89 Yamaha 4 stroke 9.9 HP Problem

Discussion in 'Bubba's Outboards' started by BailBonds, Feb 6, 2008.

  1. BailBonds

    BailBonds New Member

    Messages:
    282
    State:
    Indiana
    Greetings fellow Cat nuts! I bought a pontoon last fall with a 1989 9.9 HP Yamaha 4 stroke (HP restrictions on lake). It starts easy, idles and motors up right away. After a few minutes at any throttle setting above an idle there is a distinctive CLICK like a relay and it idles down. Never dies just idles down and stays that way for 30 seconds or maybe a minute then it clicks again and back to the correct throttle. I've worked on a lot of motorcycles but this thing has me stumped. Primarily because it's an intermittent problem. Any ideas? Any help is appreciated. Rick in INDY
     
  2. BailBonds

    BailBonds New Member

    Messages:
    282
    State:
    Indiana
    Just an FYI for anyone with a similar problem. After much digging it appears this model (as do many others) has a low oil pressure SWITCH not sending unit. If the oil pressure drops to about 8psi it tells the CDI to slow it down to about 1,000rpm. The switch should be open at pressure and close at low pressure which grounds the wire thus telling the CDI to back down but lets you get home. So I'm guessing a bad switch or at worst a bad oil pump. But being an intermittent problem I'm thinking the oil pump is OK. I'll be swapping as soon as I get a break in the weather and post the results.
     

  3. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    Rick I thank you for posting your findings. If I had posted on your problem it would have been pure guess work on my part as I know very little about 4 strokes. I appericate you taking the time to post the findings.
     
  4. BailBonds

    BailBonds New Member

    Messages:
    282
    State:
    Indiana
    Update: I finally got this pontoon project back on the water. The problem turned out to be a clogged oil strainer. It's a 1" diameter wire mesh kinda oil filter. It was clogged with stuff solid. The oil had been changed but it looked like the filter/strainer had never been removed and cleaned. The oil pressure sensor did it's job and idled it down. A local outboard "mechanic" had told the guy I bought it from it needed a new engine. He just happened to have used one just like it. Thanks for the input!