Proper gear shifting on Yanmar diesel

[takeajourny]

So should be a very simple question but important for me in terms of boat operation. Recently purchased a Hunter boat with Yanmar 16hp diesel inboard. Never had a boat with an engine of this kind. It has two levers, one for shifting gears (Forward - Neutral - Reverse) and one for throttle. My questions is: do I have to throttle all the way day before switching gears from Forward to Reverse? Or can I just leave the throttle say on 1500 RPM and shift to neutral and then in reverse?

[chris95040]

Originally Posted by takeajourny

So should be a very simple question but important for me in terms of boat operation. Recently purchased a Hunter boat with Yanmar 16hp diesel inboard. Never had a boat with an engine of this kind. It has two levers, one for shifting gears (Forward - Neutral - Reverse) and one for throttle. My questions is: do I have to throttle all the way day before switching gears from Forward to Reverse? Or can I just leave the throttle say on 1500 RPM and shift to neutral and then in reverse?

Try it!

J/k - yeah, you usually don't want to shift unless you are below 1000 RPM.

[Cheechako]

Throttle back.

[Calif.Ted]

And I like to give the propshaft a moment in neutral to slow or stop before shifting into the other direction.

[takeajourny]

Ok so from what you guys are saying definitely throttle back but under 1000 rpm / slow idle speed still ok to shift? Btw thanks for the quick replies, taking the boat out tomorrow morning so it's nice to get a few things resolved before then.

[a64pilot]

Bring her all the way back to idle and shift to neutral, pause a couple of seconds before going into the other gear, do not shift at 1500 RPM. Sometimes you shorten that pause when you have to, but always shift in idle.

[Sailmonkey]

Most gear manuals say it's only permissible to shift above idle in case of an emergency stop or similar......shifting at speed will (when, not if) tear up components.

[takeajourny]

Got it!

[uncle stinkybob]

My Yanmar 2QM15 manual say that the trans is designed to shift from forward to reverse at full throttle in an emergency. Not something I'm going to try unless it's an oh s%&t moment. I back it down to 1000 - 1200 then shift and it's always been a smooth.

[Xthewater]

If you don't shift to neutral at low rpm, pause, then shift in to gear. The damper plate between Trans & Engine will get quickly destroyed.

[TrentePieds]

Quote: "My questions is: do I have to throttle all the way day before switching gears from Forward to Reverse?"

Quote: "... is designed to shift from forward to reverse at full throttle in an emergency."


The fact that it CAN be done doesn't mean that it SHOULD be done. i find it very difficult to conceive of any circumstances arising in a boat that moves at five or six knots that would require a "crash stop" involving a shift at 1,500 RPM.

At 6 knots you move 10 Ft/sec. For TrentePieds to move her own length when she's going fast enuff to climb her own bow-wave takes over 3 seconds. To move half a cable takes half a minute. So how could you EVER be "taken by surprise" to such an extent that a panic stop would be required?

When you maneuver, do it with sufficient "situational awareness", and with enuff foresight, that you leave yourself sufficient time to come back from "full ahead" to "dead slow" ("idle to us yotties) over a period of 5 seconds or so. Then count to three. Then shift from "ahead" on the tranny to "neutral", count to three, and shift to "reverse" and count to three. Then, but not before, bring the RPM to what the situation calls for.

Following this MO is a fundamental aspect of ship handling.

You can buy "single lever controls" that have but one lever instead of two at (each) steering station. The mechanical linkage of these SLCs is designed to automatically take care of the procedure I outlined above. The shift-lever ON THE TRANNY cannot operate if the control lever ON THE ENGINE is not in the "idle" position.

That is obviously a boon for such as fail to learn to do the procedure correctly on a system using two levers.

TrentePieds

[fryewe]

Originally Posted by uncle stinkybob

My Yanmar 2QM15 manual say that the trans is designed to shift from forward to reverse at full throttle in an emergency. Not something I'm going to try unless it's an oh s%&t moment. I back it down to 1000 - 1200 then shift and it's always been a smooth.

If your 2QM15 is mated to a Kanzaki KBW-10 transmission, you can shift at full throttle if you wish. The transmission output shaft is always engaged, and has two clutches, and the shifter only selects which clutch is engaged. Selecting the alternate clutch at high engine speed will wear the sintered copper clutch plates more quickly, and reduce their useful life. I wouldn't do it as a normal practice, especially on an older engine such as the 2QM15 whose parts are both harder to find and expensive...those clutch plates are $50 each, and your transmission has 8 of them, and the 7 steel plates between them are about $20 each.

The torque on the engine and the damper plate is always in the same direction, and if you shift smoothly from forward to reverse, there should be no significant spike in torque that would compromise the plate or its springs.

[hamburking]

Agreed, low revs for shifting.

Also, don't try to ease it into gear, give it a good solid shift (to or from neutral) and be rewarded with a THUNK from the trans...this is good...means the clutches are in good shape. If you ease it in gently, you allow the clutches to slip, inducing excess wear. The PO of one of my boats, equiped with a yanmar 2GM, always eased it into gear, and I was left with the massive bill to resurface the transmission clutch plates.

To check your trans clutches, watch the prop shaft and shift into forward. There should be a nice solid THUNK, and the shaft spins. If the shaft slowly accelerates, you've got slippage. Once you have slippage it gets worse really fast.

[Sailmonkey]

Originally Posted by fryewe

The torque on the engine and the damper plate is always in the same direction, and if you shift smoothly from forward to reverse, there should be no significant spike in torque that would compromise the plate or its springs.

except for all that rotating mass behind the gear changing direction......maybe that could cause a significant spike in torque.

[ur2slo]

Put it in second and pop the clutch at about.........oh, wait different, sorry.

har har

I have a Yanmar, clunks, are good!