1987 Yamaha 200 hp losing power past 2,000 rpm

[welcraftv20man]

Hi,
Starting mid season last year my 1987 yamaha outboard has been losing power past 2,000 rpms. it idles fine but when pushed up near and past 2,000 it loses power. it does not entirely stall bt just will not pick up unless you manualy prime the bulb. i had to have my son pump the bulb to get us back in. I have changed the fuel pumps (both of them) even though there were no holes in the diaphrams. i changed the fuel line from the tank to the bulb and even the fuel lines that are associated with the pumps. I have also changed the 10 micron fuel/water seperator. (when i looked inside the old filter there was a lot of clumps that looked like breda crumbs or whaat not) also the fuel was a bright lime green. the primer bulb is only 2 years old. i am thinking i may have bad gas or the pick-up for the ful in the tank is very clogged and is starving the engine of fuel. the bigger filter was jam packed with crud and even the smaller filter on the engine had some debris in it. If you have any ideas as to what the problem is please let me know. i am getting desperate. i just wnt my boat to run smooth.
Thanks a lot in advance,
Dann

 

[yamatech43]

Re: 1987 Yamaha 200 hp losing power past 2,000 rpm

Clean everything out, including the fuel tank, don't run the motor on this 'fuel'....you will destroy a piston.....check the vent on tank, also the 'coast guard valve' is possibly sticking at pickup of tank. This causes high vacuum.....check the vacuum on line during running. Install vacuum gauge just befor engine's filter. Should be 2" of vac. or less at idle....never more than 4.5" at W.O.T.

 

[99yam40]

Re: 1987 Yamaha 200 hp losing power past 2,000 rpm

Checking fuel pressure and vacuum is a very good idea, and if you have that much crude in filters then you probably have it everywhere else, so clean it all well
Maybe just a coincidence but 2K is also where safe mode limits RPM.
Check to make sure the oil level and temp alarm system are functioning properly