2000 80 Hp. 4 Stroke Yamaha

[x1957x]

Going to ask what this problem is. Last year I had an issue with it missing off and on and having issues with it accelerating. I thought bad gas. So I put in 10 gallons and ran half way decent but started again. I did change the online fuel filter also. Should a guy run nonoxygenated at like 91 octane in this four stroke to get a better performance? I have always ran regular gas in it but was told by someone to try the 91 octane stuff. Being a four stroke I was thinking maybe not. Maybe just a good tune up. I havent had it tuned up in 4-6 years though.  I live in Southwest mn. and is there a good tune up shop around? Otherwise off to South Dakota or Iowa. Any suggestions is greatly appreciated. 

[delcecchi]

I don't know if it really makes a difference, but I always burn 91 non-oxy gas.   And fresh gas does make a difference.  

 

You might start with putting new plugs in it.    Along with fresh gas, it might make a real difference.   

[x1957x]

Thanks Delcecchi? Just looking for some ideas....

[delcecchi]

If you stored it with regular in it, even with stabil, it's worth dumping the old gas in a vehicle, a few gallons at a time, and putting all new non-oxy in.  And a set of plugs.  Whole mess shouldn't be 50 bucks, and you have eliminated the first couple potential issues.  

[BIGFISH.JZ]

Ditto... I have 1001 reasons to never run anything but 91 non oxy in any small engine. I have 2002 reasons for using ONLY 91octane non oxygenated non ethanol premium in your Carbureted Yamaha 4 stroke outboard. I've been a fixing/rigging yamaha outboards for 20 years. If you want more reasons just search "phase separation". 

NOBODY SAVES MONEY BUYING THE CHEAP GAS FOR THEIR BOAT! Drain and mop out tank and replace all fuel filters. Then use the good gas. Carbs may be need a thorough ultrasonic cleaning from the dump gas already.

Edited March 28, 2019 by BIGFISH.JZ
Carbs

[x1957x]

Thanks guys!!! I have a 18.5'     ,, 2001 Lund Pro V with a 80  horse 4 stroke tiller on it. Is there a way to get the old gas out of the tank without using a pump of some type?

Edited March 28, 2019 by x1957x

[BIGFISH.JZ]

It should siphon thru fuel hose assembly. May have to add length to get below the boat floor.

Edited March 28, 2019 by BIGFISH.JZ

[BIGFISH.JZ]

I would remove a floor panel if the sender isn't accessible and pull the sender out. Make a 'rag on a stick' and mop it dry.... But that's just me....

Siphoning at the correct angle will get most of it. If it has an antisiphon valve (most outboards don't) you can pump it out with the primer bulb slowly... Worst case, remove sender to siphon directly, then mop it. 

Or.... Use a pump

 

[x1957x]

Ill try that bigfish and let you know how it turns out. Thanks

[x1957x]

Finally got a chance to reply. Thanks bigfish and others. Drained all the gas and filled with 91 octane, and changed the plugs. Runs the best it has in years!

[x1957x]

To all the, (2001 Yamaha 80 hp. 4 stroke on a 18.6 Lund ) guru"s out there. New thing with my motor.... If I take it out with 3 guys in it that weigh 250 each appx... I leave the boat landing and get it on plane and up to like 29-30 mph and 5200 rpm's. After awhile,,  like a 15 minute ride across the lake I go to a stop and the alarm goes off and I see like heat smoke coming out of the back of motor. If I put it in neutral and rev it up a couple times the smoke and alarm quits and it is good to go all day like trolling etc. I did put a new water pump and impeller in it last year also. I have not changed the thermostat in maybe 5 years either.  YEA I NKOW >>> Every couple hundred hours down here in the s.w. part of minnesota. Yes, the lakes are shallow and green and muddy all the time. I'm leaning towards the thermostat this weekend. Any ideas are appreciated. Thanks guys and gal's.

[delcecchi]

Couple of guesses... thermostat, like you saisd. Also, could there just be a build up of crud in the cooling system that could be flashed out somehow?  Like does this motor have one of those hose hookup things?

Finally, how sure are you that you didn't forget to replace something when doing the impeller or messed up somehow?