Perkins 4108 flywheel

[littledava]

I have a Perkins 4108 with a hurth gearbox in my boat which is a bit of a live aboard / sailing project.
It had long been neglected so I've jumped into it and come across a strange problem, the bell housing assembly is very strange with scope for 2 starter motors so I purchased the type I'm familiar with, the type with 2 bolt holes, big Spring on the front which pull in to engage, it fits in the hole but is not correct spacing to mesh with the ring gear, in fact it is meshed when shouldn't be and would disengage if powered up.
After a complete disassembly nightmare I've discovered that the ring gear is actually on the gearbox side of the flywheel. Has anyone come across this set up? Does anyone have a suggestion where I might get a standard flywheel from or should I be looking at a starter to match existing one?

 

[VicS]

The workshop manual describes two types of starter motor, An Inertia type and a pre-engage type.

Are you trying to fit the wrong type?

 

[littledava]

I am trying to fit the top one, just fitted 2 on a friend's boat, both of them had the ring gear on the engine side of the flywheel opposite to mine

 

[mjcoon]

As Wikipedia says (wikipedia/Bendix_drive) the inertial-throw type is a bit rough and ready and pre-engaged type more complex but kinder to teeth. (Though I thought the throw operated via a helical sleeve as shown in @VicS's supplied diagram, rather than "winding a spring".)

But of course both types of starter have to be mounted at the right distance from the ring gear so the pinion moves into engagement, not out!

 

[VicS]

As Wikipedia says (wikipedia/Bendix_drive) the inertial-throw type is a bit rough and ready and pre-engaged type more complex but kinder to teeth. (Though I thought the throw operated via a helical sleeve as shown in @VicS's supplied diagram, rather than "winding a spring".)

But of course both types of starter have to be mounted at the right distance from the ring gear so the pinion moves into engagement, not out!

That is correct...

The electrical system might give some clue as to which type of starter motor is correct.. The inertia starter will have a separate solenoid but the solenoid for the pre-engage type is mounted on, and is an integral part of, the starter.

I think the pinion moves towards the motor to engage with the ring gear in the case of the inertia starter but is moved away from it in the case of the pre-engage starter. This may explain the difference in position of the ring gear.

 

[scottie]

Not all Perkins were built to same specifications and they were very flexible to the extent that they would build them however you wanted to suit your requirements (I assume if you paid)