Prop shaft anode question

R

reefmagnet

.
May 9, 2011
1,000
Hello all. Well, it's taken time, but I'm finally getting around to the business end of installing the new Betamarine engine into my series 1 Vega. I had to get a custom bearing housing made to replace the standard Vega one which had been removed prior to purchasing the boat. This bearing housing houses a standard 4" long Johnson Cutless bearing. I have assumed until now that I could connect a sacrificial anode to the shaft between the bearing housing and the prop shaft. In doing the preparation to install the drive shaft as the motor is put into place, I've since read that the distance between bearing and propeller should be no more then 150% the prop shaft diameter - which the diameter is 1" in my case - as a rule of thumb. The anodes I planned to use are actually 2 1/2 inches long which would mean that the distance between the rear (front?) of the prop and the bearing housing would need to be around 3" (the cutless bearing will also protrude about 1/4" from the housing to allow easier replacement in the future), or twice the generally accepted limit.

Ok, so the basic question is can I poke the shaft this far out of the housing and not expect problems, or are there better alternatives for mounting anodes?

Cheers - Jeff.
 
P

pjacobs55

.
Oct 30, 2019
1,459
Hi Jeff,
I'm no expert, but Sin Tacha has run this setup since the mid 80's successfully.

I used the same bearing ("BACK") and had to shorten it a bit as the housing is a bit shorter. It still protrudes about 3/8" but is quite rigid, and as it's a metal to metal press fit it becomes "one" with the housing.

Hope this helps.

Peter
www.sintacha.com
 
T

tiempo2010

.
Sep 24, 2008
346
Try and leave a space for water to get into the cutlass - it is water
lubricated. Cut the zinc if you have to.
 
R

reefmagnet

.
May 9, 2011
1,000
Thanks Peter and Brian. I have to confess Peter I saw that picture on your
website, even downloaded it to my technical file (hope I haven't breached
copyright ;) ) and that is basically the same setup with the same anode
that I'd envisaged. Here is a link to the picture of my bearing housing
(before final glassing in) which uses an out of the box "BACK" -


I assume you have no issues with your setup?

Brian, I'm planning to leave a 1/4" gap between the anode or prop to the
end of the bearing. As a related question, I've seen some boats with stern
tube mounted cutless bearings modified with holes forward of the bearing to
allow additional water into the stern tube. I'm using a Volvo BlackJack
seal to help keep the water on the outside so I'm reasonably confident that
this sort of mod isn't really needed??
 
T

tim_klynn

.
Feb 12, 2008
337
When I got my boat, there was about 5" of shaft showing between prop and bearing. The engine only had 80 hours on it, so I don't think it was run much like that. Since then ,I shortened the shaft to about what Peter shows. -tg
________________________________
From: reefmagnet autegraau@...
To: AlbinVega@yahoogroups.com
Sent: Tuesday, May 8, 2012 6:13 AM
Subject: [AlbinVega] Prop shaft anode question



Hello all. Well, it's taken time, but I'm finally getting around to the business end of installing the new Betamarine engine into my series 1 Vega. I had to get a custom bearing housing made to replace the standard Vega one which had been removed prior to purchasing the boat. This bearing housing houses a standard 4" long Johnson Cutless bearing. I have assumed until now that I could connect a sacrificial anode to the shaft between the bearing housing and the prop shaft. In doing the preparation to install the drive shaft as the motor is put into place, I've since read that the distance between bearing and propeller should be no more then 150% the prop shaft diameter - which the diameter is 1" in my case - as a rule of thumb. The anodes I planned to use are actually 2 1/2 inches long which would mean that the distance between the rear (front?) of the prop and the bearing housing would need to be around 3" (the cutless bearing will also protrude about
1/4" from the housing to allow easier replacement in the future), or twice the generally accepted limit.

Ok, so the basic question is can I poke the shaft this far out of the housing and not expect problems, or are there better alternatives for mounting anodes?

Cheers - Jeff.
 
P

pjacobs55

.
Oct 30, 2019
1,459
Hi Jeff, no copyrights on any of my stuff. I've got a lot of "paying forward" to do :)

No problems with my setup, and I motor quite a bit for long distances, especially in the summer. I do have a small water inlet ahead of the bearing ... not sure how effective it is. It's just a hole drilled at an angle through the shaft sleeve ahead of the end of the bearing.


Looking at your pictures, it looks like a solid setup you've built.
Just wondering about the picture of the large PVC pipe beside the fuel tank. What's the story there???

Peter
www.sintacha.com
 
R

reefmagnet

.
May 9, 2011
1,000
Cheers Pete. You give me the confidence to continue with plan A!

re the PVC pipe. This will become a 40 litre tank to replace the old copper
tank. The problems of copper and diesel aside, I decided in the end I
needed a tank that could have a full jerry can of 20 litres thrown in to it
without it having to be nearly empty to do so, which would be the case if
the original tank was retained. it's 240 mm NB storm water pipe. Diameter
wise, it's only slightly bigger then the original tank and will fit in the
original location. The mounts will need a little bit of reshaping and
reinforcement to handle the extra weight. The plan is to make the tank out
of PVC and then finish with a few layers of epoxy or vinylester and
fibreglass. The pen markings are the litres capacity so I could keep
cutting it down when I test fitted to the boat if I had to. Fortunately I
was able to retain the preferred 40 litre capacity.
 
