Options for a weak Thruster

My windy ole KK Manatee still has its original 5 HP bow thruster. I recently replaced the three blade prop with a six blade, but performance is no better. Has anyone had one of these motors re-wound for more power. How about winding for 24 volt? Any other ideas before I rip it out? Thanks in advance for brilliant feedback & solutions.

Viagra?

Remember I suggested going to an 8hp dual prop thruster when you were replacing the old 5hp thruster? No substitute for horse power. I would go back to the company that told you the dual prop 5hp was adequate for the task and tell them to make it work. Unfortunately you will need to upsize the tunnel and now that will be a major job.

Have a 24-volt bow thruster that spins the boat like a top.

What is the make, model, tunnel size, voltage, and distance from batteries to motor?

Ted

If you are going to spend big bucks , remember the hyd thrusters have no operating time limits.

Age of battery?

Put a voltmeter on motor terminals and read voltage when a helper fires the thruster. See what motor is actually running at.

I have a (I think) 6hp on a single grp 24 batt mounted right at the thruster. I get about 10.3v with motor running. When batt gets old it goes down to like 8-9v and thruster gets real weak. That's my signal to get a new batt.

Do post all the details of your thruster.

Are the cables to the thruster properly sized? Connections solid and not getting hot?
Any forward motion lowers thruster efficiency.

healhustler said:

My windy ole KK Manatee still has its original 5 HP bow thruster. I recently replaced the three blade prop with a six blade, but performance is no better. Has anyone had one of these motors re-wound for more power. How about winding for 24 volt? Any other ideas before I rip it out? Thanks in advance for brilliant feedback & solutions.

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As others have said, look at the system. Give it a good going over. Clean everything, test the battery.



I'd be interested in knowing the specs. The model number or model name would help. Maybe there's a more powerful direct replacement. One can hope.

BruceK said:

Viagra?

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Thank you. I needed a good cackle today.

I've had Ballard Electric rewind thruster and winch motors with limited positive results.

They increase sindings with thinner wire that results in a 10 to 15% increase in power.

The motors run a little warmer after rewind so duty cycle is reduced.

The winch motor had a noticeable increase in retrieval speed, not as much with the thruster.

I don't remember the cost, but I didn't think the results were worth the cost at the time.

The various ways to increase thruster power is thicker battery cables, move battery closer to the battery, install larger motor on existing thruster tube, relocate thruster closer to the bow, install a new, larger diameter, more powerful thruster or install a hydraulic thruster.

Comodave said:

Remember I suggested going to an 8hp dual prop thruster when you were replacing the old 5hp thruster? No substitute for horse power. I would go back to the company that told you the dual prop 5hp was adequate for the task and tell them to make it work. Unfortunately you will need to upsize the tunnel and now that will be a major job.

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Dave: Who are you talking about? I haven’t replaced my thruster. It’s original. Can’t agree more that An 8 HP is the only way to go. Just looking for any options before I rip this 32 year old unit out.

I’ll get the model specs together and post them. Battery power is twin 8D’s, one year old, cable is #2 and the run is 19 ft.

Sorry, I had your post confused with another Manatee owner that had damaged his “weak” thruster and was going to replace it with another 5hp thruster with dual props. I suggested that while he was doing a complete replacement that he should go to a 8hp unit. His insurance was doing the replacement and I thought that it would be worth the money to pay for the upgrade. Apparently his isn’t the only Manatee with an undersized thruster.

healhustler said:

Dave: Who are you talking about? I haven’t replaced my thruster. It’s original. Can’t agree more that An 8 HP is the only way to go. Just looking for any options before I rip this 32 year old unit out.

I’ll get the model specs together and post them. Battery power is twin 8D’s, one year old, cable is #2 and the run is 19 ft.

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I know when I put my stern thruster in I used 0000 gauge cable and my run is about 9’ total round trip. I would look at your cable size, #2 sounds very small for 19’. Is the 19’ round trip or one way?

healhustler said:

Dave: Who are you talking about? I haven’t replaced my thruster. It’s original. Can’t agree more that An 8 HP is the only way to go. Just looking for any options before I rip this 32 year old unit out.

