starter motor swap

[Pierre_Smits]

Hi, last weekend I swapped engines (&gearbox) since my piston rod broke and destroyed the cylinder block ... :-( My 'new' 1800 marina engine from 1977 has a pre-engaged starter motor but my previous 1800 marina engine had an inertia. I am a bit lazy and do not want to change electra when not necessary needed.
If possible I'd like to install the inertia and use cables as they are set now.
On the forum I read that some people did a straight swap others claimed that some ring (forgot the name, the one with the many teeth) had to be changed, swapped 180degrees. What is true?
Attached the destroyed engine (see hole near oil filter) and 2pics of the swap
thanks, Pierre

[donsayers]

Re: starter motor swap

The two types of starter engage the pinion into the flywheel teeth in different directions. So ideally the flywheels need to be swapped as well, so that the little bevels on the teeth are on the right side. I have heard that people have managed without but I have no experience myself.

[stevejgreen]

Re: starter motor swap

That is a very nasty hole. Did you find why it happened?

Don is very close to the answer.
An inertia starter motor moves its small gear into engagement with the large ring gear from the clutch side of the flywheel.
A pre engaged starter moves its small gear from the engine side.

The ring gear, mounted on the flywheel, is positioned one way around, or the other, as its edge is designed to help the starter gear to engage, from one direction or the other.

Ideally you would swap the flywheel with the right one as changing a ring gear needs heating as it is shrunk onto the flywheel.
It must be easier to change the wiring unless you plan to separate engine and gearbox to replace the clutch.

As far as I remember, both Marina starters have the same number of teeth, so either will engage with the ring gear. But both gears will wear more quickly if they are not matched correctly. Less wear should occur using an incorrectly matched pre engaged starter as the gears are not spinning when they engage.
I had a similar problem on a Ford many years ago.

[Pierre_Smits]

Re: starter motor swap

Thanks Don and Steve!
I guess it's better to change electronics a bit then.
This implies I guess the next:
1 remove starter relay because not needed anymore.
2)new conjunction for all the cables connceted to 12V (at) current relay? (now about 4 or 6 cables connected to relay (at)12V continuously) What about just connecting the ends formerly to the relay and put it in a black box?
3) 12V thick cable for pre-engaged starter motor direct to 12V battery +.
4) switch cable from ignition key needs to be connected to connection on top of pre-engaged? probaly I need to make the cable longer that formerly went to relay?
Anything else?

[Pierre_Smits]

Re: starter motor swap

why the piston rod broke I do not know yet. I will open up further when I'm finished with reinstalling the Marlin.
probably the engine failed in cooling in that spot or the bearing was broken first/already. However, the engine sounded fine just before breakdown.

[stevejgreen]

Re: starter motor swap

It might be easier to cheat a little.

Leave the relay in position.
Run a new large 12V lead from the old relay battery connection to the battery terminal on the new starter motor. You might be able to reuse the existing one?

Then run a lead from the old starter solenoid ignition switch terminal to the ignition switch terminal on the new starter motor

Only two wires to connect and everything else can stay the same.

The old starter relay will still operate but will do nothing apart from act as a terminal block.

[Pierre_Smits]

Re: starter motor swap

Thanks Steve,
that will work indeed. The old large 12V lead I attached to the pre-engaged and this will work fine.
On top of the starter motor (solenoid) I see 2 terminals but only 1 cable goes from the ignition switch to the relay. Should I connect this one also to the startermotor solenoid? Specifically the terminal closest to the engine and leave the other terminal blank? or is this an extra ground connection that needs to be connected?
thanks

[stevejgreen]

Re: starter motor swap

Sorry Pierre, that is one thing that I cannot be sure of.
Are there any markings on the solenoid that will give a clue.
You should not need an extra ground connection.
I take it that you can not check from the wiring on the donor car.

Perhaps someone else will be along soon who can help.

[lil_red_roadster]

Re: starter motor swap

Where the pre-engaged was fitted as standard (to a MK1 Marina) there is a red/white wire from the ignition switch going to a tag on the solenoid. Directly on the back of the solenoid goes the battery cable, alternator feed (thick brown) and a (also thick brown) takeoff for the live to fuse box...the latter two usually go on tags which fit over the main battery feed screw terminal. That's it...no relays, nada...brutally simple.