P

pjacobs55

.
Oct 30, 2019
1,459
That's a really inovative solution ... I like it! How about attaching the end caps: are they rubber gasketed or do you use PVC cement, or maybe an epoxy, to glue them on? And the filler neck: can it be epoxyed on? I guess the pipe is thick enough to tap the needed fittings into.

I was concerned what to do if/when my copper tank gave up, but now you've provided a DIY solution.

Thanks Jeff!

Peter
www.sintacha.com
 
G

graceglenda1

.
Aug 16, 2011
35
Just a thought ... would the NFPA or any other agency/surveyor question the material against regs for tankage? It does sound like a great idea tho!!
T
V1690
 
R

reefmagnet

.
May 9, 2011
1,000
Peter, originally I was just going to use it as a mandrel, but then I
figured it would save using a wad of glass and resin and PVC is probably
better to contain diesel then fibreglass anyway. End caps are available.
Bit pricey for what they are but a simple solution though I might just make
the end caps out of fibreglass - haven't 100% decided yet. As a matter of
interest, the glue used for PVC is a solvent glue and actually "welds" the
glued bits together so no problems there. I'm planning on epoxying a brass
plate into the fore end cap and this will be tapped for the return,
breather and sight glass tube style fuel gauge. I'm also going to add two
epoxy / glass baffles as well internally. With the filler neck I'm still
looking at alternatives. At this stage I'm thinking a bit of PVC pipe (with
holes / slots!) passed through from top to bottom so it acts as both a well
for the drain and pickup and the filler neck. This will need to be either
fibreglassed or PVC welded in place - maybe even glued with strips of old
PVC dinghy. Tabbing tape can be glassed around the pipe to strengthen it
and build the diameter for the fill hose. Another option is to glass an off
the shelf filler neck to the tank. The caveat with storm water pipe is that
it is laminated construction and has a core made of PVC foam, so caution is
needed I guess to make sure diesel won't get into the core. I'm not that
concerned because it is easy to seal, but if I was I would use sewer pipe
instead which is solid and much thicker (imho too thick for this purpose).

Thomas, I figured the surveyor will raise an eye brow at a PVC tank.
However there is no issue with PVC and diesel and the only problem is that
PVC can be shattered if hit hard enough. My solution is to enclose the tank
in a few layers of light glass when finished to improve impact strength -
along with some flowcoat to hide the PVC ;)
 
S

SVFlyAway

.
Oct 31, 2019
303
A surveyor may do more than raise an eyebrow in the US since there are a
ton of rules about marine fuel tanks from the USCG, ABYC, and even the EPA.
It could very well affect whether your boat can be insured or not.

A boat in our area was recently blown to bits when an illegal propane
installation was done. The boat was surveyed by one of vessel safety
inspectors and the guy was told that the boat would be a given the safety
sticker, but that he had to fix it before he used the boat. The guy didn't
listen and in a few weeks he was onboard when the two fuel tanks exploded.
He was killed. Granted Diesel isn't all that explosive, but if if leaks it
can make a mess of the boat and the environment and the fines for leaks in
the US could be more than the value of a Vega.

I am upgrading my fuel system and using a blown plastic tank from Moeller.
Not terribly expensive, available in many sizes and some shapes, and all I
have to do is to hook up the hoses. And they are marine certified.
 
R

reefmagnet

.
May 9, 2011
1,000
Point taken Chris. However, I don't think that you can really compare
propane gas installations to diesel fuel tanks - totally different animals.
In fact in my neck of the woods (Australia) diesel fuel is not even
considered to be a flammable material in published hazard ratings (it's
"combustionable" which means it burns, but is hard to ignite)! Technically
my tank will be fibreglass/PVC composite with a stretch of the truth
description as "PVC lined fibreglass" .
I did indeed look at the Moeller range, but nothing "off the shelf" was
suitable and I decided to go the custom route. In my research, all the
boxes are ticked, so providing the construction is of a satisfactory
standard (which it will be - I've had plenty of practice!) there is no
reason to expect any issues. In fact, while doing research I found that PVC
plumbing fittings have been used for many years to make (home made) fuel
tanks for petrol powered bicycles, go karts and the like. My only concern
with a surveyor would be that they may baulk at something that is not a
common form of construction and ASFAIK we don't have any specific
construction requirements for diesel tanks for recreational vessels.
 
P

pjacobs55

.
Oct 30, 2019
1,459
I would seriously question using a non-standard fuel tank installation. You
could wreck the engine with dissolved adhesives, cause an expensive spill,
even void insurance. No place to innovate, my opinion.



Nicholas H. Walsh P.A.

120 Exchange Street

P.O. Box 7206

Portland ME 04112

207/772-2191

Fax 207/774-3940



This email is from a law firm and may contain material that is confidential
or privileged. If you suspect you were not the intended recipient, please
delete the email and give us a call.
 
R

reefmagnet

.
May 9, 2011
1,000
Whoa tough crowd! Now you got me in two minds. Might have to go back to the
mandrel idea. Anyone know if good old fashioned polyester resin and glass
will be up to the job?
 
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