Martec Autostream Feathering Prop

[Ben Frothingham]

Hi All,
Does anyone have experience with the Martec Autostream 3-blade feathering prop? I did some thread searching and some folks talked about shaft modifications when changing props. Any further details would be appreciated. Sure will be happy to get launched this year and get some social distancing out on Buzzards Bay and Nantucket Sound.

[RichCarter]

I have a slipstream. Notes here
http://www.richardcarter.net/repower/Propeller.html

I replaced my shaft at the same time so I had to cut new threads anyway. As I recall, there was an issue with the length of the threads because the hub extends past the end of the shaft. There may have been an issue with the length also to make room for linecutters. You can reach me privately if you want to chat about it. I suggest calling Martec customer service to discuss the threads.

Rich

[Ben Frothingham]

Thanks Rich – we are using the same Yanmar engine but I still have the old RV-20 v-drive. Martec suggests a 20 inch in 3-bladed feathering S-1 version – but all I told them was the engine, V-drive, and boat type – not sure how exhaustive their analysis was. you said you might go a little bigger than the 18.5X12 so maybe 20 is ok. This is a left handed prop, right?

Also, it would require the shaft threads to be modified from the existing 1-1/8″-7 thread to 1″- 8 thread – sounds like a job for a machine shop… Thoughts?

[rdugger]

Ben
I installed an Autostream on Eclipse 11 years ago. I did purchase a SS shaft with the correct thread/taper. Absolutely zero issues. Many sailors in the Chesapeake area seem to use Maxi Props … and it seems they must regularly send them off for a rebuild.
I replaced an 18″ fixed prop with an 18″ Autostream. We have a Westerbeke 63 hp engine. I bought mine from H&H Prop in Salem Mass. They recommended 18×9… I have adjusted the pitch and I’m thinking it’s more like 18×11.
I called Martec today regarding the grease fitting. Gary was very helpful.
Rick

[RichCarter]

Ben
If you read my repower notes, you’ll find that a fast running engine like the Yanmar is not a good fit for the stock transmission/v-drive gear ratio. You could put in a different transmission gear ratio or a different V-drive ratio. Since the RV-20 is at the end of it’s life, I swapped out the V-drive. You should expect your RV-20 to start leaking water into the gearbox soon. That’s the kiss of death for the unit because the case is no longer available.

I would have gone to a bigger prop because I changed the gear ratio and I have a 75hp engine. The more powerful engine can swing a bigger prop.

I know all this is expensive and replacing your V-drive might bust your budget. You can live with it knowing that you don’t have enough bite with the setup you have. Don’t run the engine hard. You can damage the prop by causing it to cavitate.

As I recall, the threads for the new prop were entirely different. I don’t know if you’ll have enough material at the end of the shaft to cut it. Find a local machine shop that specializes in shafts and bring your shaft and prop there. Take pictures and careful measurements. In my case, they put the old shaft on a flat table and rolled it. There was a bend in the shaft, making it useless. I don’t recall what a replacement cost. The whole repower was close to $25K in parts about 10 years ago.

Ben
Call Martek and talk to them about prop size. They will model it for you and tell you what the right size is. Your W63 is a slower turning engine than my Yanmare so I would guess that the OEM prop size should be correct but double-check. My old prop says D20P13L. You’ll want to know the engine rated power at RPM before you call. The P424 displaces about 24000 lbs without beer onboard.

[Ben Frothingham]

Gents, Thanks very much for replies. I spoke with Gary at Martec and he came up with borderline between 19 and 20 inch. We went with 20 inch X 11 and ordered it this week. He was talking about a pitch of 10 inches in reverse. FYI, they no longer make the Autostream S-1 to fit a 1.5 inch shaft – the largest is 1 3/8 inch – reportedly for structural integrity of the prop. I spoke with Scandia Prop in Fairhaven and they saw no problem stepping the shaft down at the end and rethreading it – They ask that I bring them the shaft and both props and they can sleeve the old one to match the new shaft diameter. I think their charges will end up being under $300. I also bought a puller that will fit the approximately 3 inch bolt pattern of the coupling. expensive but the right tool for the job and all of that – I’ll bet Rich made his own… https://skiboatpartsonline.com/Coupling-Puller-Tool?search=puller

Rich, my engine is the same as yours – the Yanmar 4JH3-TE with a 1:1 ratio Borg Warner Velvetdrive and then the ancient RV-20 with the 2.05:1 ratio. The old prop, now to be sleeved and kept for a spare, is a fixed 20X11. It started life as a 20X13 but I assume it was repitched when the PO went to higher revving Yanmar. I think I was getting around 3200 – 3400 rpm out of it at WOT, but didn’t really think to write down the max rpm. She scoots along at well over 7kts under full power, especially nice since our mooring is in Woods Hole.

