Decarbed w/ Seafoam...what happened???

Rebuilt carbs the other day and got the motor running good ( 1986 Prov 150). Decided to do a shock treatment because in the 4 years I've owned the boat , it's never been done.Compression was also low so I thought it might improve it. Now....did the shock treatment ( 16 ozs. Seafoam, 3/4 gal. gas, 2 ozs. oil) ran 15 mins. at 1000 rpms, turned off 15 mins. , til all was gone. Hooked back up to gas tank and ran for 15 mins. but now it runs like crap. Has an intermitten miss at idle, spits and sputters when I rev it up. Checked the plugs and they don't look fouled. Checked compression while I had them out and it was slightly less than before shock treatment.First question is.. should the compression read lower now that the engine is at operating temp. compared to cold readings before, and second question is why would it be running so rough now? It acts like it did before I cleaned the carbs almost. I don't suspect a carb problem. Could it be carbon that was dislodged causing a problem somewhere? This one's really got me scratching my head. Any help would be gretly appreciated.

If I had to guess it sounds like the carbs to me. Maybe something was in the fuel ****tail that got stuck in the carbs or Seafoam could have knocked something loose that has now clogged a carb.

[boats.net]

Warm compression reading will be different from cold reading. Could very well have fouled spark plug or dislodged dried gas in carb and need to be cleaned again.

Thanks for the help guys. I guess I'll redo the carbs again...was hoping to avoid that. I wonder if the fuel pumps could have been holding the same crud that the bowls had in them. Maybe I will replace fuel pumps at same time. It's been a few years on these pumps. Thanks again for the help.

Rebuilt carbs again. Rebuilt fuel pumps too. They had that same crap in them that the carbs did. Also put in new plugs. Boat runs great now. Idles great, gets on plane in 2-3 seconds and runs 5300 rpm ( operating range is 4500 - 5500). I can't tell you how much I hate ethanol!! Thanks for all who helped me on here.

[Tucker]

Gettin' ready to do the same thing only I got a 99 150HP with EFI. Do you think the long term approach, 1-oz/gal, would have the same results in the long run. Sounds like a PIA job to do with the boat in the water.

low power

i have a 70 hp Yamaha 3 stroke has low power. i pull the bottom spark plug and it was wet. i had a compression done and it was good.wend i put it in the water has low power and it cuts off but stars right up and go. i put new plug and still has low power but stay on don't cut off. can it be coil pack,need help

low power

i have a 70 hp Yamaha 3 stroke has low power. i pull the bottom spark plug and it was wet. i had a compression done and it was good.wend i put it in the water has low power and it cuts off but stars right up and go. i put new plug and still has low power but stay on don't cut off. can it be coil pack,need help

i have a 70 hp Yamaha 3 stroke has low power. i pull the bottom spark plug and it was wet. i had a compression done and it was good.wend i put it in the water has low power and it cuts off but stars right up and go. i put new plug and still has low power but stay on don't cut off. can it be coil pack,need help

Going through same thing with a 40 now. Spent nearly $100 on coil pack (as I was convinced that was it) now I am focusing on carbs tomorrow AM.