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Old 04-22-2015, 01:00 PM   #21
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Yes - belt drive - a pair of them.

Ahh, that's how they do it. With belts you can run the pump at a higher than idle RPM. Then your power limit is just how much power you can siphon off with a belt system. I'll bet your 27hp is right near the limit.

Belt slippage is an interesting theory. The symptoms would all fit I think.
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Old 04-22-2015, 01:22 PM   #22
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Go watch the belts while a helper engages thruster. You should be able to visibly determine if they are slipping. You'll see the pump pulley slow way down.

Guess it was not such a silly question!!
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Old 04-22-2015, 01:42 PM   #23
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I have a dual belt setup on my thruster. I buy matched pairs so they are as close to the same length as possible to minimize slipping.
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Old 04-22-2015, 02:44 PM   #24
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Go watch the belts while a helper engages thruster. You should be able to visibly determine if they are slipping. You'll see the pump pulley slow way down.

Guess it was not such a silly question!!
If the belts slip the pressure will drop. What kind of shape are the belts in and are they matched? Any rust and corrosion evident on the pulleys - an AK vessel damp issue?
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Old 04-22-2015, 03:32 PM   #25
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Hydraulic Filter?
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Old 04-23-2015, 09:56 PM   #26
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Here's what I know after more playing around:

- No belt slipping
- Pressure is lower when this problem occurs (not surprising since pressure controls the power)
- I can only reproduce it right after the main (and hyrdaulic pump) is powered up. It has this problem for a while and then develops full power. After that I can't get the reduced power problem to recur without shutting down and restarting the engine.
- It's a two speed thruster. When it's having this problem it still operates at two speeds - they are just both much lower that when it's working correctly.

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Old 04-23-2015, 10:11 PM   #27
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OK, sounds like whatever controls the system pressure is having difficulties getting started. I think now you need to turn to you system schematics to see how that's controlled. I could offer a number of suggestions, but all of them would be making assumptions about your system that may or may not be correct.
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Old 04-23-2015, 10:19 PM   #28
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Yes - the schematics I have found so far aren't very detailed. I'm going to have to do some more research. It does seem like something is sticking at first - perhaps a pressure regulator. It's guesswork right now though.

I won't get chance to do more research till next week.

Thanks

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Old 04-24-2015, 09:55 AM   #29
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You mentioned a variable displacement pump- If so it is likely a tilting swashplate machine with some sort of hydraulic control that move the swashplate. Since it also runs the stabilizers that use very little flow, and that the pump runs all the time, it probably spends 99% of the time with very little tilt to the plate. Maybe something is a bit worn there and it hangs up transitioning to full flow.

You mentioned that pressure read low when acting up, that observation supports the above.

Belts not slipping, that's off the list.

Something does the "two speed" thing, that would be a suspect, but you noted you still get two speeds but both are weak, that plus seeing lower pressure points to the two speed thing working ok.

Filters not likely as a clog would not resolve itself, usually.

I would be looking at the pump.

Schematics would be REALLY helpful. Could be full of little hyd gadgets that could do the same thing.
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Old 04-24-2015, 10:07 AM   #30
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You mentioned a variable displacement pump- If so it is likely a tilting swashplate machine with some sort of hydraulic control that move the swashplate. Since it also runs the stabilizers that use very little flow, and that the pump runs all the time, it probably spends 99% of the time with very little tilt to the plate. Maybe something is a bit worn there and it hangs up transitioning to full flow.

You mentioned that pressure read low when acting up, that observation supports the above.

Belts not slipping, that's off the list.

Something does the "two speed" thing, that would be a suspect, but you noted you still get two speeds but both are weak, that plus seeing lower pressure points to the two speed thing working ok.

Filters not likely as a clog would not resolve itself, usually.

I would be looking at the pump.

Schematics would be REALLY helpful. Could be full of little hyd gadgets that could do the same thing.
Agree with everything - yes it does run the stabilizers too. I had ruled out the low speed solenoid since I still get two speeds. I will find and copy what schematics I have. As I recall it doesn't show much - a control box, low and high speed solenoids, pump, reservoir, return lines. Not much more as I recall.

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Old 04-24-2015, 10:17 AM   #31
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If there is a filter in the supply line from tank to pump, it could be worth changing that. maybe when pump tries to transition to full flow it gets a pressure drop that slows the swash plate actuator. Turns into a "chicken and egg" sort of thing with regards to what causes the low pressure.

Does problem show up more when fluid temp is low?
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Old 04-24-2015, 11:01 AM   #32
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Of the many possibilities for troubleshooting a hydraulic system, pressure gauges in a few key areas are helpful. One important place would be pressure checks at the thruster inlet, any motor bypass lines and outlet.

A hydraulic shop should be able to supply a guy with the right gauges and know where to install quick connect fittings for the gauges to get plugged in for system checks. This then allows you to isolate problem area which could be the main valve block, check valves, manual valves, thruster motor or hydraulic pump.

