including the old 3 cylinder Kawasaki motorcycle engines (which give me a chill still today!)

is is it as simple as loosening a 10mm nut and adjusting the throttle plate actuator?

 

[Sea Rider]

Being the timing advance and the carb well synched as per your post don't move anything, less the carb nut you plan to readjust. When at idle the carb's throttle cam stays in place, will begin advancing for the carb to open up when the throttle grip is around the middle of the arrow indicator and the dot found at the middle of the speed box. (where you align both for a cold start) Before reaching that zone the carb works witht the air/fuel idle setting and later on with the fixed jets past idle.

When throttle grip is set at min turtle side, how many -less degrees are shown on the timing plate and mating surfaces, would you say 2-3 deg ?

Happy Boating

 

[MarvinGabriel]

Yes...about -2 degrees. So, what you are saying is:

1. The carb does not actually leave idle until the throttle is almost to the cold-start point?
2. The timing still advances well before that point, and should be at about 6 degrees when the throttle begins to advance?

 

[MarvinGabriel]

Like this? In this photo, the throttle is in the idle position.

 

[Sea Rider]

Yes...about -2 degrees. So, what you are saying is:

1. The carb does not actually leave idle until the throttle is almost to the cold-start point?
2. The timing still advances well before that point, and should be at about 6 degrees when the throttle begins to advance?

!-Yes, 2-Yes

If the throttle grip is at 2-3 deg at min and at 25 deg at max grip, both adjustments are correct. Assume that what bothers you is the dead like zone the throttle grip experinces going from -2 deg and the beginning of the cold start point as if doing nothing ? If so..

The Tohatsu 30 having same throttle mechnism, never liked the dead zone found between -2,-3 deg and the beginning of the cold start indicator, so have set the timing advance mark to 0 deg by screwing the B stopper fully in or what needs to be screwed in for the timing plate to stop right at 0 deg. Thie illustration correponds to the 30 HP, assume that's similar to the 40.


Note : will need to reduce the idle rpm carb screw a bit because will increase itself more than a bit when that readjustment is done. The throttle grip respnse will be faster due to having a shorter route than when at -2 deg. If not counting with a tach for the idle rpm reduction, reduce the idle rpm screw to a point that once the boat is floating witht the motor sufficiently warmed up doesn't die when geared forward from neutral/idle grip seting.

Will suggest performing that adjustment after the motor runs top and strong, that's after finding the culprit to your original post...

Happy Boating

 

[MarvinGabriel]

I'm going to put some fresh gas in it, take it to the lake, and test it as it is now. Hopefully, the midrange misfire is gone. If it's not, I'll just put oars on the boat and fish! LOL

 

[MarvinGabriel]

Thanks. My setup is quite different from what you posted in both of your pics. I have only one stopper screw for the timing, to keep it from going beyond 25 degrees. The other one is not drilled through. This may have been done by the setup for the remote, which would explain why this issue started when I converted to a tiller. I did adjust things a bit to get closer to what you are explaining. We’ll see.

If adjusting the timing to 0 deg as explained in previous post that gap between the white roller and the throttle cam shoud decrease a bit,but will never touch at idle. Tohatsu 2 stroke motors with throttle cams. levers will never touch at idle, the pic speaks for itself...



Check the gap between the white roller and the cam, that's at min throttle grip position or idle with readjusted 0 deg timing advance from original -3 deg.

Happy Boating

 

[MarvinGabriel]

Ok, I took it out last night. It’s quite a bit better, but does have a surge at low rpms. It started stalling at idle, when in gear, so I richened up the idle about 1/4 turn and the stalling stopped. No more mid range misfire, but it does have some surging. It runs great at WOT. If I were working on a car engine, I’d be looking for the exhaust restriction or vacuum leak.

 

[Sea Rider]

How many hours would you say the motor has run since day one ? Would suggest doing the following. Remove the air silencer from the carb, drill a 3 mm hole right in middle of the air silencer to match the middle of the carb's throat. Order a can of Engine Tune Up CRC brand, Sit motor on a stand or on the transom at terra firme, start the motor and let it warm up say min 3-4 minutes at idle flushed with ear muffs..

