Question about Yamaha Boating

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My Yamaha 70 hp 2 stroke boat motor is bogging at 4500 rpm. Stored over the winter, slow starting so I added B-12 chemtool to the tank to dry any water. Finally started rough then smoothed out after running a while. Then I ran it out of fuel on the way to the Fuel Island. After filling with fuel I noticed the rpms were limited to 4500 and it would go the same speed at 2/3 throttle or WOT.

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  • Yamaha Master
  • 1,190 Answers

Clean your carbs etc !! fit a water fuel seperator inline from tank to stop problems !

Posted on Jun 10, 2014


6 Suggested Answers

  • 2 Answers

SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

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Posted on Jan 02, 2017

  • 1711 Answers

SOURCE: i have a yamaha 2

On the tachometer back you have secured a wire thread just like the one from the brakes of a bicycle. The other end of the wire is secure to the engine. This wire complete, need to be replaced.

As a test first disconnect it from the tachometer and see if ok if not then the problem is with tachometer.

Posted on Oct 03, 2010

  • 8 Answers

SOURCE: My 2 stroke 3 cylinder carbureted 90 hp Yamaha

Just pull them apart and clean.

Posted on Nov 07, 2010

  • 298 Answers

SOURCE: 2002 YAMAHA 150 hp OUTBOARD MOTOR at 1/2 throttle

Some out board fuel tanks have a breather that you have to unscrew (sometimes located on the filler cap - otherwise near it). If applicable check that it is open. Otherwise try unscrewing the cap on the fuel tank slightly so that air can get in - does this solve the problem? If yes then it is a blocked breather hole - ***** it out with a pin or needle.
Not all fuel tanks have a filter in them but if yours does then remove it and rinse the filter mesh out in a bowl of petrol or white spirit.

Posted on Feb 18, 2011

  • 184 Answers

SOURCE: tohatsu outboard 15hp 2 stroke was running great,

First: with flashlight or mirror look down the carb- with switch off- and gear and throttle wide open and see what the butterfly valve inside there is doing. It should be parallel to the air flow.

If not you need to find the actuator am and be sure it moves with the control and opens all the way.

Next make sure the timing plate under the flywheel moves at the same time the throttle is opened. Then -using timing light- see if the timing is set to the correct "wide Open throttle" - this is a 2 man job done at sunset with good marks on the flywheel (don't wear a tie). This can also be done static by running it out of gas and using the pull cord- if it has no safety interlock.

Last- and the saddest part- is the compression test. The strength of the reading is not as important as the similarity. When I worked on Chryslers, they were bad if the two readings were as little as 8# apart. The minimum reading should be over 80#.

Posted on May 26, 2011

  • 1978 Answers

SOURCE: I have a 2001 Yamaha

Several things can cause the problems you describe. 1) If there is a mouse nest in your waterbox, adding water to the nest plugs the exhaust causing the poor running. When it drys out on land it runs fine. Cleaning out the water box will not be easy on that model but a careful inspection of the exhaust outlet may tell if critters are the cause of your problems. 2) Corrosion in the teeter/totter needle inside the carburetor can also cause low power on the water. Try cleaning the carburetor. Warning: be very careful not to modify or stretch the spring on the teeter/totter. 3) Water in the electronics box can cause shorting and low power. Open the electronics box and inspect it for moisture. Leave it open over night to dry it out and put grease on the o-ring seal when reinstalling the cover. 4) One last possibility would be burnt or stripped screw on tops on the the spark plugs (if they are not solid top plugs), fouled spark plugs, or burnt out resisters in the in the spark plug caps. Replace the plugs ($3 each) and the spark plug resister caps($5-$8 each), make sure the screw on domes of the plugs are on tight. with any luck one of these checks should fix the problem you describe.

Posted on Aug 29, 2011

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Its time for a complete carb cleaning and setting by a qualified professional... When you say ran fine out of water.. you DID have the "ear muffs" connected to provide water to cool the engine..?? If you DID NOT.. you MAY have more serious issues. Take this to a qualified pro!!

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