What is Primary Pickup?

[karnage]

Earlier this year I picked up my first boat and have since been giving it hell, as my first forum post can show for some of it. The spark advance timing screw wiggling loose was the primary culprit for poor performance. I took the proper approach and purchased the proper factory service manual for my engine and tried to adjust the timing screws. Most of the stuff was still a little unclear as I'm very unknowledgeable but I was able to generally set my full throttle stop and got the spark advance to 11/16". Now, the engine gets up on plane very fast, does better on fuel, and even idles fair out of proper adjustment. But I don't believe the smallest of the screws, which I believe to be primary pickup, is properly adjusted. I have no real reason to believe something is wrong with it besides I had touched it and then put it back to about as I found it. I don't want to subliminally be doing damage to my motor, even though it runs great. So, enough with the story. I would just like to get a rough description of what primary pickup is and maybe of the other timing elements aswell. I couldn't find anything online in lamens terms about what it does, thanks.

 

[racerone]

I think you are referring to the point where throttle plates start to open.------A much mis-understood concept.

 

[karnage]

Maybe, I'm referring to the smallest screw among the bunch, between the arms. It is called primary pickup in my service manual.

 

[racerone]

Has to do with where throttle plates open.

 

[Dukedog]

you are on tha right path with "primary screw".. first make sure all butterflies are completly closed.. tha pirmary timin' screw is tha only thing moved to set your idle rpm/speed... tha real world way to set idle (primary) timing is as follows.. forget what book says for timin' numbers for idle.. put tha boat in tha water, start, put in gear, now set idle (primary) timin' to whatever rpm and/or speed both you and tha motor are happy..................... jmo

 

[karnage]

Okay, so that's fairly good news for me. My carb shutters are shut at idle and my hotfoot responds accordingly. I've previously adjusted the full throttle stop screw. Boat idles and runs alright, so I guess I should just leave it as is.

 

[Chris1956]

Primary pickup is a synchronization of the spark advance and the carb throttle plate. On the Merc V6 motors, the carbs should start to open when the timing is 4-9* ATDC. Max spark advance is 21*BTDC on those V6 Mercs.

You want to get these settings correct or you can damage the motor.

 

[Faztbullet]

Give yer carb roller about a 1/8" gap off cam, adjust pick em up timing to 1000rpm on hose and yer should be good..

 

[karnage]

Give yer carb roller about a 1/8" gap off cam, adjust pick em up timing to 1000rpm on hose and yer should be good..

This would be an easier adjustment and will note this.

Primary pickup is a synchronization of the spark advance and the carb throttle plate. On the Merc V6 motors, the carbs should start to open when the timing is 4-9* ATDC. Max spark advance is 21*BTDC on those V6 Mercs.

You want to get these settings correct or you can damage the motor.

This is more like the answer I was looking for. I'd like to set it properly and not have to worry about it anymore. I was able to generally set the spark advance based off of the 11/16" measurement between the arm and the block. Being an amateur and novice marine mechanic, timing stuff almost makes my head explode. I've done a lot of research this morning and have come to the conclusion I will pick up a timing light today and continue to learn and try to do this right.
My service manual says pick up should be set to 11°ATDC. I'll come back to this forum with updates and maybe for more help setting primary pickup, thanks for the responses.

 

[Chris1956]

You should also buy a caliper, so you can set the timing pointer correctly.

The sequence is to remove all spark plugs, and measure from top of #1 piston at TDC to cylinder head. Now add that measurement to .464 inches, and rotate the piston until the piston is recessed by that sum. Now adjust the timing pointer to the .464 mark on the flywheel. Now timing pointer is accurate.

Install #1 spark plug and wire. Attach timing light to #1 plug wire. Set ign on and jumper starter solenoid until motor cranks. Set boat throttle control to read primary pickup timing spec. Now adjust primary pickup set screw (not spark advance) until carbs are closed, but ready to open.

Now advance throttle full and crank motor. Set max spark advance set screw to allow spark advance max of 21*BTDC.

 

[karnage]

Update on my 84' blackmax's timing. I learned a lot yesterday and was able to do most of the steps in my service manual which I previously didn't understand.

Although I understand the results of an inaccurate timing cover, by looking at the piston head through cylinder 1 and looking at the decal and pointer, it appeared to be right at 0 after many rotations.

Started with setting the idle screw against the stop where the cam and max throttle screw boss have an eighth inch gap.

With the idle screw against the stop, turned over the engine and set the primary pickup to 11*ATDC with the timing light. This was set upwards of 20*ATDC before I adjusted it.

Then, with throttle cable still disconnected I put the spark advance screw to the stop and adjusted accordingly to a cranking speed of 18*BTDC. I don't remember what this was set to, but it was at least 10* off. Spark advance is 16*B.

I had previously synched my carbs and set max throttle screw to right when the shutters are fully open.

One thing I'd like to note is that once I connected the throttle cable and had my buddy open the throttle to let the spark advance screw hit the stop, there was about 1mm between the stop and the screw. Like wise with the idle screw. When he recessed the cable as much as possible, there was a very small gap which resulted in the primary pickup being a couple degrees before 11 sometimes. I could just wiggle the arms or push it against the stop and have it go back to spec.

I'm not too worried about it though, as the manual never told me to reinstall throttle cable and to get it to spec without the cable, and with screws to stops. The timing is a lot closer to spec than before.

We started it up to test it and the idle was high, right at 1000. The next step in the book is to get it out in the water and adjust the idle in forward gear before reconnecting the throttle cable with a hair of preload. So I'll loosen up that idle screw a bit to get it closer to the spec of 750 idle in forward gear.

Didn't wanna leave this thread on open end, I'd gladly hear any comments or concerns.

 

[Faztbullet]

1K on a hose is good....

 

[karnage]

1K on a hose is good....

Im not sure what 'on a hose' means but yeah I guess I wasn't thinking about neutral vs in gear. Idle rpm in forward gear is supposed to be 6-700. So, if all is well there I may not touch it.

 

[racerone]

On a hose ( muffs ) on a trailer you are not running with a load !!----In gear is still the same as neutral.-----Simply because the prop does not have any WORK to do moving air.

 

[karnage]

On a hose ( muffs ) on a trailer you are not running with a load !!----In gear is still the same as neutral.-----Simply because the prop does not have any WORK to do moving air.

Okay, understood. May or may not come back to this forum thread. I appreciate all the responses.