As for the V=Drive, the water jacket was plugged up when I first bought the boat in NC in 2016. On the trip north she ran hot (because the V-drive cooling was in line with the engine raw water circuit) and a yard in the Solomons cleared it out. After they cleaned it out and restored water flow I immediately started getting milky oil from ingress of water to the V-drive gear box (I suspect they put some holes in the bottom of the water jacket using a screw driver to chip out the crud). So, I did what many others have done and eliminated the water cooling and changed the oil.

The main reason I am changing the prop, besides a little xtra speed under sail, is the damn noise dragging all that running gear around. I’m wondering if the V-drive is noisy from bad bearings or such, or the drive train just makes a racket? Did the RV-26 change that for you?

Thanks everyone for taking time to respond – very helpful.

[RichCarter]

Ben
I’ve had absolutely no issues with my Autostream. When shutting down the engine to switch to sail, I momentarily put the engine in reverse to cause the blades to fold. If they don’t fold, they will freewheel just like a fixed prop. Once folded, there is no need for the shaft break. My only complaint is loss of performance in reverse. Reverse is still there but I must give it a lot of throttle to force the blades to open.

I don’t remember the old RV-20 causing objectional noise when in gear. I had the old W60 engine at the time which was loud all by itself. If you have a lot of noise, you might have a bad bearing. There’s a CV joint inside the V-drive. I’d look there first. I think you can remove the cover there without pulling the V-drive. It’s been many years since I was in there but as I recall, the bearings are generic car bearings.

Does your V-drive run hot when running the engine hard? My RV-26 runs warm even with good cooling flow when running at cruising speed of about 7kts. I assume that the faster an more powerful 75hp engine causes thing to heat up and without cooling water it would run too hot. You might consider using synthetic oil in there, higher heat range.

The RV-26 has an oil pump. If I ran it dry, I could probably put a heat-exchanger in there to cool the oil.

As for a coupling puller, you really don’t need one. You loosen the coupling and pull the shaft back a few inches, slip a socket in there and tighten it back up. This pulls the coupling off. You’ll need longer bolts. You must be careful to tighten the bolts evenly or you’ll warp the coupling or the V-drive flange. The RV-20 bolts are special. Don’t lose them in the bilge. Put a towel under there to catch anything you drop.
Rich

[Ben Frothingham]

Hi Rich

Well, the coupling came off nicely with the tool and happily the shaft slid all the way out with the prop in place and now resides in the back of the car. Do you have any specs on the cutlass bearing. My measurements show 6 inches long and 2 1/16th inch OD. This was measured in place so would love to confirm the size before getting a new one.
this is a good article on replacing the bearing https://marinehowto.com/replacing-a-cutlass-bearing-sleeve-bearing/

I also measured the stern tube once I had the stuffing box assembly out. It doesn’t seem particularly round, at least on the inboard end – approximately 2 1/2 to 2 5/8 inches OD depending on how you measure it. I’m strongly considering the PSS dripless shaft seal and their measurement for stern tube sizes vary by 1/4 inch so I will likely go with the 2 1/2 and hope for a little flexibility.

So the running gear is noisy when freewheeling under sail. With the Velvetdrive there is no way to lock the shaft without some sort of Shaft Lok. Hard to say if it’s particularly noisy when motoring given the noise of the engine. After I disconnected the coupling, I rotated the other shaft back and forth and don’t hear or feel any grinding, clunking or other raspy sounds. So, not sure why it’s noisy when freewheeling. Maybe it’s the transmission – hard to say. I’m resisting the temptation to replace the V-drive right now with the new prop, autopilot, chartplotter, other instruments, etc…sort of maxing out the budget this year.

As for temperature, I haven’t measured the temp of the RV20 when running hard, but while warm to the touch I can lay my hand on it so it isn’t all that hot. Also, I’ve seen posts from other owners that have run this way for years with no obvious issue.

Also, thanks for the tip on getting the prop to feather. Gary at Martec suggested that as well. I have had a max prop on a previous boat and really liked the feathering feature.
Cheers, Ben

[rdugger]

Ben,
I had the PSS shaft seal on our last boat, an ODay 34. We installed a Tides Marine shaft seal on Eclipse several years ago. Very happy with it. I think it is a more robust design.
Rick
Eclipse

[rdugger]

Rich
I’m a little confused. Do you have a Seahawk Autostream FEATHERING propeller or a Seahawk Slipstream FOLDING propeller?
Rick
Eclipse

[RichCarter]

Sorry, I have a Martec Slipstream prop.
Rich

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