90hp Yamaha 2-strock

[plus+]

Hello all,

I did search for a solution for the problem with my 90hp Yamaha 2-strock 1994 model which started to idle hard, smoke little more and will quite if left idling. The acceleration top end speed same as before, but in the midrange speed it will slow little and get back to the same speed again. It looks like some thing holding it!
What would be the problem? The fuel pump, filters and lines are clean and working fine. Spark plugs look fine too.

Thank you all for any help.

Best regard's
Plus+

 

[plus+]

Re: 90hp Yamaha 2-strock

Can i get some help here??

 

[JB]

Re: 90hp Yamaha 2-strock

Sounds like a carb problem, plus. Probabaly idling on only 2 cylinders.

 

[Ray Neudecker]

Re: 90hp Yamaha 2-strock

Sounds like a fuel restriction from a bad fuel pump or blockage in the carbs.

 

[plus+]

Re: 90hp Yamaha 2-strock

I did check for sparks on each cylinder and all of them have a spark when I pull the spark plug wire, and will try to see if there is any problem with the fuel system.

 

[plus+]

Re: 90hp Yamaha 2-strock

by the way, how to check if the fuel pump working right?

 

[plus+]

Re: 90hp Yamaha 2-strock

Thanks for the reply JB and Ray Neudecker

 

[plus+]

Re: 90hp Yamaha 2-strock

i did change spark plugs and fule pump, now it will idle okay,but i lost the speed and the boat will not get on plane!!

 

[mikesea]

Re: 90hp Yamaha 2-strock

You could try pulling off plug wires off,one at a time and see which cyl.isnt firing,of course you get spark,but probably no fuel on one cyl. I'll guess the bottom.It will also be getting oil,which wopuld make sense for the excessive smoke ,and with new unfouled plugs it idles better,but no performance. If the boat sat for a long period I would bet big on dirty carbs. Take em off and clean all ,including filters too.

 

[plus+]

Re: 90hp Yamaha 2-strock

You could try pulling off plug wires off,one at a time and see which cyl.isnt firing,of course you get spark,but probably no fuel on one cyl. I'll guess the bottom.It will also be getting oil,which wopuld make sense for the excessive smoke ,and with new unfouled plugs it idles better,but no performance. If the boat sat for a long period I would bet big on dirty carbs. Take em off and clean all ,including filters too.

I did pull the plug weirs off one by one, the middle one did not make any change to the engine while idling, so I took off the crabs and cleaned them "did not see any dirt " and tested the boat, idled okay, but the boat will not get on plane?!!

 

[Ray Neudecker]

Re: 90hp Yamaha 2-strock

Buy or borrow a timing light to confirm fire on all three cylinders.

 

[karlster]

Re: 90hp Yamaha 2-strock

You could try pulling off plug wires off,one at a time and see which cyl.isnt firing,of course you get spark,but probably no fuel on one cyl. I'll guess the bottom.It will also be getting oil,which wopuld make sense for the excessive smoke ,and with new unfouled plugs it idles better,but no performance. If the boat sat for a long period I would bet big on dirty carbs. Take em off and clean all ,including filters too.

I did pull the plug weirs off one by one, the middle one did not make any change to the engine while idling, so I took off the crabs and cleaned them "did not see any dirt " and tested the boat, idled okay, but the boat will not get on plane?!!

When you say you cleaned them it is hard to know how thorough you were in cleaning every orifice and passage. I learned the hard way that there are a lot of well concealed passages and components that can conceal gunk or varnish that will severely compromise engine operation.

When you take the carb apart look at it logically and figure out the path the fuel and or air must follow to enter and exit the carb. Run a fine wire or spray carb cleaner (or compressed air) through each orifice and passage. It is hard to find wire small enough sometimes. I pull one strand out of a wire wheel or wire brush. It is nice and stiff yet very thin.

Since you are now idling ok it sounds like the main jet and related passages are the area to scrutinize more closely.

Don't forget to synchronize your carbs after you finish cleaning and reassembly.

Good luck
Karl

 

[plus+]

Re: 90hp Yamaha 2-strock

can you tell me how to synchronize carbs?
this is my first time to do a carbs cleaning ever..

best regard's