Adjusting Lehman 135 Idle?

[GoldenDawn]

My Lehman 135 lowest idle is 750rpm whereas it used to be around 450 rpm. Not sure if recent injector servicing would cause this or if I knocked the throttle cable while recently installing new house batteries. The manual was no help.

Is there a way to adjust the idle speed?

 

[Larry M]

John: Are your readings from the mechanical or a electrical tach? If mechanical, the tach may be off. Have you checked it with a digital tach? If I remember right, our SP135 idled around 650-700.

 

[STB]

Yeah. These are usually 600-700rpm, I think. It is a balqnce between transmission wear while shifting and running smoothly and not stalling upon shift when cold.

450rpm is low enough that I'd be surprised if it was running well at the marina at that rpm, especially in British Columbia much of the year!

As Larry says, a good first step might be a phototach.

Also, what drives your alternators? A pickup? Coming off the alternator wire? Or a mechanical take off? The debugging model varies slightly (but may just be calibration at the gauge).

 

[Cigatoo]

Following…Our single 135 idles around 500. Too low for my liking. Would like to bring it up a little.

 

[STB]

The attached is what I have on the adjustment...

 

[GoldenDawn]

Thanks STB! Just got a note from my mechanic saying the same. I will wait until I have a warm engine and try this.

Not 100% what made it change other than crawling around to install new house batteries - very near the throttle cable . . . .

thanks again.

 

[STB]

Hey GoldenDawn,

Do me a favor and just be sure to check the throttle cable, especially at both ends.

My concern is that the idle could have been set too low for decades, but the throttle cable could have been set with a bit of an advance.

If the throttle cable got bumped out of its clamp, or the clamp got broken, or something got moved, it may now be unreliable. You coukd find yourself trying to slow down pulling into a slip...and that cable is dangling at one end or another, and you are "pushing spaghetti" not your throttle.

I earned the nickname "Capt. Crunch" a while back pulling back into my marina after an otherwise wonderful trip. I'd had a transmission rebuilt and the installer never put the safety wire back.

It was great for a trip or two, but eventually the clamp vibrated open and when I went to shift into reverse I didn't get reverse. I thought the wind was stronger than expected, so gave it significant throttle to seemingly no effect (it was actually a burst forward). Then I put it into neutral, ran down to the lower helm and repeated that exercise.

By the time I focused back on the situation behind the boat, I realized I was going much faster. I was still in forward, not neutral (or reverse).

I couldn't figure which engine it was fast enough because a wind was keeping me straight vs turning, so I shut off both engines. Someone with more experience may have been able to sort it at the upper helm, vs wasting time trying the lower helm, and dock on one engine. I thought I had more time...but I also thought both engines were in neutral.

Regardless, in my case I was out of time and drifted into a friend's boat. Almost got out of it without any damage. Crew was fendering the back as I was pushing the bows apart walking mone past his. My arms proved a few inches to short to fully control it and I bumped part of his bow rail with a metal rub rail protector on my boat. It bent his rail a little and scratched it a little.

I founded a welder and had it fixed for him. But somehow, I am still known as Capt. Crunch!!!!!!!!!

More seriously, it could have been a LOT worse. A diver coukd have gotten run over. The anchor could have come past my dock and hit a person. There are so many really bad ways a lot of control like that coukd have ended.

I ran into the guy who installed the transmission a couple of months later on the dock. I mentioned it to him. He said the safety wire isn't needed most of the time. Sigh.

What to say? I have 4 new things on my pretrip checklist now (2 engine + 2 transmission control cable clamps and safety wire).

This is a really long way of strongly suggesting to check the control system because something change....or, better yet, just because...

As an aside, the same boat I hit almost had a Capt. Crunch moment of its own a few weeks later. It has electronic controls and a battery died. The engine and transmission controls died coming in.

In that case, a passenger thought to try the switch to parallel the batteries and they came back to life just in time to avoid driving over the dock. Different systems. Different failure modes. Different things to check. I guess.

 

[GoldenDawn]

Here's the adjustment - at the end of the throttle cable. Lock nut and adjustment nut. Oops, photo is rotated counterclockwise.

 

[STB]

Here's the adjustment - at the end of the throttle cable. Lock nut and adjustment nut. Oops, photo is rotated counterclockwise.

