Throttle adjustment question

[Mn carguy]

I took the whaler out for it's maiden voyage. The motor ran great but I had to move my 100 lb wife to the bow to get it to plane. The tach is inop but it didn't sound like it was hitting full rpm. Back at the garage, I put the throttle in the full open position but it looks like the cable wont allow full operation. I've looked for throttle linkage instructions but can't seem to find any. If the cable is stretched, do you adjust it at the carb end or the throttle end?

[99yam40]

I do not think they stretch, but there is a threaded connection on the motor linkage where the cable attaches.

more than likely there are more problems than cable stretching

[Mn carguy]

more than likely there are more problems than cable stretching

That's a little vague. Such as?

[99yam40]

timing not advancing as it should,
fuel pump leaking causing # 3 cylinder to get too rich,
bad plug or wire,
main jet plugging,
there can be many things that could cause motor to not run properly.

being the maiden voyage, do you know if this rig was set up properly and has it run up to 5500 before?

[Jason2tpa]

99yam, you missed it so allow me.

It's helpful to those that can help you if you reply back with your engine year/model.

Unlikely the cable has stretched, more likely the cam roller is not positioned correctly. Take a look to confirm the notch on the roller is lined up with the notch on the throttle arm when the throttle control is neutral.

[boscoe99]

C40TLRA I would guess.

[Mn carguy]

timing not advancing as it should,
fuel pump leaking causing # 3 cylinder to get too rich,
bad plug or wire,
main jet plugging,
there can be many things that could cause motor to not run properly.

being the maiden voyage, do you know if this rig was set up properly and has it run up to 5500 before?

I'd thought of some of this. Last week, I did some basic stuff (changed plugs, gear oil, etc) and I pulled the plugs after the run yesterday and they looked good. I don't know if it was ever set up properly and I'll have to get a tach on it to see what rpm it's running at. The motor runs really smoothly so I don't think it's really running improperly other than not able to make full rpms.

I know that this can be a sign of over-prop but in reading the whaler forum, the 13" that's on there should be correct. I'm back to the throttle adjustment as when it's wide open, the black plastic cam that opens the carb slides isn't against it's stop and I can move the slide rod that connects the three carbs about 3/8s of an inch by hand.

[Mn carguy]

99yam, you missed it so allow me.

It's helpful to those that can help you if you reply back with your engine year/model.

Unlikely the cable has stretched, more likely the cam roller is not positioned correctly. Take a look to confirm the notch on the roller is lined up with the notch on the throttle arm when the throttle control is neutral.

I'll take a look today. Thanks.

[99yam40]

part of the link and sync is verifying the idle and WOT timing.
check what is easy to verify first.
and then go after the harder stuff.

with all of this said, I have seen cables with slack in the movement before.
make sure the cables are good along with all connections.

Get someone to help and while running the boat WOT see if pushing the throttle linkage farther does any good before chasing it very long.
also use a timing light ,verify the correct timing.

A previous owner of my C40 drilled out the main jets, it took me a very long time figuring out why I had a WOT miss.
but it runs well now that I replaced all 3 mains

[Mn carguy]

Get someone to help and while running the boat WOT see if pushing the throttle linkage farther does any good before chasing it very long.
also use a timing light ,verify the correct timing.

That's a great idea, thanks. One of the things I have to do is raise up the motor a couple holes. On the test run the AV plate was buried. I'll get it up to it's correct position, take it for another run and check WOT by hand. I have a timing light buried somewhere in the garage but I haven't used it since I sold my 68 Deville convert about 10 years ago. Thanks again.

[Mn carguy]

Well, I'm getting closer. Thanks to all the suggestions. After messing around with the throttle cable, I realized that it's unlikely to have stretched as it pushes the throttle rather than pulling it. I noticed that the roller on the throttle shaft wasn't contacting the throttle cam. I tried to loosen the screw that would allow me to rotate the cam. Wondering why it wouldn't come loose and thinking 'there's no way you should need an impact on a carb screw" I had a brain flash.

The screws are LEFT HAND THREADS. Yikes. I got it adjusted though now I've got a slight hi rpm idle issue. I brought the engine up one hole. Both of these made a huge difference. I bought an inductive tach which was a complete waste of 30 bucks. Idle speed seems right but wot reads 3800 rpm. The A/V plate is still a little low but I hit 36 mph on the GPS and time to plane was about 5 seconds. I'll have to bite the bullet and get a real tach but it sounds like I'm pretty close to spec. Up one more hole and sort out the idle and I think I'm good.

Thanks everyone and if you want a peek, take a look here: https://www.youtube.com/watch?v=SeAg_ePM1vo

[pstephens46]

2 stroke people weigh in. Would anybody say that motor sounds like it is running above 3800rpm? Did you have it trimmed up at all? Porpoising a bit too, first half before the wake...

[99yam40]

I would not think a 40 would push a rig 36MPH running at 3800 RPM

get a service manual for that motor and follow the link and sync procedure. needs to be done each time you put the carbs back on to get them all opening and closing the exact same. Plus make sure timing is in spec at idle and WOT

[Jason2tpa]

Enjoyed the video. Son of a gun was gettin' squirrelly at the end

Well, as a former owner of 2 yam small block 2 strokes it does sound like you're winded out to WOT. I hear this around the 25sec and 1min marks of the video. I do find it highly unlikely the rpms are only 3800, strictly because the engine pitch would be lower.

I also find it very unlikely the boat topped 36mph, even if I hadn't watched the video. I can't tell if your dauntless whaler is the 15' or 18' model. The 15' model dry weight is just under a 1000lb, your engine just under 200lbs. Add your weight plus fuel weight and your total weight is around 1350lbs. I just seriously doubt a 40hp engine is going to push 1350lbs 36mph. If your whaler is the 18' model, I'm positive the 40hp will not push a 1 ton boat over 30mph.

While the boat was experiencing instability (porpoising) were you trimmed down? I didn't see you make a trim down adjustment during this time to counter the porpoise effect. I ask because if you move the engine up one more notch this will only add to the instability. Assuming your boat is the 15' model, small boats like this are tremendously affected by the weight in the boat and where the weight is located. Luckily you have PT/T to help with this.

When I had a 15' fiber hull like yours with a 25hp 2s, I'd keep a cinder block in the boat that I broke in half. If I needed some weight up front, up would go the 1/2 or full block inside the compartment. Need weight in the rear, port, starboard, etc. Just move the blocks around. Thank goodness I no longer have to do that anymore. Though I did become an expert with small boat weight distribution, so theres something.

[Jason2tpa]

I'm back to the throttle adjustment as when it's wide open, the black plastic cam that opens the carb slides isn't against it's stop and I can move the slide rod that connects the three carbs about 3/8s of an inch by hand.

The rod you speak of that connects the three carbs....when the throttle is positioned wide open, the 3 carb valves (some call butterflies) should be completely open. If your able to open valves further by hand using rod with throttle positioned wide open then carbs are out of sync. Im not 100%, but I believe the carb valves open completely at or around 3/4 throttle.