idles like a dream, but wont accelerate

I have a 1988 Johnson 28 SPL. The motor was running fine but began to feel as if it was out of gas. Fuel tank was almost full. Checked all fuel lines, fuel pump filters and diaphrams, replaced spark plugs, did compression test (60-62 in both cylinders). Did find the jet in the carb had a small blockage and was cleared out. Motor was put in water and idles fine but will not accelerate. Any advice is greatly appreciated. 2 weeks left of duck season and no boat!!

Your compression sounds a little on the low side. Try another gauge and see what you get. Do a cyl drop test on it to see if it's running on both cyl's.

My gauge gave me about 62 on both and the mechanics gave 60 on both. He advised that the motor was junk and suddenly remembered he had an older used motor that he could sell.... He is not my normal mechanic but had to do on short notice. I am getting a new boat after the hunting season but I was trying to figure out if the motor is junk before I try to sell it....a friend is interested in the boat. I did just discover that the fuel line from the tank to the motor was not holding pressure so I replaced the ends to see if that makes a difference tomorrow.

Perhaps the low speed fuel mix adjustment is too lean.----That will cause it to stumble.---Try opening that up 1/2 turn.--------Were any adjustment made on the rod that goes to the carburetor from the tower shaft ??--------------Also verify that you have spark on both cylinders.-----------The low compression may also be a blown / leaking head gasket.

Thanks racerone for the assistance......i did not make any adjustments but I cant speak for the mechanic or anyone else. I am going to get it in the water tomorrow and try making adjustments. We did have to replace the head gasket in November due to a sheared off head bolt. We replaced all headbolts and the gasket while we had it apart. I am in the process of checking the spark on both cylinders now. I have read on the forums for 7/16" on spark. Will that apply to this motor as well? Thanks so much for the assistance. I will post later with my results.

Yes. 7/16" air gap.

Carburetor must open at the correct time.--------If it opens too early the motor will stall.------Was the cylinderhead refaced ??-----They all warp after years of service.

Well I have good news...the boat ran beter this morning. I got it in the water and made small adjustments and it started coming around. The rain came and I had to call it good for a while. I found last night that I had a bad clip from the tank to the fuel connector on the motor. Replaced those and it made it a lot better. It is still sluggish after 30-45 seconds at full throttle but comes around if throttled down and back up. I was wondering about the orifice screw. not sure how it works. I have it in pretty tight. does it need to be loosened to allow fuel to flow?

The high speed jet ( orifice ) just needs to be screwed into the float bowl till it is " snug "----------------The orifice has a calibrated hole to let the correct amount of fuel through.It must be clean and no adjustments needed.

Wanted to thank everyone for the help. I have the motor running to get me through the all important last few days of the season. I am going to continue to tinker with it, as I think you guys have me on the right track. It is running like it is just a few minor adjustments away from being better than before. My dad made the comment this morning that the boat didnt run this good when he bought it in 1992. Just need to get rid of the surge at full throttle that comes in after 2 minutes or so. I am able to run 3/4 throttle all day long and that is a great improvement from having to row all the way to the dock like last week. Thanks again to all!