I have one either side of the filter. I was having problems getting fuel back into the filter from the tank when I'd change or drain the filter (airlock). Didn't want it to happen offshore so I put a slug in to prime the filter.

I would put the primer between the tank and first filter. My reason for this is, if there is a leak on any seals fittings hose clamps etc., by pressurising the fuel line those leaks could be seen. By putting the primer bulb ahead of the filter, you could have an air leak that goes un noticed.
Another reason is that a newly changed filter can be easily purged of air.

Well thats got me stuffed, was wondering if I put it after will it suck the fuel through the filter easily enough and if I put it before will it push it through to the motor. - Or do I just put two in!!

New lines going in with good clamps so leaks should not be a problem but never know in the future.

Cheers Guys

The suction line on a pump should have the least restrictions and be as sort as possible. The reason for this is that when a negative pressure is created, the more volatile components of the fuel can boil. This can create vapour locks. Car manufactures are putting the engine fuel pump in the fuel tank so the is no suction line.
Any restriction that is added to the suction line, fittings, primer bulbs, small diameter pipes and hoses and filters will add restrictions and cause a lower pressure. In other words a boat fuel system is a shit design at its best, and the engine mounted fuel pump really has a tough job to do, there is also a vapour separator at the motor to get rid of the vapour.
So one primer bulb, and if the filter water separator that you install has a micron rating of more than the fuel filter mounted on the motor, I would take out the motor filter as well, its not doing anything.

Cheers for all the info.

Filter is 10 microns and up to 190L per hour flow rate so hell of a lot more than the motor will need (Yammy F70A).

Using 10mm hose. Will put the primer before the filter and keep hoses as short as practical.

Will leave the filter on the motor mainly due to possible warranty concerns if removed (don't believe it is an in line filter so would have to block /reroute lines anyway).

Thanks again
Paul

Mean't to say, if your motor is under warranty, don't remove the engine filter. But you get the point that if the engine filter is courser than the filter you have installed, it really isn't doing anything. But because its a boat we're stuck with the long suction hose.