1990 200hp Johnson GT idleing and WOT Problems

I was just wondering if anyone had any suggestions for me. For about the last 2 years my 200 hp johnson has not performed up to previous standards. I have a 1990 Stratos 201 Pro. At WOT, I only get about 5000rpms on guage and about 51mph on GPS. I used to be able to get 6500 rpms and about 65mph GPS. Also, the motor idles fine out of the water, but once in the water, you can barely keep it going at idle speeds. It runs better when on the plane but still not near the speed it had. This has been an ongoing problem for about 2 years. I have installed new plugs, a new coil, and a new power pack. I've also had a cylinder test run and I'm getting good compression on all six cylinders. The only thing I can think of that might help my problem is raising the motor up a little higher by adjusting the jackplate. Is it possible that it has slipped down a little and that's why I've noticed a decrease in performance? If anyone has any suggestions or maybe a different idea of what might be wrong, I would greatly appreciate it.

Thanks again.

Re: 1990 200hp Johnson GT idleing and WOT Problems

have you ever done a decarb, cleaned and rebuilt the carbs, considered you are carrying extra weight, as wet foam in the hull. it would have to slip down enough you would notice, scratch marks on the plate.

Re: 1990 200hp Johnson GT idleing and WOT Problems

tashasdaddy said:

have you ever done a decarb, cleaned and rebuilt the carbs, considered you are carrying extra weight, as wet foam in the hull. it would have to slip down enough you would notice, scratch marks on the plate.

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Thanks for the reply. I have used the decarb spray 2 times in the last 2 years and hasn't made a big difference. I've never had the carbs rebuilt but didn't think I would need to because the mechanics we've used said it's not in the carbs. They seem to believe it's in the firing system. I don't know what to believe anymore. I just know it's not up to par with how it used to be.

Thanks for the suggestions.

Re: 1990 200hp Johnson GT idleing and WOT Problems

If you use your boat a lot, 1 decarb a year simply isn't enough. Not only do you get carbon build-up in the cylinders, but in the exhaust as well. I'd do a serious decarbing with the 3-gal can method. Then, maybe once again.

Re: 1990 200hp Johnson GT idleing and WOT Problems

iwombat said:

If you use your boat a lot, 1 decarb a year simply isn't enough. Not only do you get carbon build-up in the cylinders, but in the exhaust as well. I'd do a serious decarbing with the 3-gal can method. Then, maybe once again.

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Thanks again for your advice. Could it also be the reverse situation? Actually last year I may have had the boat out 5 times total, and just last week was the first time this year, primarily because the motor's not running right and I didn't feel confident in using it regularly. I would just go with friends, but this year I've got the "itch" to go fishing again, and I'd like to use my boat. It's actually not been running well for the last several years and each year I used it less and less. I don't want to take it to a mechanic again unless I can get something resolved. Every time I've taken it, I was told what the problem probably was and each time it didn't help. I appreciate all the good suggestions I received here. I will keep searching for an answer and hopefully something good will turn up.

Thanks again

Re: 1990 200hp Johnson GT idleing and WOT Problems

Actually a good Decarb "SHOCK" treatment would be a very good thing. Also, I bet you have bad gas. You have been adding new fuel to bad gas for too long. I bet that after you do a good decarb, and get all fresh fuel in her she will run like she used to.