Prop shaft coupling using a rubber hose and two clamps?

Has anyone ever seen a vessel that uses a short length of rubber hose (like radiator hose) from the transmission shaft to the prop shaft?

This is a big red flag for me which makes me wonder what other corners were cut in the building of this boat...

I know the boat needs cleaning up and basically a refit but not having a reasonable shaft coupling, and the image seems to show the engine is out of alignment with the prop shaft. I suspect that WOT will really heat up the hose due to the pressure and flexing under 200hp output.

Any other opinions?

Thanks!
Stu

Wow...considering the amount of torque delivered to the average prop, I don't think this is good at all.

Almost looks like they couldn't get the shaft out of the Transmission coupler, Cut it and spliced in a shorter shaft. I'd run from this..

hose

What brand of hose is that it would be the kind I need to use on the engine must be really strong

A rubber hose can't survive those torques - That is not a coupling, there is nothing to stop the shaft from falling out of the stuffing box in reverse.

That is likely just a water-slinger, to stop water from the stuffing box from moving up the shaft. Somebody's attempt to deal with leaking stuffing. Should be closer to the stuffing box. Steel hull?

Have another look. Tell us more about the boat? I don't see a problem.

Greetings,
Messrs 99 and Pp. Welcome aboard. "...in the building of this boat..." Is this a NEW build or an "improvement" done by the DPO? (Darn Previous Owner). Depending on what a GOOD survey tells you it may be a worthwhile buy depending, of course, on what you're looking for and what you're willing to invest in upgrades. Pray, tell us more this "customized" vessel...

It is a Roberts 65' vessel with two JD 6068TFM50 engines. It was built in China (unknown yard) and has few hours. The hose is the coupler.

The rudder would prevent the shaft from exiting too far, but would impact steerage.

I think the best thing is to hire a qualified surveyor and haul the boat for a full survey, and expect to put reasonable amount of $ in refit, replacing the couplings and aligning the shafts, and upgrading their exhaust insulation, etc...

if that really is the coupler it wouldn't last more than a few minutes.
I'd say I find it hard to believe but considering what I see on a daily basis (as a surveyor) ..... nah, not too surprised

Greetings,
Mr. 99. IF the vessel in question is the one on YW in Annapolis for $695K, I'd walk away. I think your question of what other corners were cut is quite valid in this case. IF, on the other hand, the same vessel was priced @ $200K, for example, it might be worth investing more $$ in but $695....I don't think so.

Not the coupler. It is for some other function, perhaps to prevent the shaft from falling out when you disconnect the real coupler.

65'? 2" or 3" shaft? Not the coupler.

Xsbank said:

Not the coupler. It is for some other function, perhaps to prevent the shaft from falling out when you disconnect the real coupler.

Click to expand...

Let's hope so!

No way that hose sleeve will carry the torque. It is there for some other reason, and who know what!!! Slide it out of the way and see what is there.

Greetings,
I stand corrected. Get a GOOD survey.

I think this contraption is great idea.I have seen it before.If going astern and your shaft lets go from tranny coupling this will save your prop and rudder.This previous owner was thinking the right things.

I use 2" zincs just forward of my dripless shaft seals to keep shafts from backing out "if." To use a rubber sleeve for similar purpose seems cheap and silly. Yup, wonder what else is questionable.

BTW it looks like steel hull under rubber is already rusting away.

Not trying to start argument but if you have electrolysis aboard a boat (most do ) then the zinc between tranny coupling and stuffing box may not be secure.Still think the rubber hose thing is a great idea.Do not come down too hard on me Sunchaser. LOL

I agree with the comment that the hose cannot take the torque, not even for 1 minute.
Have you verified that there is no shaft beneath? Do both shafts have the same setup?

Iceberg said:

Not trying to start argument but if you have electrolysis aboard a boat (most do ) then the zinc between tranny coupling and stuffing box may not be secure.Still think the rubber hose thing is a great idea.Do not come down too hard on me Sunchaser. LOL

Click to expand...

