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Author Topic:   Yamaha cut off
Rick posted 02-10-2001 07:56 PM ET (US)   Profile for Rick   Send Email to Rick  
I'm new to power boating and recently purchased a 17 Montauk w/ 90 oil injected Yamaha. Ran like new until recently it started shutting off a WOT and real hard to restart. Have fuel to the clear plastic bowl in engine compartment. Would the fuel pump be this erratic to only cause a problem at WOT. If so, does the engine need to be at a specific rotation to remove and check it. Once the engines sits awhile, it runs fine until it is opened up for appx 30 sec and the dies again. Any help would be greatly appreciated. Thanks, Rick
triblet posted 02-10-2001 11:41 PM ET (US)     Profile for triblet  Send Email to triblet     
Any chance it it's got an automatic
shutoff if it gets too hot?


Clark Roberts posted 02-11-2001 07:57 AM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
Rick, you may have a high temp shutdown or simple fuel supply problem caused by a bad fuel pump, clogged filter, pinched line, debris in the pick-up tube in the tank...etc! Or it may be more serious, like carbon jacking (usually center cyl. on three cyl Yams, I know 'cause I,ve been there!). This condition consists of carbon build up behind the rings which "jacks" the rings outward, thus causing excess friction (exagerated by high temp of full throttle) which mechanically shuts down the engine while also removing metal from the cyl wall! Usually two or three shutdowns and the engine starts knocking on restart and it's all over.. rebuild time... I don't want to be the prophet of doom here, just imparting info! In any case, my suggestion would be to check the engine out throughly before you run it again... these things don't fix themselves..heh,heh.. You can check for carbon jacking by removing the plugs and visually inspecting the cyl walls... dealer's shop has a little fiberoptic light that slips inside...etc... This is a condition that is not always revealed by a compression check (unless cyl wall is so scored that compression is lost).. hopefully you don't have the above problem and it's a simple fuel suppy thing.. still important to get resolved before running again as fuel restriction can lead to instantaneous "lean-out" which can hole a piston, score cyl walls etc.. very , very quickly. When you get the problem solved, suggest that you treat that engine to a once a year (or twice a year if you use boat all year round) to a dose of Yamaha "Combustion Deposit Cleaner" or Merc "PowerTune"... follow directions on the can! This is some insurance against the Carbon Monster!!!! Also you can add Yamaha "Ring Free" in maintenance dosage to your gas all the time... More later if I can think of anything... Good luck and happy Whalin'.... Clark.. Spruce Creek Navy
triblet posted 02-11-2001 12:07 PM ET (US)     Profile for triblet  Send Email to triblet     
Clark: if carbon jacking, it would be hard
cranking on restart, right?

Rick: Is it hard to crank on restart, or
cranks well but doesn't fire?


Clark Roberts posted 02-11-2001 12:36 PM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
Chuck, not necessarily hard to restart as metal has been removed from cyl walls... but, it may be hard to crank over and/or just freeze up altogether! I had a brand new 1990 Yamaha Pro 50 with about 50 hrs on it and it just stopped running (I was at near 5000rpm at the time)... it restarted right away and shut down again when rpm got up to around 5K. Restarted again, right away and shut down immediately after planing out.... then on easy restart it rattled and shook and I knew I had bought the store... center cyl had severely scratched up the cyl wall.... I could see trace amounts of metal on the spark plug! I janked the head to take a look and it was a disaster... Yamaha put a new power head on under warranty, whew!!... Also have had same problem with a 40hp 3 cyl Yam and a 90 Yam (also 3 cyl)... So this problem can be elusive and act like something simple like fuel delivery etc.... best to be cautious and not take risk! ANytime an engine just shuts off the cause should be identified asap! Hoping carbon jacking is not the problem.... Clark
SWarren posted 02-12-2001 12:38 PM ET (US)     Profile for SWarren  Send Email to SWarren     
My 90 Yam had a similar problem, where it would not run at high speeds but worked fine at idle and low speed. It was a bad coil. It is pretty rare on yamaha, and was only found after all carbs were cleaned and fuel pump and filter changed. Needless to say they still charged me for all the work on carbs that really did not need to be done.
hardensheetmetal posted 02-12-2001 09:47 PM ET (US)     Profile for hardensheetmetal  Send Email to hardensheetmetal     
SWarren- You may not know it but you may have just diagnosed my biggest problem. At the end of last season I was having problems with my 1988 225 Yamaha, it would start and run just fine, and usually it would get up on plane and run for about three or four minutes, then the RPM would drop back from about 3800 down to around 2100 or less. I changed the fuel filter, which did nothing. Eventually, after screwing around with the motor for several days it started loosing RPMs under any heavy load (getting up on plane). Since it was the very end of the season I just pulled the boat out and figured I would deal with it this spring, and I've been worrying about it ever since. Does this sound at all similar to your problem?
SWarren posted 02-13-2001 08:51 AM ET (US)     Profile for SWarren  Send Email to SWarren     
Yes. It would start and idle fine and run fine in the lower ports on the carbs through about 2500 to 3000 and the want to cut out and off when I tried to give it more throttle. I am by no means a mechanic, so it might not hurt to ask your dealer if it is possible on your motor, but it sounds like my problem. My motor is an 87 and I run the ring free stuff in it all the time and prem gas, so carbon was not the problem.
lhg posted 02-13-2001 03:24 PM ET (US)     Profile for lhg    
Sheetmetal - I don't know Yamahas, but on a V-6 Merc that sounds like a stator problem.
Rick posted 02-15-2001 02:22 PM ET (US)     Profile for Rick  Send Email to Rick     
Thanks for the info. It looks like the fuel pump diaphram is stretched and hopefully this is my only problem. It shouldn't have a carbon problem, the previous owner swore by ring free and ran premium gas. I just installed a new pump and will try it this weekend. Tannks again, Rick

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