I’ll get the model specs together and post them. Battery power is twin 8D’s, one year old, cable is #2 and the run is 19 ft.

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Before you get to far into it. Take the batteries to the bow thruster and wire them with less than 3' lengths of 00 (double ought). Then try the bow thruster. IMO, length and wire size could very well be your issue.

Ted

I put an 8hp dual prop unit in the stern of my boat. I added a seperate AGM battery very close to it. We were in a marina last year with 30+ MPH wind pinning us to the dock. A fender rolled out from between a piling and the boat. I went out and pushed as hard as I could using my legs with my back to the boat. I couldn’t move the boat even 1/8” off the piling. Then I realized I should try the thruster. My wife activated it and it immediately moved the boat upwind very easily. I was able to reposition the fender. That is the most wind that I have tried the thruster in and was quite happy with the result. My stern has a sundeck with a full enclosure so I probably have as much windage as your Manatee has in the bow. I looked up the recommended thruster on Sidepower’s web site and bought the next size larger. Never hurts to have a bigger thruster.

O C Diver said:

Before you get to far into it. Take the batteries to the bow thruster and wire them with less than 3' lengths of 00 (double ought). Then try the bow thruster. IMO, length and wire size could very well be your issue.

Ted

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Ted,

He has 2 8Ds. I wouldn’t want to be dragging them around, but I agree with the premise.

Comodave said:

Ted,

He has 2 8Ds. I wouldn’t want to be dragging them around, but I agree with the premise.

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Not a problem. I know him well. He'll carry one in each hand.

Ted

Comodave said:

I put an 8hp dual prop unit in the stern of my boat. I added a seperate AGM battery very close to it. We were in a marina last year with 30+ MPH wind pinning us to the dock. A fender rolled out from between a piling and the boat. I went out and pushed as hard as I could using my legs with my back to the boat. I couldn’t move the boat even 1/8” off the piling. Then I realized I should try the thruster. My wife activated it and it immediately moved the boat upwind very easily. I was able to reposition the fender. That is the most wind that I have tried the thruster in and was quite happy with the result. My stern has a sundeck with a full enclosure so I probably have as much windage as your Manatee has in the bow. I looked up the recommended thruster on Sidepower’s web site and bought the next size larger. Never hurts to have a bigger thruster.

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What type/brand of stern thruster did you install - also on my list for a very similar boat. Thanks

Oops - just saw Sidepower - external??

It is a Sidepower SE100/185T. It is a 8hp dual prop unit. Install was simple. It took us 2 days to install it. I used a seperate AGM battery and a 15 amp Pronautic charger dedicated to the thruster battery. I used 0000 battery cable even though the total cable run is about 9’. The hardest part was dealing with the camber of the transom. I cut the large hole and the mounting bolt holes top and bottom. Then I used thickened epoxy to fill between the thruster tunnel and the transom. I used wax paper between the epoxy and the tunnel. The epoxy filled the gap between the tunnel and the hull. I only put in the top and bottom bolts. After the epoxy went off I took the tunnel off and filled the areas by the top and bottom bolts to make it fair. Then 5200 the heck out of the area and bolt the tunnel on. It works really well and comes in handy since my wife handles the bow line and when we dock I have to climb down from the flybridge and by the time I get to the sundeck the stern has usually blown off the dock. I use a wireless remote to thrust the stern back to the dock.

Type is a Vetus TF 12, 3400 RPM, 12V, 3000W, serial 642536/48. I got back to the boat today and immediately pulled the stateroom hatches to check numbers and cable size. As you can see, cables are likely 0 or 00 as opposed to my previous report of smallish #2. Cable run is 19’ one way. I must have replaced the cables along with the windlass cables when in Indiantown several years ago. I’d rather forget my experience in Indiantown, and I guess I did.

