2000 - Yamaha 90 hp 2 stroke

[okeechobee]

I just purchased a boat that came with a Yamaha 90hp 2 stroke engine. The motor runs great at full throttle (anything over 3200rpm) but from 2000 to 3000 rpm it feels like it is missing out or fouled plugs and it will not idle. At low speeds and idle it just dies which makes it very tough to load and unload. I do not have an owners manual. The manual that the seller gave me is for OMC's in general. Does anyone have any idea what could be causing this problem? The boat had a new what pump installed last year. I do not know how the motor has been serviced in the past. I am the third owner.

[ausnoelm]

Sounds like some very basic troubleshooting first off, and get a genuine manual for your motor. Remove the plugs and have a good look at them, are they all the same, put new ones in anyway of the correct type and gap, run it off a remote tank and hose with fresh fuel, and when your manual arrives, look at the carbs.

[robert graham]

Same motor as mine....your carburetors may be due for removal and cleaning....a Yamaha dealer should be able to do it for about $200....then install a fuel/water separator and start using a fuel stabilizer like Stabil all the time in your gas tank. Learn to drain each carb float chamber a cole of times per year...an easy 10 minute job. These items should pretty much eliminate fuel related problems going forward...and these motors are nearly bullet-proof otherwise.

[throrope]

I spent more than $200. I gave it a go myself without success, but my real problem was contminated gas and a fouled tank. Unknowingly, I undid my work with the first start.

Now I empty the boat of all fuel and leave my right sized 12 gallon tank open and upsidedown to evaporate anything left between trips.

After seeing a buddy's two year old fuel line give up the ghost, this year I'm installing soft anealed copper tubing with short lengths of fuel line at the tank and motor. From here out it'll be a ten minute ten buck job every spring to eliminate fuel hose issues.

[ausnoelm]

Not too sure why you would bother with copper fuel lines, just proper certified fuel line will be OK.

[robert graham]

Not too sure why you would bother with copper fuel lines, just proper certified fuel line will be OK.

Yep, my 1999 Yamaha C90 has all the original Yamaha fuel lines...no problems so far!....

[Robertkelly]

Had similair problem with my 70 2 stroke, sprayneedle in 2e carb was blocked, did you got it fixed yet?

[99yam40]

Before you spread this info around it would be good to find the proper name of what was plugged.
Never heard of a sprayneedle.
maybe a main jet?

[throrope]

Not too sure why you would bother with copper fuel lines, just proper certified fuel line will be OK.

My buddy had the certified fuel line. Most have an inner liner that is the business end of ethanol resistant. His completely delaminated. The liner pulled out of the hose nearly intact. He humbly updated his thread endorsing the hose with pictures of its failure.

I have the same stuff from a well known name brand who I will not reference because I have other products from them in service and performing well.

As to the certification, most reference the 10% ethanol you get at the pump. Due to alcohol's affinity to water, phase separation, when ethanol falls out of the gasoline, is not uncommon and consequently, those materials rated for 10% get bathed in potentially 90% alcohol for the off season.

Every boat related forum I've visited is filled with threads on fuel system issues. The stuff clogging systems must come from somewhere.

I like letting all do what works and like making my own mistakes.

BTW - copper is half the price of certified hose and on my boat easier to install.

[okeechobee]

Sounds like some very basic troubleshooting first off, and get a genuine manual for your motor. Remove the plugs and have a good look at them, are they all the same, put new ones in anyway of the correct type and gap, run it off a remote tank and hose with fresh fuel, and when your manual arrives, look at the carbs.

Thanks, I am away from home this weekend but will work on lines, plugs and fresh gas when I get home. Any advise on mixing the gas and oil?

[okeechobee]

Same motor as mine....your carburetors may be due for removal and cleaning....a Yamaha dealer should be able to do it for about $200....then install a fuel/water separator and start using a fuel stabilizer like Stabil all the time in your gas tank. Learn to drain each carb float chamber a cole of times per year...an easy 10 minute job. These items should pretty much eliminate fuel related problems going forward...and these motors are nearly bullet-proof otherwise.

Thank you for your response. The person I purchased the boat from had work done on the motor but it obviously did not get it fixed. He suggested I use the emergency starting system but the manual indicates that if you have to use this switch I need to take it to a Yamaha service dealer? any thoughts on this?

[okeechobee]

Had similair problem with my 70 2 stroke, sprayneedle in 2e carb was blocked, did you got it fixed yet?

Not fixed yet but plan on working on it as soon as I get home.

[okeechobee]

Before you spread this info around it would be good to find the proper name of what was plugged.
Never heard of a sprayneedle.
maybe a main jet?

Any chance this is an electrical problem?

[okeechobee]

Had similair problem with my 70 2 stroke, sprayneedle in 2e carb was blocked, did you got it fixed yet?

Did yours run great at high speeds?

[okeechobee]

Sounds like some very basic troubleshooting first off, and get a genuine manual for your motor. Remove the plugs and have a good look at them, are they all the same, put new ones in anyway of the correct type and gap, run it off a remote tank and hose with fresh fuel, and when your manual arrives, look at the carbs.

Thanks. I have located a manual.