'98 Yamaha 225 S/W chops revs down to 3k after 30 secs @ 5200

[frappples]

Engine runs great @ part throttle. After 30 seconds @ 5200 it dies down to 3000 for 5 seconds and then runs right back up. It will run all day @ 4500.<br /><br />Boat has twins. I've swapped everything; O2 sensors, oil level sensors, thermo switches, fuel pumps + vapor separators, coolant senders,and fuel pump resistors with no change.<br /><br />Any reccomendations?

 

[hondon]

Re: '98 Yamaha 225 S/W chops revs down to 3k after 30 secs @ 5200

Are both these engines running on a common fuel source i.e both running off the same tank,both off the same water separator?If so ,these are big girls that need alot of food.Maybe they ain't getting enough.

 

[frappples]

Re: '98 Yamaha 225 S/W chops revs down to 3k after 30 secs @ 5200

Thanks Hondon,<br />different tanks, just replumbed fuel lines w/ all 3/8ths hose and fittings and changed filters.<br />No Luck.<br /><br />The small fuel filter can next to the engine has fuel in it while the problem happens, so I don't think its the fuel feed. Even though it seems that way.<br /><br />I haven't had good enough seas to test with a five gallon tank and a hose because the boat's doing forty knots at the time.<br /><br />I also can't get up the balls to stand on the swim deck and watch a spark tester during the problem.<br /><br />Does a Yamaha rev limiter act like this when it cuts out?<br /><br />I also read something in one of the posts about a second stage current level for the fuel pump that kicks in @ high rpms. Know anything about testing this?<br /><br />the voltage across the fuel pump goes from 12.5 to 14 when the engine cuts down???<br /><br />The alarm does not sound when this happens.

 

[Bsalesi]

Re: '98 Yamaha 225 S/W chops revs down to 3k after 30 secs @ 5200

New to forum, was wandering through and saw your problem, I have a pair of 97 Yamahas (Saltwater Series) and I had the same problem for a year so I was curious if you got it fixed and what you found. In my case, the dealer did much the same as you, cleaned carbs, or at least charged me for it, removed anti-syphon valves from the fuel tank, replace hoses, fuel primer bulbs, etc. I called Yamaha in California and complained a little and they sent one of their own techs to the dealership to work on the engine. Here is what he found.... There was a small piece of aluminum shaving from the manufacturing process taht was wedged in one of the jets. It would sporadically move around in the jet and kill high speed operation just as you described. It seemed to run ok up to about 3.5-4k rpm and that was when the problem would kick in as the aluminum got sucked up with the higher flow rate. Anyhow, problem fixed and the engine has run smotthly since (both of em). Now, I'm hoping that you have carbs and not injection and this may help. Anyhow, if it was something else, let me know.