The timing is correct?? Is it supposed to be 10 or 13 initial?

Understand you set the idle at max vacuum but I would still try adding a little fuel with the idle screws. Eddie is right the motors are probably too lean at idle if the timing is correct. BTW where did you measure the vacuum, above or below the blower?

Ok, I know some won't agree with this, If it were mine I would can the merc dist, run a mallory unilite or campairable stand alone dist, lock the timing curve and run about 28 deg, they will start fine with the low compression and the higher initial timing will clean the idle up and make the boat much easier to handle a docking speeds....this set up is what weiand recomends on their blower set-ups...Rob

They should idle at easily at 750-800rpms in neutral and not stall when put in gear. 950 rpms is way too high and you might even be getting a little advance from the module. If you have TB IV ignitions, the base timing should be set at 13*to get 35* total. The early 525sc used an older merc ignition with a slightly different curve. I don't know the specifics numbers on that one.

You need to get an adjustable timing light and set them on total timing. Initial timing is what it is. Every module is a little different in the amount of advance it has. They also will vary a little at which rpm they come in. So, ignore initial timing. Only use it as a reference to know you are close and set total advance.
Eddie

Thanks fro the help Don we ended up stripping the carbs right down and blowing out all the jets, re-setting the float height, vacuum and timing and it now behaves as it should, I think the boat has been standing a long while before we aquired it and the fuel had gone off more than we thought.

Thanks to all the guys who took the trouble to reply to try and help us out I think the main trouble was this boat has been standing for a while before we aquired it and the fuel quality was not good, we ended up stripping the carbs right down and blowing out all the jets, cleaning out the float chambers, resetting the float height, mixture screws and timing, this seems to have cured the problem as the boat now behaves in an acceptable manner for what we have.

Thanks again guys and I hope you all have a good Xmas.

Sounds good, I thought in your first post you said you rebuilt them. Had to do it again? Well glad it worked out.
Merry Christmas

FYI. IF the balancer is stock, it is probably marked for 35 deg timing-mine is. If you have mostly stock engines and ignitions, you will be better off running with all the advance (35 total) because it comes in late and will make your exhaust valves last longer. My boat had high leakdown through the exhaust when it was checked at less than 160 hours and I believe it was because the marina/previous owner thought they would "rethink" Merc Racings timing spec and run less timing.

My 525sc had a 35* timing mark filed into the balancer as well.

My only question is why merc is running 35 total, thats a ton on a blower motor..wieand who makes the set-up says keep to 26 total max ??