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Old 02-06-2018, 22:23   #1
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Seahorse Marine Diesel Duck Vibration - Suggestion needed

I own a 55’ steel Diesel Duck (DD542) trawler yacht, which is a lengthened version of the very successful 48’ Diesel Duck (DD462) built by Seahorse Marine in Zhuhai, China (Zhuhai is few hours from Hong Kong). The boat is now registered in Hong Kong since 2014.

DD542 is beautifully built like its DD462 cousin, except it vibrates. Seahorse knew about the vibration then (unfortunately I did not), but chose to deliver the boat. Seahorse probably felt the problem was simple to fix (relocating the whip bearing), and could be handled without returning to the yard after delivery.

Seahorse has by now tried all simple fixes in sub-contractor yards without success. The boat needs some serious trial and error troubleshooting while sitting in a yard for an extended period. Hong Kong yards are extremely expensive for this potentially very prolonged work, so Seahorse refuses to involve another sub-contractor yard.

The obvious action now is for the boat to go back to Seahorse yard in Zhuhai. But Seahorse will not bring the boat back to its Zhuhai yard, citing an unreasonable China government policy, that the boat must be towed ($$), and they must pay a hefty but refundable bond at 43% boat value ($$$$).

Unreasonable the policy maybe, the policy was known to Seahorse at the time of delivery, and it boggles the mind why Seahorse still chose to deliver a defective boat, and end up hurting everyone including itself.

Anyway I am now stuck with fixing the boat myself, if I do not want to wait for the government policy to change (I have been waiting for three and half years). I have very limited financial means, so I cannot afford any unnecessary trial and error. I hope this post brings me some advices from the community, how to be smart in going about this. Here are some facts, questions, and plans:

1. Vibration increases with load (none in idle) regardless of forward or reverse. Vibration becomes unmistakably noticeable at 1200rpm and increases with rpm. However at about 1900rpm vibration dampens down RELATIVELY; at very high rpm around 2200rpm (engine max out at 2500rpm), vibration not only is pronounced, it goes through cycles of peak and trough every few seconds, as if something is flexing then bouncing back.

2. Compared with the very successful DD462, DD542 has a longer shaft at 4 meters (about 31cm longer than DD462), at the same diameter of 2”. Seahorse (Bill Kimley) is adamant the shaft is not too thin (engine power is 178hp), and this claim seems to agree with calculations by reputable shaft suppliers.

3. However there is a concern where to place the whip bearing for such a long shaft, between the shaft exit Cutlass bearing, and the (forward) thrust bearing. Seahorse experimented with the location and has relocated to the presently just about at the middle of the shaft, about 1.8 meter from either the Cutlass bearing or the (forward) thrust bearing. So the shaft is on one end supported by Thrust Bearing, the other end by the shaft exit Cutlass Bearing, and in the middle by a whip bearing. This should conform the guide line of 40xdiameter (of shaft) which is 2 meters. But there is no improvement on vibration.

4. At this point engine, engine mount, engine alignment, propeller type, propeller size, shaft straightness (checked when pulled out), whip bearing location have all been checked and tried. The latest attempt was to check if the 3 blade Max prop (feathering), new to Seahorse Diesel Ducks, was the cause. A smaller fixed 4 blade prop which generated maximum 50+% power was installed. If there is no vibration the plan was to then go for a 100% sized fixed 4 blade prop. The vibration was less, BUT STILL VERY evident despite the reduced loading. Incidentally Seahorse (Bill’s wife Stella) actually took this as an improvement. It boggles the mind again …

5. I contacted the late George Buehler who is the father of the wonderful Diesel Duck design. George told me about earlier Seahorse Diesel Ducks, and suggested me to buy a new name brand shaft. Based on what he saw with an earlier 55’ Diesel Duck built by Seahorse, the Chinese made shaft “could not hold shape”. The earlier 55’ had such a bad vibration that the coupling came off. The problem was completely fixed by the owner after delivery, by changing out the shaft and re-aligning the drive train.

6. Seahorse (Bill Kimley) is adamant shaft material is not an issue, despite known shaft quality problems with the earlier DD55 (and a couple of DD462s according to George). But I am willing to give it a try. The "cycling of vibration with peak and trough" mentioned in Point 1 suggests the shaft is flexing under load. Such a job in Hong Kong would take a day in a Hong Kong yard, which I can pay IF IT FIXES THE PROBLEM, and demand repayment from Seahorse.

7. I plan to install a proper name brand shaft and re-install the original 100% Max Prop. I ask for advices from the community, if anything else obvious I should account for with my limited financial means.


Thank you all in advance.


The owner of Seahorse Marine Diesel Duck DD542
SeahorseDD54201 is offline   Reply With Quote
Old 31-03-2019, 16:12   #2
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Re: Seahorse Marine Diesel Duck Vibration - Suggestion needed

Hello Dd542 as a transport truck heavy hauler I have experienced this type of vibration disconnect the drive line or leave your vessel in neutral raise rpm slowly if the vibration is present 3 possibilities engine mount not secure or broken front mounted harmonic balancer is not balanced or the engine itself is not centered if these 3 are good check the alignment from your output shaft to driveshaft if this is so far good the hanger bearing should be changed easiest and cheapest to test engine mount secure to hard dock test forward and reverse to see if engine lifts or shifts Fair sea's to you 542
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Old 01-04-2019, 01:21   #3
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Re: Seahorse Marine Diesel Duck Vibration - Suggestion needed

Hey, Dd542-
I just stumbled across this post and realized that it was posted over a year ago. Did you ever find the problem and get it fixed? Was it the prop shaft?

I’m very curious.

Fair winds and calm seas.
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