Recommendation '89 Yamaha 90HP Idle Problem

[sc_shane]

Hey guys. I took my 1989 Yamaha 90 horse out 3 weeks ago to start the season off right. Everything worked like a charm, and the ole girl ran like a champ, with the final cruise for the day lasting about 1.5 hours of solid cruising. On the way back to the dock, when I attempted to go to neutral, then reverse, she cut off on me. That was kinda fun scaring the crap out of everyone when I banged the dock real good. Then, I was doing the same, putting her on the trailer, and she shut off on me again. I threw some Sea Foam in the tank with fresh fuel to go out last weekend, but the ole girl ran like crap at idle speed. Also, on low RPM, just starting off, she seemed to run bad too.

I'm planning on doing 2 things to see if it helps. First, I'm going to change the fuel line. The old one looks just that - old. I had already ordered and just got the replacement in today. Nice and brand new! Next, I'm going to replace the spark plugs, but I'm not sure what plugs to buy or what gap to gap them. Any recommendations? After that, I may attempt to rebuild the carbs, but I've never done anything like that before. I'm not a mechanic, but I did just change the water pump on my Dodge Durango, and swap an alternator on my wife's Chevy Tahoe. I tinker, but usually know when it's too much for me and just pay someone who does.

What do you guys think? Recommendations on plugs? Should I replace the wires while I'm at it? I ordered a manual (real Yamaha service manual, not Sealoc) and I won't be doing any work till it arrives anyway, but thought I'd ask you pros! Thanks, guys, in advance!

 

[Ray Neudecker]

Re: Recommendation '89 Yamaha 90HP Idle Problem

NGK B7 HS-10 is the correct plug. after replacing, check for fire on all three cylinders.

 

[Marc III]

Re: Recommendation '89 Yamaha 90HP Idle Problem

The NGK B-8HS10 is what my '88 model 90 horse calls for, gapped @ .035-.039". NAPA has them in stock. Check your fuel filter too. If it's like mine it can be removed and cleaned. I cleaned my carbs two weeks ago. They are a piece of cake. No kits needed. The idle circuit is on the top of each. My idle jets were set at two rounds out. I'd be willing to help if you like. The wires are made onto the coils and would likely outlast them. My wires nearly worked themselves off the plugs, I secured them with wire ties.

 

[sc_shane]

Re: Recommendation '89 Yamaha 90HP Idle Problem

Thanks Marc & Ray. I'm going to replace the fuel line and spark plugs tomorrow. While I'm at it, I'm going to see if I can take a look at that fuel filter. I took a look at the diagram on yamaha-motor.com and it looks like something I should be able to handle. I really appreciate the offer Marc! I may take you up on it. Have you done any fishing? We were up on the Westminster leg the 1st weekend of May (the last big rain we had) and tore up some blue gill up at the farthest north point we could go. Can't wait to get back!

 

[Marc III]

Re: Recommendation '89 Yamaha 90HP Idle Problem

I haven't been fishing. Planning to go Monday though. I left you a PM also.

 

[Marc III]

Re: Recommendation '89 Yamaha 90HP Idle Problem

Did you get her running better?

 

[sc_shane]

Re: Recommendation '89 Yamaha 90HP Idle Problem

Still haven't made it out to work on her yet! UGH! Work sent me to Utah for a few days and we had vacation set last week. Heading to the storage unit Friday to work on it. After I get done with the few things I'm going to do, I'll dump it in the water and see what happens. If it's no good, I'll probably bring it home and work on it this weekend (the wife wants to hit the lake Sunday!). Wish me luck!