Does anyone out there have experience with extendo propellers? My 9.2c has no directional ability backing up, and only goes at 4 knots running the Yanmar 2GM 13 at 2000rpm's. The extendo would enable me to go from a 13" prop to a 14" prop, moving the prop a little further aft. Can the motor/shaft etc handle the change? I really don't know anything about these things. I would love any prop advice - others must have the same issue? And And, while we're at it - am I running my RPM's to low? THe sales man said 2000 rpm's, but the manual says don't run it under 3000. WHat are people running their 2GM's at? Thanks so much, Kim
Extendo Propeller & engine RPM's
- Thread starter Kiminpr
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I can hit 5.5 knots at 2800 RPM with my 2QM15. Regarding directional ability backing up, try applying more throttle backing up. The blades aren't as efficient in reverse and any boat with a rudder will back like crap if there is no water moving over the rudder. Use a short strong burst, then drop it into neutral to see the effect of the burst. When maneuvering in tight locations most of the time I am gliding in neutral, after applying bursts to get her moving.
BobM (again) is right on target. I have a 2GM20F (16hp) and 5.5 knots is right on at about 2750 RPM. We just returned to Jacksonville from Key West and ran the engine most of the way and cruised between 2500-2800 RPM. We have a 3 blade prop and it does make a difference backing down, but you still need to get some speed (flow over the rudder) for it to be effective.
Thanks for the compliment Rok. I try to help others learn from my mistakes ;-)
I learned this one (that you need flow over the rudder to steer) the hard way. I decided it was a beautiful day to show off and sail off the mooring. My Wife, at the helm, followed my directions to a tee. We raised the main, dropped the mooring pendants and we finally picked up enough speed through the water to steer just in time for me to grab the tiller and at least ensure we grounded bow on nearly 180 degrees from the direction we were trying to go in.
My mistake? Thinking that the boat, a relatively weak performer sailing to windward, would pick up enough speed to steer in just a few moments. Instead it only too took a few moments for the wind to push the bow around and my Wife couldn't hold a course due to a complete lack of water flowing over the rudder. The boat was essentially just pivoting on the rudder. It was a (thankfully) low speed disaster...in front of the entire club of course. In hindsight, I am glad I wasn't well known at the time because I'd still be living it down
I should have avoided the whole situation, rookie that I was (and am). I have since successfuly sailed off the mooring a number of times...but the motor is always running in neutral. I also could have just pulled the main upwind by hand (it was a 25 footer) or moved the traveler up to catch more wind before dropping the pendants.
Oh well...
I learned this one (that you need flow over the rudder to steer) the hard way. I decided it was a beautiful day to show off and sail off the mooring. My Wife, at the helm, followed my directions to a tee. We raised the main, dropped the mooring pendants and we finally picked up enough speed through the water to steer just in time for me to grab the tiller and at least ensure we grounded bow on nearly 180 degrees from the direction we were trying to go in.
My mistake? Thinking that the boat, a relatively weak performer sailing to windward, would pick up enough speed to steer in just a few moments. Instead it only too took a few moments for the wind to push the bow around and my Wife couldn't hold a course due to a complete lack of water flowing over the rudder. The boat was essentially just pivoting on the rudder. It was a (thankfully) low speed disaster...in front of the entire club of course. In hindsight, I am glad I wasn't well known at the time because I'd still be living it down
I should have avoided the whole situation, rookie that I was (and am). I have since successfuly sailed off the mooring a number of times...but the motor is always running in neutral. I also could have just pulled the main upwind by hand (it was a 25 footer) or moved the traveler up to catch more wind before dropping the pendants.
Oh well...
Backing & RPM's
Hey BobM Thanks for the advice and your story! - we went out this past weekend and practiced just what you suggested for backing - quick short bursts of speed - it certainly helped - I can't say I've got control back ing yet, but it gave me a starting point. Hauling out Sunday - I've decided to hold off on the prop - take a look at what is down there and do some measurements. I'll use what we've got this year. We also tried running the engine at a higher RPM - it seemed to run the smoothest at 2200 - even more smoothly than 2000. It will be interesting to see how it goes next week with new bottom paint. I'll keep you posted!
