93' Yamaha 70 dies

[iwannagofish]

I just got my first boat, so I'm at your mercy. One of the problems is, with the prop in the water, when the prop engages while throttling up the motor dies. I can trim it up to where the prop is half out of the water and it engages fine, then I trim down to operate.

My second problem is it seems to run slow. I open the throttle all the way without satisfaction. I don't have anyway to tell how fast I'm going, but I know I should be going at least twice as fast. I have a friend that has a 75 hp that hauls a**. So, I know mine should be close to that. Anyway, any advice would be greatly appreciated.

 

[Dunaruna]

Re: 93' Yamaha 70 dies

Maybe we can help each other. I have the same motor and had a similar problem, it was gunk in the carbs, a rebuild fixed it. I would suggest that apart from regular service items (replace plugs, clean fuel filter screen, check for air leaks in the fuel system) carb rebuilding is a semi-regular service item, every 3 years or so. The carbs are quite simple in operation and you have the advantage of doing one at a time and using the other 2 for reference.

Do you have a manual?

Could I ask a favor of you please? I need to know what the oil level sender wires connect to at the dash (oil warning lights in the tach), my adapter harness is missing.

 

[iwannagofish]

Re: 93' Yamaha 70 dies

Thanks for the tip. I'll look into it as soon as I get home. I'll be more than happy to tell what the wires attach to in about 3 weeks. I just started my 3 week rotation offshore. To answer your other question, I did not recieve a manual with the motor. If I run across one online, I'll pass on the link. Thanks again.

 

[Dunaruna]

Re: 93' Yamaha 70 dies

I have a manual, I was asking if you needed one.

 

[JUSTINTIME]

Re: 93' Yamaha 70 dies

rebuild the carbs and replace the fuel pump

 

[iwannagofish]

Re: 93' Yamaha 70 dies

Dunaruna...my bad
Yeah, I could really use one. If you don't mind, could you tell me what the spark plug gap should be, the torque spec and if there is a better plug than NGK b8hs-10? Thanks again

 

[Dunaruna]

Re: 93' Yamaha 70 dies

The NGK B8HS-10 is a good plug. The torque setting is 18 ft lbs. The gap should be between .035 and .039 thou. .039 thou is equal to 1.0 mm, hence '10' in the part number.

You have a PM.