A couple of weeks ago I had a Yanmar guy down to survey my engine and told him to replace the dry rotted fuel return lines while he was there. He called me to say that the lines were new. I don’t recall doing that but since I’m the only one doing any maintenance, it must have been me. I’m getting old.

All great points above. After checking the contacts, I’ll probably do the local battery thing to punch up the delivery of juice, but maybe I should have mentioned that it worked reasonably well (not great) in the past. Then came the haul out, bottom job, and then the painter didn’t re-pin the prop, so it spun off on the first use. Then I ordered the replacement 6 blade (vs. original 3 blade) prop. It’s been weaker ever since. I should probably add that the motor doesn’t overheat on long applications. Just out of curiosity, I ran it for a whole minute without throwing the heat breaker.

I believe that my thruster is supposed to be able to run for 3 minutes without overheating. Have you checked the voltage at the thruster when it is running? That is the first thing I would check.

healhustler said:

... the painter didn’t re-pin the prop, so it spun off on the first use. Then I ordered the replacement 6 blade (vs. original 3 blade) prop. It’s been weaker ever since....

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Your power loss troubles follow changing a 3 blade to a 6 blade prop. Or damage from spinning without load after losing the 3 blade one. Could that pinpoint the cause?

I wonder if any local electrical repair shops could advise on a more powerful motor that would directly replace the old one. I believe that moving the battery closer to the thruster would really help. It wouldn't be that difficult if you have a place to relocate the battery near the thruster.

FF's post is bang on the money.
Any new build/major overhaul/rebuild, fit hydraulic, simple effective, less noise and won't cut out.
Its not as complicated as you think and works out far cheaper in the long run.

This is kind of spinning in circles. Sorry for the pun.


Step one is to figure out if your thruster is operating correctly. Do that before entertaining plans to upgrade it in any way.


The fact that all this started coincident with spinning off the 3 blade prop, and replacement with a 6 blade is a vital clue that we didn't have until now. It really shifts all focus to the prop. A thruster prop is no different from a main engine prop. It has diameter, pitch, and some number of blades, all of which combine to produce thrust and load the motor. Just because a prop has 6 blades doesn't mean it will produce more thrust than a 3 blade. A top suspect here is the 6 blade prop, and it should be determined if it's actually correct for the thruster. It would appear that it isn't. Or perhaps it's not installed correctly and is slipping on the shaft?


Once you are back to where you started, THEN evaluate whether you need/want more power, and proceed accordingly.

Sounds to me like the wrong prop. I would consider contacting Vetus to discuss the loss of original power issue. The good news is that clearly the tunnel size is appropriate for your boat. So, if you choose to replace the thruster, replacing the tube (expensive labor part) shouldn't be necessary.

Realistically from a cost standpoint, hydraulic isn't going to be an option as the engine room parts cost will likely double to quadruple the overall project cost.

Ted

Let me know if you want to trash the motor

healhustler said:

Type is a Vetus TF 12, 3400 RPM, 12V, 3000W, serial 642536/48. I got back to the boat today and immediately pulled the stateroom hatches to check numbers and cable size. As you can see, cables are likely 0 or 00 as opposed to my previous report of smallish #2. Cable run is 19’ one way. I must have replaced the cables along with the windlass cables when in Indiantown several years ago. I’d rather forget my experience in Indiantown, and I guess I did.

A couple of weeks ago I had a Yanmar guy down to survey my engine and told him to replace the dry rotted fuel return lines while he was there. He called me to say that the lines were new. I don’t recall doing that but since I’m the only one doing any maintenance, it must have been me. I’m getting old.

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I'm restoring (rehabbing?) Manatee KK36088 that survived a partial submersion in the CA Delta. I have this same thruster, but after much wire changing, solenoid renewal, control switch out, motor rebuild, and general swearing, bleeding, and sweating, I only have the ability to thrust to port. I could work with this, but seems everytime I come to a dock I have to dock to port :/ If you decide to change out the Vetus I would LOVE to have that motor, even 32 years old...Cheers!