Got extra RPMs, but no extra power

P

PuffinStuff

Well-known member
Joined
Feb 9, 2014
Messages
76
Fluid Motion Model
C-288 C
Vessel Name
Puffin
Hello Fellow Tugnuts,

Another issue that is confounding us and our near-new 2012 R-29. Just had the new stern thruster put into the boat after the last one flooded with water. There is frequently some water under the stern thruster that I can't track down the source of (on starboard side too, in those small wells), but that is not the topic here.

After the mechanic added the thruster we were so excited to head over to Langley and their tight little marina. The trouble is before we got out of the boat channel (Everett) I realized we had trouble. I brought the revs up beyond "no wake speed", 1500 - 1800 - 2000 - 2400 - 2800 and guess what...no more speed! We maxed out at around 5 knots.

Things to consider: we do have a trolling valve, but have never used it and it is still locked in the "in" position. I checked the transmission fluid and it is present and clear - no evidence of low. It has been suggested that the fuel filter may need changing - and this may be true - but we're getting smooth, solid revs - just no added power to the prop. I did brave the water and actually went in with a mask - nothing was fouling it and I was able to turn it freely.

What could this be? Air filter, clutch...something more sinister?

Any help is much appreciated.

Thanks - Paul
 
Can't help you with the added RPM and no speed issue, but as far as the water goes; this is important. I was recently involved with an R-29 that had a similar issue. Check your bolts holding the exhaust outlet on. These bolts go from the outside through the hull (4 bolts - 1/4-20) and hold the exterior exhaust outlet in place. All 4 bolts on this particular R-29 were snapped. The water was leaking through and his bilge pump was cycling. He was so lucky that the entire assembly did not free up all together since it would have been catastrophic. Don't delay in checking this out. If it is the bolts, you should pull the boat, disassemble the attachment and put everything back in place using life seal or similar product. Let it cure and then you will be good to go.
 
Could your prop key be missing ?
 
Andiamo has a similar if not the same design but we have not experienced anything like you described. I would: check the trolling valve to make certain that is NOT engage. Then, with the tug underway and the RPM's above 2,000 open the engine hood and watch the drive shaft to see if the drive shaft is turning fast. Accelerate the boat further and watch the shaft. If the shaft is turning appropriately fast, the issue is the propeller (providing there are no obstructions or anything that is pulling on the tug). If the prop key is gone (like not installed) the speed of the prop will not match the drive shaft.

Please let everyone know what the cause was on this thread.

About the water in the two wells at the transom. We have this issue from fresh water getting through the cabinet and landing there. Check the weep holes to these areas with a wire and clean out the obstructions and these areas will adequately drain but may not dry completely.
 
Very helpful response!Thanks - you'll have to forgive my ignorance, however, as we're super new to boating. Please describe what the prop key does and how it is located and verified to be in good working order. I'm sure this is a ridiculously silly question, but as we've learned, owning and operating a boat and knowing all the tricks to maintaining and repairing one (even a fairly new one) is another story.
 
There is a slot in the shaft and a slot in the prop. The key fits into that slot and locks the shaft and prop together. The shaft is tapered as is the hole on the prop. This allows for a very tight fit and actually forces the prop on tighter during forward thrust and easier removal when required.
Sorry about my response on your water issue. I misunderstood it. I thought you were getting water infiltrating on the starboard side, but it won't hurt to check those exhaust bolts anyway.
 
I was reading something on these trolling valves and saw the following:

Mechanical Trolling Valve - Notice: Use the trolling valve once daily. The orifice (Figure 6, (4)) can clog when trolling valve is not used for extended periods of time, resulting in unexpected engagement of the valve.

I looked at the cable and level mechanism that connects the simple knob in the cockpit to the transmission, with the engine hatch open. It seemed to activate easily and you could see the level arm move up and down as the trolling valve was engaged and not engaged. I didn't take the boat out as I was solo and in thick fog, but for the record it did not show evidence of being stuck in position.

The info above suggesting it can spontaneously engage without DAILY use caught me off guard.

Regarding the prop key, I'm surprised if it was broken we'd get any thrust as wouldn't the shaft be simply spinning inside the propeller hub? We can do 4- 5 knots, just not anything greater than that.

Is it possible this could be a fuel filter issue? I haven't changed them since getting the boat (at 135 hours new) and we are now at less than 300. The label on the filter on the port side say "replace every 500 hours or at the first indication of power loss."

Any thoughts?
 
PuffinStuff,

I fully agree with what Irish Mist, J&LGray, and Knotflying are suggesting as a likely cause of the problem you describe - that is, a broken or missing prop key. Or, there might be a transmission clutch problem. Or, the trolling valve could be shunting fluid around the clutch. If you follow J&LGray's suggested procedure that should help identify whether it is a prop key or transmission clutch (or trolling valve) problem.

Why do I say that? Well, in your original post, you state, "I brought the revs up beyond "no wake speed", 1500 - 1800 - 2000 - 2400 - 2800 and guess what...no more speed! We maxed out at around 5 knots."