First of all an anode needs an electrolyte to be active so a "zinc" on the shaft would be completely ineffective. Secondly you can have either stray current corrosion or galvanic corrosion but there is no such thing as "electrolysis" corrosion. No boat has "electrolysis". Electrolysis by definition is a chemical change occurring in an electrolyte due to the passage of electrical current ..... Not too hard on you

Stu-from the picture, that looks to be some short-term solution to a misalignment problem. The fact that there can be very little shaft (on either end) inside the hose and that it only seems to have a single clap on each shaft makes me think this a very short-term. There certainly is not a coupling in the picture. The prop shaft and the transmission appear to be slightly out of alignment. Since this is a twin engine boat, the first thing I would do is check the other engine and examine the shaft/tranny coupling on that one. If it has a standard prop shaft/tranny coupling, then there is definitely a problem. If it has the same setup, I would question why. if there is an alignment problem, there are two solutions: (1) have the alignment corrected and a proper coupling installed, or (2) go to something like an Aqua-Drive system. In either case, the cost of correction can add up quickly and should be a significant part of any negotiations.

In the picture of the first post, to the left of the rubber item at issue is the stuffing box, correct? To the right of the rubber item is a red or rust colored metal collar maybe that's the coupler? Mine is that color.

I recall seeing a mower PTO shaft using what appeared to be hydraulic hose. The mower was a light duty, low cost mower called a Sidewinder SX-70 for urban lawn mowing. It replaced the universal joints with a section of hose. I don't recall the failure rates but know the 540 PTO power was less than 25% of what the JD would output.

I have not seen the vessel first hand but planned to visit soon. The photos were supplied by the broker.

I would replace the stuffing boxes with dripless boxes and add new shaft couplers, and then align the engines to within 10,000ths of true. or bail on the whole project...

I have not decided which route I'll take yet.

Thanks!

Greetings,
Mr. bp. "...This electrochemical corrosion is also known as electrolysis..." from this article: electrolysis in yachts
Time to update your Chem 101.

I agree with MYT, that must be a solid shaft and the hose is there for some other, odd, reason. Have you loosened the hose and looked under it?

Iceberg said:

Not trying to start argument but if you have electrolysis aboard a boat (most do ) then the zinc between tranny coupling and stuffing box may not be secure.Still think the rubber hose thing is a great idea.Do not come down too hard on me Sunchaser. LOL

Click to expand...

I'll LOL too, dry air corrosion is pretty slow. And the retaining pins are not zinc which is why they hang on the under water shafts for so long even though they are half or more gone.

If not a shaft zinc, then one can use other 2" metal clamping devices if they so choose. Hard to beat the zincs though with them already having a pretty good 2" shaft connection design.

RT Firefly said:

Greetings,
Mr. bp. "...This electrochemical corrosion is also known as electrolysis..." from this article: electrolysis in yachts
Time to update your Chem 101.

Click to expand...

Just because some boaters website calls it "electrolysis" does not make it so.
There is a scientific definition of the word and it is as stated " a chemical change in an electrolyte caused by the passage of electrical current '.

people who use the term "electrolysis" (Check SAE, US MIl Spec definitions or the International Society of Electrochemistry or the Journal of the American Chemical Society or a host of other reputable organizations ... anything but some boat website.

oh by the way .... NACE (National Association of Corrosion Engineers) does not agree with you (or the boat website)either.

Most people who use this term lack an understanding of electrolytic corrosion, galvanic corrosion and/or stray current corrosion and often confuse them when each has a very specific meaning.

I am hosting the ABYC Marine Corrosion Analysis course at Port Credit Yacht Club in March. this four day course is a bargain at $875us. Send me a pm if you'd like to sign up.

Oh for crying out load, it's obviously not a coupler. Nor is it designed to stop the shaft from sliding out IMO. Based on the white patch I see in the photo I'd say it was installed to be used with a photo tach to measure shaft RPM.

Did April 1 come early this year?

Capt.Bill11 said:

Oh for crying out load, it's obviously not a coupler. Nor is it designed to stop the shaft from sliding out IMO. Based on the white patch I see in the photo I'd say it was installed to be used with a photo tach to measure shaft RPM.

Click to expand...

Nice catch.

I go with Capt Bill. White spot for a tach. I think it is a rusty coupler on right. Lots of rust makes me like the buy it for 200k vs 695k plan. There is solid shaft alloy under the hose. Detail oriented vessel and engine surveyors are a wonderful thing.

Greetings,
"Nice catch." Possibly but not necessarily. Could be part of the hose...

If for rotational measurement why not a piece of tape with a mark? Anybody ever seen a piece of hose used with a strobe light?

I suspect a packing gland drip stop which would account for the developing hull rust under it. But why not ask owner?