Mariner 3.3 outboard

[dansar]

Hi

My outboard Mariner 3.3 keeps breaking the shearpin. Start outboard and run for 5 minutes and then put into gear. Runs in gear ok until putting back into neutral and then back into gear when it breaks. The hole in which the shearpin fits is a good and doesn't seem to have any wear. So open to any suggestions.............
Am onboard using my trusty dongle but my connection is s l o w so appologies if I do not reply straight away.

thanks

dansar

 

[Talbot]

Assuming you are talking about the 2 stroke

There are two styles of shear pin created for these engines. The original Tohatsu engine used a much weaker one than the mercury/mariner etc replacement. Make sure you have the right one.

 

[Ceejay]

A dodgy batch of shear pins?

 

[Lakesailor]

Non-manufacturer's parts?
I had terrible trouble with a pattern piece fuel connector once.

 

[dansar]

Ok

Interesting replies so far. Any more?

dansar

 

[firstascent2002]

I have always had the same problem and now simply don't use neutral. I start and stop the engine in gear. Has been working a treat for 4 years now.

J

 

[VicS]

Interesting replies so far. Any more?

Engaging gear with the revs too high? / Idle speed too high?

 

[dansar]

Thanks all for your replies. Certainly some food for thought. The engine idle speed I think is about right. There were a few times when by putting the engine into gear it stalled, but by increasing the idle revs by a little did cause the pin to break. So perhaps this could be the problem.

Many thanks all. Again the forum has helped with a problem.

dansar

 

[Rowing Ric]

On the subject of the Mariner 3.3, does anybody know if this was ever sold with just a forward gear, or has it always been forward & neutral? Many thanks.

 

[dingdongs]

if you have anyway of measuring it say with a micrometer you could make yourself one up out of a drill using the end that you would normally put in the drill and not the drill end.these are normally tough and may not shear.you can normally cut through with a junior hacksaw with a new blade in.a dormer drill rather than a chinese one may be better.

 

[NickRobinson]

Shear hell....

My 'new' Suzuki 3.5hp, bought as a back up for Magna, sheared it's pin first time I put it into gear. Revs were low.

I thought about drills too but I thought it may be like putting a nail in a fuse box-

I sourced three 4mm (good fit in this case) mild steel welding rods and now have a life time supply.

I've not used it in anger but have played around in the dock at Hartlepool for an hour, many fwd/ntl cycles, and the pin shows no deformation or wear.

IIRC aren't pins cast iron/steel? IE designed to be brittle?

Nick

 

[dansar]

My 'new' Suzuki 3.5hp, bought as a back up for Magna, sheared it's pin first time I put it into gear. Revs were low.

I thought about drills too but I thought it may be like putting a nail in a fuse box-

I sourced three 4mm (good fit in this case) mild steel welding rods and now have a life time supply.

I've not used it in anger but have played around in the dock at Hartlepool for an hour, many fwd/ntl cycles, and the pin shows no deformation or wear.

IIRC aren't pins cast iron/steel? IE designed to be brittle?

Nick

The spare pins I have onboard are made of brass.

dansar

 

[Lakesailor]

IIRC aren't pins cast iron/steel? IE designed to be brittle?

Nick

The relationship between the tensile and shear moduli is

E = 2*G*(1+v)

E = Elastic modulus
G = Shear modulus
v = Poisson's ratio

so for common steels assuming E = 30,000,000 psi and v = .33 Then G = 11,278,196 psi

You should also use Mohr's Circle.

There are several failure theories that can be used such as the Von Mises and the Maximum Shear theory.

Remember in shear pins the failure (breakage) occurs at the ultimate strength not at the yield strength.
Also the shear pin will be in double shear, therefore the load on the pin is halved.

...............

However; seriously, the usual metals are stainless or brass. If you use a material that is too strong you may damage something inside the drive train or wreck the prop.
Is it the correct prop? If the slots in the prop hub are wider than the pin there will be quite a shearing force when you engage gear as the slogger will allow the drive shaft to turn before the pin engages the prop slots.
Brass is a bit more likely to distort than stainless and possibly absorb the shock.
I took a brass pin out of a motor that had sheared but due to the stretch and rough break was still giving drive.

 

[rosssavage]

Drift alert! I also have a mariner 3.3 - is there anywhere to stow a spare shear pin on / in / around the engine? Most o/b's have a clip to store one, can't find anything on my engine!

 

[RUSSH]

HBM

Drift alert! I also have a mariner 3.3 - is there anywhere to stow a spare shear pin on / in / around the engine? Most o/b's have a clip to store one, can't find anything on my engine!

Bit of Harry Black Maskers and stick it inside the cowling! Never seen a designated storage place on my 3.3. So we might both learn out of this one.

Regards.

 

[daveangie]

Hi all, on Mariner 3.3 i have no emergency stop lanyard, its just a red push to stop button, do i need to replace part with lanyard fitting please ? dave

 

[rob2]

Gleaned from the Tohatsu handbook, shear pins are available in brass or stainless. The brass ones are for use with the plastic propellor and the steel for the aluminium props. I know of people with similar breakage problems, although I haven't had the problem myself. Most chandlers only seem to stock the steel version, which will solve the problem, but tend to chew up the prop hub instead! You may have the tickover a little fast, I've found that the engine won't tickover for a couple of minutes after starting. If you let it warm up it will tickover quite slowly and slip into gear easily, before that it goes in with quite a clunk and the torque loading must be considerable. if there is any wear in the prop hub it will magnify the effect.

Rob.

 

[Rigger Mortice]

When I first had my little Mariner I got through several OEM shear pins (brass). They simply weren't up to the job. I bought a stainless one and, ten years on, I've never had a problem since.

Maybe the brass ones are intended to shear but if the things go just by putting the engine in gear they are more likely to mean you end up in an unecessarily difficult situation for no good reason.

 

[VicS]

Hi all, on Mariner 3.3 i have no emergency stop lanyard, its just a red push to stop button, do i need to replace part with lanyard fitting please ? dave

If you want to use a safety lanyard yes. The button is held out by the clip on the lanyard . When that is pulled off the engine will stop.

Surprised though that you dont have a stop button that takes a lanyard. The parts lists show them for all 3.3 models regardless of age.

Are you sure the clip is not in place with no lanyard or that a previous owner has disabled the emergency operation

 

[Lakesailor]

Hi all, on Mariner 3.3 i have no emergency stop lanyard, its just a red push to stop button, do i need to replace part with lanyard fitting please ? dave

Hi Dave. If you have a question it's better to start a new thread rather than add to an old one. Lots of people will see it's 2 years old and not bother reading.

Others will join in, answering the original question which has probably been resolved a long time ago.

Oh. Yes it would be a good idea to fit a cut-out switch. There have been a few prop accidents reported recently.