130hp motor shakes at 1800rpm and won't go over 2000rpm

[Yamaha130hp]

I have a Yamaha 130hp 2-Stroke and it was running great until this weekend. I was pulling the kids on the tube and all of a sudden the power diminished to the point where I could only go about 5mph and the rpm's maxed out at 2000. It starts up fine and seems to run fine in forward and reverse as long as the rpm's are 1700 or less. As soon as it hits 1800rpm it begins to shake and it won't go any faster. I can get the rpm's up to 2000 at most. The plugs are good. The fuel filter is good. Put fresh gas in it. Any ideas what might be the issue here?

Thanks!

[throrope]

Not enough info to provide a smoking gun.

Since this came suddenly, I suspect the shaking is from one or more cylinders not firing. That also explains the loss of power & rpm's. If your outboard is similar vintage to our TLRD90, it should fall under the old "spark or gas" diagnosis.

Spark plugs are easy to check and high voltage shorts should show arcing at night.

I'd then try one plug at a time listening for the one(s) that don't make a difference. Then open the carburetor serving that cylinder. If you find crap, go through all of them, renew gaskets, replace the fuel lines from tank to engine, install a 10 micron water separating filter if you don't have one and check the on engine fuel lines for degradation. Not a insurmountable job, with time, care and a six, can be done without breaking stuff. Since this often gets done half a$$ed by service providers, I recommend DIY.

At the risk of preaching to the prior, this is a common issue with pre-ethanol materials. 100% gasoline leaves a varnish. Ethanol desolves the varnish and any rubber parts not formulated to resist it get eaten. The debris gets carried to the carbs and does a great job clogging them.

[jb123]

does your alarm system work ?? sounds like your either overheating or low oil

[Yamaha130hp]

I just took it out on the lake and pulled each plug one by one and they all seemed to be working as expected. I don't know enough about carbs to start taking them apart to look for debris inside of them or anything. I checked the oil and it's 3/4 full. I tried some seafoam and that didn't seem to make any difference either. I took a close look at the gas lines and they don't look like they are corroded or anything like that. Nothing else really jumps out at me. Is there anything else I can try myself or is this the point I should take it to someone who can dig into the carbs?

[Yamaha130hp]

Alright, I took it into the shop and they found out that the wiring harness had a short which was causing the motor to go into what he called, "rev limiter" mode. Basically the system thought the motor was overheating and it was limiting the rpm's to keep it from getting hot(ter). Even though it wasn't overheating or anything. Who would have thought!?