1999 Catalina 380 - Engine stalling in reverse

[ibossenger]

Engine idle is set @ 1,000RPM, engine (42HP Westerbeke) and transmission (Hurth HBW150 - A2.5, ratio A=2.63, B=1.95) are fine. Equipped with 18RH12 3 blade prop. Engine stalls when engaging into reverse if boat forward speed 3 - 4 knots. (Shifting into neutral, waiting for engine to idle down, then shifting into reverse) Below boat speed of 4 knots we can engage into reverse, increase throttle and all appears normal.
Any suggestions?

[erps]

Shifting into reverse at 4 knots and killing the engine is kind of like popping the clutch on your car in 2nd gear at a stop sign on a hill. I don't think it's a mechanical problem, I think it's just a matter of learning the idiosyncrasies of your boat and then adapting to them.

[Faster]

I'm wondering if your tach is accurate. 1000 rpm is a pretty high idle speed for a diesel, and if your idle is too low then the symptoms you describe make more sense.

We had a 40 hp, same gear, very similar prop and never experienced this behaviour in 12 years of ownership. Idle was set around 600 and we never stalled the engine by shifting to reverse.

btw, IIRC the hurth manual says there's no harm in shifting to reverse at any rpm, so maybe you can get around this by keeping the revs up a bit. Then again, the need to shift to reverse at over 4 knots should be a rare event.

[Valiente]

I agree. I tend to "coast" in neutral as much as possible when docking, and only give a high rev burst of reverse if I'm overshooting before a spring can be put on. My idle is about 700 rpm on a Westerbeke 52, I have the B-W transmission, and a three-blade 18 x 13, so it's not wildly different. I know that when I do reverse out of a slip, I tend to spin the engine up just to avoid prop-walking and to get sufficient way on for steerage. Noisy, but effective.

I can't recall when I've had to hit reverse, actually, if I was going more than four knots (which would put drag on the prop as you shifted to reverse). On the other hand, people who see my boat assume I'm unlikely to stop quickly anyway, and so give us a wide berth.

I anticipate that when I install our new four-bladed, 19 x 15 VariProp this spring, that I will have to learn how to shift all over again, because there is always a definite time lag as the prop blades redeploy. The upside of this is that I expect significantly more low-speed torque with the increased bite of the four-blade, and less drag, of course, under sail when those big blades are feathered.

[Rockter]

That's an unusual one.
Try geting the boat to move the same 3-4 kt speed speed in reverse, then try shifting to forward.
Do you get the same symptom?

[ibossenger]

Thanks - we had a mechanic working on the problem, raized RPM from 850 to 1,000 on his LED digital tachometer to see if we could overcome the stall. This may have made some difference but not much. Had the boat out of the water, cutlas bearing, strut, shaft etc. all seem fine.