Can't get past half throttle.... :)

I have a 1984 Mercury 75 hp 4 cyl. Bought this boat as a project and I am learning. It runs fine at idle. In gear it gets up to about half throttle and starts to bog down. By covering the air intake on the top carb it starts to gain rpm. I am no mechanic but here is what has been done. Stator has tested fine on the ohm test. The timing was a bit off and I think that the person before me thought they may have been adjusting the idle when in reality they were adjusting the spark advance. I could not get the required 23 for the max timing so to the screw being bottomed out, no more room to go. It is floating around 27 BTDC. Could this be because i can't achieve the proper rpm? I found out today that the person that rebuilt the top carb never took the core plugs out. I did clean a spider out of the needle and am wondering if there is a way a part of it got logged up in their somehow? The second issue is that I would adjust the idle mixture screw on the carb and it would not respond the way the service manual said. Two three turns and nothing. I would lightly bottom out and it would start to bog down and I tried many times slow, fast, half way in-between and it was not responsive. Any information would be greatly appreciated again. I have rebuild the fuel pump, replaced all gas lines and filter.

Re: Can't get past full throttle....

27 is WORSE than 23! You're way over advanced. Back off the timing.

Jeff

PS: Does the carbs on that motor have long bolts that hthem tem on?

Re: Can't get past full throttle....

Yes the bolts are long that hold the two carbs on the motor. I have run out of room for adjustments on the timing and will be looking to see if I can find some room so I can get the required timing. Also I am going to replace the welch plugs this morning.

Re: Can't get past full throttle....

Thought so on those carbs. I had an identical problem with a set of those on my 70 Merc and it was a clogged fuel passage in the carb bowl. Remove the bowl and clean the tiny passage in it that's going down from above. Blow it out good with compressed air.

On the timing problem (which I now understand) I hope someone didn't remove the bolts in your flywheel and put it back on in the wrong orientation. (Don't ask!) You can determine this by finding TDC with a screwdriver: Pull #1 plug and rotate the flywheel until the piston is all the way up, then see it the pointer is on TDC.

Jeff

PS: Is that timing pointer adjustable (like on triples)? If so, IT may simply be off. You can rough align it using the method I described above. If it is, let me know and I'll walk you through aligning it more accurately.