If the engine truly gets to 2800 rpm with a speed of only 5 knots, that seems to discount a fuel filter issue, else you would not get 2800 rpm. Since your R29 is a 2012, I assume it is the Yanmar 6BY2-260 engine. If so, then these are published figures for speed versus rpm:

RPM KNOTS GPH DB-A
675 2.9 0.3 54
1,000 4.3 0.6 64
1,500 6.0 1.3 62
1,800 6.7 1.9 65
2,100 7.9 2.9 70
2,500 9.2 4.4 69
2,800 11.6 5.8 76
3,100 13.9 7.5 74
3,400 16.3 9.4 75
3,600 18.3 10.7 75
4,075 22.3 13.4 77

Source: http://rangertugs.com/RTarticles/Motorb ... Tugs29.pdf

As you can see, at 2,800 rpm the R29 should get about 11.6 knots. This could be a bit less due to weight, waves, wind, and hull smoothness.

You suggested that if the prop key were broken/missing, then the shaft would just spin inside the prop hub without turning the prop. This is not necessarily so, since the prop hub and the end of the shaft are tapered such that forward thrust causes the prop to tighten on the taper, thus giving the prop some frictional attachment to the shaft.

When the transmission is in reverse, do you get normal boat speed? In reverse the thrust would be reversed to cause the prop to try to spin off the shaft.
 
You folks are so GREAT. I truly mean that. I really appreciate you helping us identify the issues we have, like all boaters, from time to time. We bought a Ranger based on this community and the reputation of the company and it has lived up to the hype. We are disappointed we've had more issues than we were first expecting based on the age and hours on the vessel, but they have been fairly minor in the big scheme.

Next question: I'm assuming the boat needs to be pulled in order to inspect this (potential) key issue? Is this the case? I am an experienced diver, so would be willing to get under and investigate if it is something that can be visually confirmed. Perhaps the prop must be actually removed to see what is under the "hub"?

As to reverse, we have very little need to reverse the boat in our slip and always at low rpm/speed, so I can't confirm that, but I did notice a "soft" feeling in the transmission when I initiated backing out of the slip in the marina. Your points are good ones on the revs/versus speed. We do get rpms, so if that doesn't translate to actual speed it makes sense that the fuel filter wouldn't be the issue (still appears to be time to change them out, however, so will proceed with this over this week). Yanmar manual says 250 hours on fuel filters and we're at 288'ish.

Question: if in forward motion is there any potential for the prop to be lost at sea? We left a crab pot out there and I'd like to retrieve tomorrow. If we keep in reverse are we good to go at slow speed or imminent danger to drivetrain?
 
I added the trolling valve on our 2011 R29 and the instructions state that no time should you go over 1000rpm
or you may damage the transmission. While at the dock you could idle in forward and operate the valve.
It should basically hardly turn the shaft as you get to the limit of turning the valve counter clockwise. You should notice
the prop wash is lessened as you operate the valve. Or you could open the hatch and watch the drive shaft as you
operate the valve.
My guess is the prop has a broken key that is inserted in the shaft and the prop, but that at slow speed the prop turns
but at higher rpm the prop is spinning on the shaft.

A prop repair shop can probably give you some expert advice.

Good luck,
Jim
 
If I had to make a bet it is something with the trolling valve or transmission. It would take a lot to shear or lose a shaft spline.
 
A buddy of mine who is a marine tech suggested diving under the boat and (with engine off, of course) wiggling the prop on the shaft and seeing if there is any play in it. Does it move side to side or can it spin on the shaft with the transmission in gear? If so, you know the prop is not locked on the prop shaft. If it is locked, then we have a problem with the transmission.

Might be a good first step.
 
You had said you had the thruster replaced. Ask the person who did the work if they had to remove the prop or mess with anything ? It is just too wierd this happend right after you had work done. Perhaps that may also shed some light.
 
Pay the mechanic at the marina to come down to the boat and look the situation over before you spend money pulling it or anything else.
Sometimes spending money to save money is the answer.
 
Irish Mist's comment is very valid. Many times it is the last thing that you did that causes a new problem.
 
Levitation":214xa1lt said:
Pay the mechanic at the marina to come down to the boat and look the situation over before you spend money pulling it or anything else.
Sometimes spending money to save money is the answer.
Click to expand...

And how nice of Denny to offer to pay for a mechanic! :lol:
 
As it turns out, the mystery is solved. The mechanic that was helping me with the thruster came right down and noticed that he had inadvertently twisted or bent the actuating cable to the trolling valve when working in the crammed quarters. A quick release and reattachment of the cable lowered the lever to the valve about another 3/8", engaging what I assume was the clutch.

A good lesson for me to remember: most often the simplest and most obvious solution is the correct one.

Thanks for all of the advice and quick help. As a side note, the crab pot was empty when we finally got out there!

Paul
 
The check is in the mail
Keep checkin your mail :mrgreen:
 
Now one needs to consider potential transmission damage. Yanmar is careful to warn owners that engine RPM should be no more than 1000 RPM when the trolling valve is in use.
 
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