Hey BobM Thanks for the advice and your story! - we went out this past weekend and practiced just what you suggested for backing - quick short bursts of speed - it certainly helped - I can't say I've got control back ing yet, but it gave me a starting point. Hauling out Sunday - I've decided to hold off on the prop - take a look at what is down there and do some measurements. I'll use what we've got this year. We also tried running the engine at a higher RPM - it seemed to run the smoothest at 2200 - even more smoothly than 2000. It will be interesting to see how it goes next week with new bottom paint. I'll keep you posted!
No problem...but...
It is actually a negative thing to run a diesel at low RPM. They like to be run at 80% of wide open throttle, otherwise they don't run as efficiently. It is actually recommended that, after motoring into port at low speeds, that you drop it in neutral and throttle up for a minute or two before shutting down.
If your boat won't run comfortably at 2800 rpm (typical for a Yanmar, but consult your manua, mine's a 2QM15) it is an indication that you need to unplug or, better yet, replace your mixing elbow. The mixing elbow is at the aft end of the engine before the exhaust. Seawater is injected into the elbow aft of the engine to cool the exhaust resulting in the water sputtering out the exhaust. A plugged exhaust elbow will result in overheating causing your engine to shut downs. This happened to my friend while he was in rough seas in his Hunter 37 Cutter. He had no fun sailing it into a crowded mooring field last year and admits that it has impacted his confidence a lot. This from a guy who used to sail a Lancer 25 from Boston to Provincetown like it was nothing (he used to own my last boat).
So rev that puppy up!
It is actually a negative thing to run a diesel at low RPM. They like to be run at 80% of wide open throttle, otherwise they don't run as efficiently. It is actually recommended that, after motoring into port at low speeds, that you drop it in neutral and throttle up for a minute or two before shutting down.
If your boat won't run comfortably at 2800 rpm (typical for a Yanmar, but consult your manua, mine's a 2QM15) it is an indication that you need to unplug or, better yet, replace your mixing elbow. The mixing elbow is at the aft end of the engine before the exhaust. Seawater is injected into the elbow aft of the engine to cool the exhaust resulting in the water sputtering out the exhaust. A plugged exhaust elbow will result in overheating causing your engine to shut downs. This happened to my friend while he was in rough seas in his Hunter 37 Cutter. He had no fun sailing it into a crowded mooring field last year and admits that it has impacted his confidence a lot. This from a guy who used to sail a Lancer 25 from Boston to Provincetown like it was nothing (he used to own my last boat).
So rev that puppy up!
By the way, I was nervous last season too, as Triple Play is my first diesel and having a diesel inboard was the biggest learning curve for me. I had zero experience with diesels. The second time we sailed Triple Play we motor sailed the better part of three days and 180 miles from Milford CT to Boston. During the longest leg we motored for 12 straight hours at 2800 RPM. I wouldn't have wanted to try that with an outboard.
I just returned from a two week cruise with a new Campbell Sailor three blade prop. I havea 9.2A with a 2QM15. In calm seas she was making hull speed with rpm a little too low and a bit of light gray exhaust. I plan to have the prop pitch changed from 8 to 7 or 7.5 this coming winter.
I also had some minor engine failures that ended up being microbial blockage of the tank dip tube screen. I learned two lessons: pull that dip tube and clean the pickup screen periodically. The dosing instructions on the antimicrobial containers are just enough to keep a problem from occuring. If you have a problem, give the tank a good shot, maybe four times what the label says. All advice from the Gore Bay Ont mechanic recommended by the Ports Cruising Guide for Lake Huron.
I also had some minor engine failures that ended up being microbial blockage of the tank dip tube screen. I learned two lessons: pull that dip tube and clean the pickup screen periodically. The dosing instructions on the antimicrobial containers are just enough to keep a problem from occuring. If you have a problem, give the tank a good shot, maybe four times what the label says. All advice from the Gore Bay Ont mechanic recommended by the Ports Cruising Guide for Lake Huron.
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