Yanmar won’t hold Rpm until warm

[ScottieD]

My Yanmar will not hold cruising rpm until “warmed up”. Details below.

Engine:
Yanmar 4jh3e (normally aspirated)
1370 hours

Symptoms/description:
Starts fine.

Will reach near full rpm under load (3400). I’m a little over propped.

We typically cruise at 2600 rpm.

On setting out, I run at 1500-2000 rpm for a few minutes until the temperature gauge comes up about half way to cruising temp then set the rpm at 2600

Rpm will slowly (noticeable over 30 seconds or so) decrease. Throttle up gives immediate response and rpm back up to 2600. I will repeat this maybe 2-3 times at which point the engine will hold 2600 rpm apparently indefinitely. Will also go to 3400 rpm at full throttle at this time. All this is under load.

Cruising temperature has not changed.

I have never observed any smoke.

Suggestions on what might be causing the decreasing rpm appreciated.

Thanks,
Scott

[Scubaseas]

Most throttles have a friction adjustment for this issue. Who made your telegraph/shifter/throttle?

[ScottieD]

Originally Posted by Scubaseas

Most throttles have a friction adjustment for this issue. Who made your telegraph/shifter/throttle?

Thanks scubaseas. I’m hoping it is something that simple. The engine was installed by the previous owner, so I don’t know about the installation. Just for completeness, the throttle and shifter are separate.

[Scubaseas]

Look through an Edson catalog or try the S2 owners group. Edson usually has a tension screw on the throttle handle shaft accessed under the compass. I have sailed on a couple of S2s and they had Edson binnacles

[capt jgw]

There's a spring on the governor lever that takes up the slack in the cable when you throttle down. If it wasn't there, the engine wouldn't slow down. That spring is overcoming the friction in the control lever and cable and pulling the governor to a slower speed. As Scubaseas said there's probably a friction adjustment someplace that needs tightening. There's nothing wrong with the engine, this is normal.

[Scubaseas]

Might be this one if memory serves

https://edsonmarine.com/content/EB39...ntrolInstr.pdf

[ScottieD]

Thanks to you both. I will start poking around in the next day or two. And that does look to be the Edson binnacle I have.

[ScottieD]

A quick look at the cable found a potential fudge by the previous owner. Looks like an improvised cable friction device and it did change the throttle arm resistance. There is no friction adjustment at the governor that I could see. Next step to take the compass out. But that will wait until I am near a hardware store of some sort.

[capt jgw]

Tightening that clamp another 1/8 turn will probably fix your problem. It's very common to find a wire rope clamp on a cable to increase friction but that can damage the cable. The pictured clamp looks like it would spread the pressure over a wider area minimizing damage.

[Scubaseas]

There is no friction adjustment at the injection pump. Like capt jgw said adjusting the cable clamp thingy should work OK BUT it tends to make the bowden cable itself wear out faster.

You should be taking your compass off once in w while to grease and check the steering chain, etc. The maintenance is covered in the Edson manual. Pick up some "Super Lube" synthetic grease which works anywhere on the boat.

[ScottieD]

Roger. Thanks for the advice.