Possibly the original install or design is at fault and problems have existed since day one. Wesmar should be able to proved an ideal install schematic to compare to actual.

Yes, everybody claims to love hydraulic thrusters. I am not one on smaller vessels. Electric thrusters are not the menace some say and even Nordhavn equips the vast majority of their sub 60 footers with electric. I debated this issue a few years ago with my vessel and ended up with electric which can run uninterrupted for in excess of one minute, that was the extent of my test. I also went through this with Nordhavn when specing out a new build. If per chance you need some expensive repair parts, it would be nice to have the cost of a 8kw or so electric thruster in your back pocket. The hole is already there.

Last but not least get a really bright flashlight and look at all the system's valve bodies and fittings for hairline cracks and fluid loss.
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Old 04-24-2015, 01:07 PM   #33
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If there is a filter in the supply line from tank to pump, it could be worth changing that. maybe when pump tries to transition to full flow it gets a pressure drop that slows the swash plate actuator. Turns into a "chicken and egg" sort of thing with regards to what causes the low pressure.

Does problem show up more when fluid temp is low?
There is a filter - a huge one. I have a spare too. At that point I should probably flush and service the whole system when I change the filter. Who knows when it was last done.

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Old 04-24-2015, 01:10 PM   #34
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Of the many possibilities for troubleshooting a hydraulic system, pressure gauges in a few key areas are helpful. One important place would be pressure checks at the thruster inlet, any motor bypass lines and outlet.

A hydraulic shop should be able to supply a guy with the right gauges and know where to install quick connect fittings for the gauges to get plugged in for system checks. This then allows you to isolate problem area which could be the main valve block, check valves, manual valves, thruster motor or hydraulic pump.

Possibly the original install or design is at fault and problems have existed since day one. Wesmar should be able to proved an ideal install schematic to compare to actual.

Yes, everybody claims to love hydraulic thrusters. I am not one on smaller vessels. Electric thrusters are not the menace some say and even Nordhavn equips the vast majority of their sub 60 footers with electric. I debated this issue a few years ago with my vessel and ended up with electric which can run uninterrupted for in excess of one minute, that was the extent of my test. I also went through this with Nordhavn when specing out a new build. If per chance you need some expensive repair parts, it would be nice to have the cost of a 8kw or so electric thruster in your back pocket. The hole is already there.

Last but not least get a really bright flashlight and look at all the system's valve bodies and fittings for hairline cracks and fluid loss.
Thanks for the suggestions.

I'm not an evangelist for hydraulic bow thrusters. It just happens to be what's on my boat. Is 8kW enough for an electric replacement? Mine is rated at about 25HP and even then has a hard time if there's much wind. The boat is 80,000lb loaded, full keeled and the bow is about 10' off the waterline. Lots of mass and lots of windage.

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Old 04-24-2015, 01:53 PM   #35
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Thanks for the suggestions.

I'm not an evangelist for hydraulic bow thrusters. It just happens to be what's on my boat. Is 8kW enough for an electric replacement? Mine is rated at about 25HP and even then has a hard time if there's much wind. The boat is 80,000lb loaded, full keeled and the bow is about 10' off the waterline. Lots of mass and lots of windage.

Richard
The standard specs for a N55/60 show a 15 HP Sidepower 24V. Boat weighs around 120K lbs with considerable windage. I've operated them and no doubt it moves the vessel quite handily. Hard to know how many HP your setup is actually putting into the water at "idle".

I'm not saying it is necessarily a good idea, just saying nice to have a price in your back pocket.
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Old 04-24-2015, 03:57 PM   #36
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The standard specs for a N55/60 show a 15 HP Sidepower 24V. Boat weighs around 120K lbs with considerable windage. I've operated them and no doubt it moves the vessel quite handily. Hard to know how many HP your setup is actually putting into the water at "idle".

I'm not saying it is necessarily a good idea, just saying nice to have a price in your back pocket.
Interesting - that's certainly plenty of boat to be swinging around. Yes - I don't really know what the output of mine really is. I don't know how often I have encountered the low power output problem and not noticed. Now I'll be more aware.

I do know that increasing the RPMs makes a marginal difference to the sound (speed) of the thruster. Also, I think the JD 6068T puts out something like 40HP at idle. I have the curves at my boat.

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Old 04-24-2015, 04:20 PM   #37
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Have you tried contacting the manufacturer and running it by them?
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Old 04-24-2015, 04:29 PM   #38
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Have you tried contacting the manufacturer and running it by them?
Not yet - I will do that when I get chance during the day - probably next week. Good suggestion.

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Old 04-24-2015, 04:35 PM   #39
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I have a hydraulic stern thruster, belt driven pump. It has occurred to me hydraulics are really nice. This just an intellectual exercise. The question is this, is it feasible, reasonably workable to have a 12volt powered pump perhaps off the house bank.
Thoughts??
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Old 11-04-2016, 05:19 AM   #40
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Hi there How do i set up my hydraulic thruster to run off generator
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