That looks good, but what I can't see is what is holding the cable sheath in place such that, when the throttle control lever is pushed, the throttle arm gets pushed by the cable vs just the sheath moving.

Do you happen to have a picture of that? Basically how the cable sheath is being held at the location shown in the attached picture (From wholesale marine)

My basic concern is thst something changed, and I doubt it was the calibration screw. I'd feel more confident knowing what it is.

 

[GoldenDawn]

STB
Really good point. I will check the throttle cable at the engine end for repositioning relative to the sheath.

I am single screw, no bow thruster, so sometimes have to come in quite hot and then to reverse to put her on the dock. I would REALLY miss reverse.

Thanks again for helping me think through this.

 

[Pete Meisinger]

450 is too low. Adjust with the cable at one end or the other, don't mess with the injector pump.

pete

 

[av8r]

Using the cable end adjustment to set the idle speed is completely the wrong way to do it. The idle speed should be adjusted with the idle speed adjustment screw on the injector pump, refer to the LH diagram in the first attachment in STB’s post. Best practice is to disconnect the cable and adjust the idle speed, then adjust the cable end so that the idle stop is always contacted before the cable runs out of travel

 

[STB]

Using the cable end adjustment to set the idle speed is completely the wrong way to do it. The idle speed should be adjusted with the idle speed adjustment screw on the injector pump, refer to the LH diagram in the first attachment in STB’s post. Best practice is to disconnect the cable and adjust the idle speed, then adjust the cable end so that the idle stop is always contacted before the cable runs out of travel

Av8r:

I totally agree with you. But, since we know the screw didn't move itself, I think it is important to know what did change to make sure that control cable isn't broken or loose. The potential for a Capt. Crunch event or worse is on my mind.

At this point, it may actually just be the gauge or sensor. I'd really want everything other than that screw positionnverified before touching it. Set it to a bad taxh measurement and good becomes bad.

Once we know there is nothing unsafe in the control configuration, and we have a way to measure rpms well, imcwith you about tuning it, except for, maybe, a hair of preload just to keep it off the stop (just like a setback at the end of the range).

From where I sit, far, far away, I still don't have a good handle on this situation and just want any possible life safety concerns cleared first.

I know someone else suggested adjusting the cables vs the pump. That wouldn't be my move. But, if the cable did move and clamp it back correctly fixes the problem in practice...I also can also understand why some.may feel the inclination to let something that may have worked for years to go back to working for years vs having to re-adjust the pump and then the readjust the cable able to get back to that place.

 

[GoldenDawn]

STB and Others,
I looked for possible issues with the cable sheathing and found something else. The bracket that holds the throttle cable and fuel shut-off solenoid was loose (see photo) - bolts not even finger tight. I tightened these and and now have an idle right around 600 rpm, which I am happy with. So thanks for those that pointed out that the cause of the problem was important - rather than just treating the symptoms.

The engine was rebuilt in 2018 and this bracket would have been removed and reinstalled then. A good reminder to do careful, overall engine checks.

Larry - my RPM comes from a AETNA rpm system with an in-block sensor.

(Photo - the bracket holding the throttle cable has bolts at 8 o'clock and 4 o'clock [partially obscured by white wire] that were both loose despite lock washers.

 

[STB]

Hey GoldenDawn,

Good work. I feel a lot better now!

I have one other idea for you. Do you see where that clamp goes over the top of the control cable? It is prevented from opening back up by a small detent on the clamp. You can see the back of it in the picture.

This is exactly the arrangement that had opened up on me. I don't really know if it was left partially open with the detent not engaged or if the clamp hinge loosened up a hair over the decades and the detent didn't hold it tightly enough against the vibration and pushing and pulling of the cables or if the cable wasn't pushed all the way back in when the transmission work was done.

I do know that it was safety wired before the transmission work and was not afterward.

In any case, I'd like to suggest a little safety wire holding that clamp closed. I am paranoid now, but my controls all now have safety wire and two zip ties each and get inspected before each leg of each trip!

Or, maybe you've opened and closed that clamp during your adventures and it feels nice and tight to you and you are comfortable with it as is. I just figured I'd point out what occured in my case, even though there remains some mystery as to exactly how.

 

[GoldenDawn]

STB
I had to Zoom in to see it but now I do. Looks rusted in place (LOL) but I will add safety wire to prevent opening as per your recommendation. One of the cheaper repairs I can do.

Thanks again for the help with this!