Connect the red cannula to the CRC can, insert it through the tiny hole just drilled and spray several short squirts of product one squirt at a time while the motor runs geared forward at the starting throttle grip position. When spraying motor will tend to miss which is quite normal, let the motor recuperate the idle rpm after each indidual squirt before spraying the second, third and so on. Spray the product liberally all you want, when the motor has had enough, keep pressed the can valve till the motor drops dead. Let is soak for some hours.

Start the motor and run it at idle or geared forward till the heavy fumes dissapears. Put the boat on water and go for a wot spin as if stealing it for say 2-3 minutes to clear the product leftovers inside the combustion chambers. The motor should rev much smoother at any throttle setting and at idle as well and in some cases restore power loss.

Usually install new spark plugs after the smoke has cleared before putting the boat on water. If the motor is healthy will pur as a kitten. If happen to have installed new spark plugs skip it. It's much better to test motors with muffs geared at idle, fast idle or bit higher at load that just at neutral/idle no load. Hope that CRC will do tis homework right and get rid of those smal symptoms. if plan going for CRC decarbon, report your findings..

Happy Boating

 

[MarvinGabriel]

It’s got maybe 200 hours on it. I’ve known the motor since the original owner bought it new, and he literally never used it. It sat in his driveway most of the time. When he used it, he trolled fr walleye mostly, so a lot of idling. I’ve done the ultra strong Seafoam Shock Treatment. I think that essentially what your process is doing, right? At any rate, I’ll give it a try next week, after the tourists go back to the city, and let you know what happens. There are just too many drunks on the lake here, on weekends, and it’s tough to get anything done. Thank you for all your help!

How many hours would you say the motor has run since day one ? Would suggest doing the following. Remove the air silencer from the carb, drill a 3 mm hole right in middle of the air silencer to match the middle of the carb's throat. Order a can of Engine Tune Up CRC brand, Sit motor on a stand or on the transom at terra firme, start the motor and let it warm up say min 3-4 minutes at idle flushed with ear muffs..

Connect the red cannula to the CRC can, insert it through the tiny hole just drilled and spray several short squirts of product one squirt at a time while the motor runs geared forward at the starting throttle grip position. When spraying motor will tend to miss which is quite normal, let the motor recuperate the idle rpm after each indidual squirt before spraying the second, third and so on. Spray the product liberally all you want, when the motor has had enough, keep pressed the can valve till the motor drops dead. Let is soak for some hours.

Start the motor and run it at idle or geared forward till the heavy fumes dissapears. Put the boat on water and go for a wot spin as if stealing it for say 2-3 minutes to clear the product leftovers inside the combustion chambers. The motor should rev much smoother at any throttle setting and at idle as well and in some cases restore power loss.

Usually install new spark plugs after the smoke has cleared before putting the boat on water. If the motor is healthy will pur as a kitten. If happen to have installed new spark plugs skip it. It's much better to test motors with muffs geared at idle, fast idle or bit higher at load that just at neutral/idle no load. Hope that CRC will do tis homework right and get rid of those smal symptoms. if plan going for CRC decarbon, report your findings..

Happy Boating

 

[pvanv]

You do know that seafoam is just mineral spirits, right? Waste of time and money. If looking to decarbon, do as Luis suggested.

 

[MarvinGabriel]

Will do. I suspected as much, due to the smell.

 

[Sea Rider]

Will do. I suspected as much, due to the smell.

Sea Foam is effective if used on constant basis mixed with fuel, if no decarbon product has been used before CRC will take care good care of the M40C. Can spray through the carb's air silencer less product squirts each 50 run hours.

Happy Boating

 

[MarvinGabriel]

Sea Foam is effective if used on constant basis mixed with fuel, if no decarbon product has been used before CRC will take care good care of the M40C. Can spray through the carb's air silencer less product squirts each 50 run hours.

Happy Boating

I'm going to do this as soon as my CRC gets here. I ordered it yesterday. Last night, I went fishing, and the engine ran GREAT. I had to retard the timing one full turn. I noticed while I was messing with it, that if I pulled the timing wheel back, there was enough play in the plastic grommets to pull it back a degree or two. That timing change made all of the difference in the world. So I took the adjusting rod out turned it one turn tighter, and everything got smooth. Still have full power, and it now accelerates like I expect, and it's smooth, finally.

 

[Sea Rider]

If all the plastic throttle system bits have excessive play, change all of them, are darn cheap. Grease them well before installing back on their respective places. Good to read that the motor is revving much better than before...

Happy Boating