2009 Yamaha 60 HP (F60TLRH) sometimes Surges or Revs Up at Very Slow Docking Speed

[bbakernbay]

We just purchased a Sunchaser 820 Pontoon Boat with a Yamaha 60 HP 4 stroke. 6 years old but very little use, under 10 hours. Engine starts and runs beautifully except that on 3 occasions in the last week when I was doing very low speed docking and I slightly adjusted the throttle the engine would surge as RPMs increased and Of course made a noise as I tried to get in back in Neutral. This doesn't happen every time I dock.

Yesterday the RPMs were going crazy and I had to shut engine off. I waited 20-30 seconds and it started and no further problem.

I have read all 12 pages of High Sierras post on the somewhat similar issue he had with his F150 and Rodbolts and others helpful suggestions. I have read of other posts where anti-siphon valve in fuel tank was the culprit with crud gumming it up. Others suggest Throttle Speed Sensor could be faulty.

My day or so Google research indicates it may be the Idle Air Control Valve needing cleaning or replacement.

We dock at a small campground and Marina and the owner looks after many types of engines but I doubt he has laptop software to analyse fault codes so I am trying to narrow down possibilities before I leave it with him. I may have to trailer it into North Bay, ON to see the Yamaha Tech but hopefully we can deal with it at the marina.

Dose of Ring Tune or SeaFoam probably wouldn't hurt.

Engine runs beautifully except for these occasional surges at very low speed when docking. It concerns me especially in a high wind situation and of course my wife is scared to operate it after 35 years running our 90 hp Mariner without any issues.

Hopefully the excellent Forum Members on iBoat can offer some suggestions.

 

[bbakernbay]

The last 3 or 4 times docking I have not had any issues whatsoever.

I am thinking that with my inexperience with new boat, motor and throttle I may have been a little hyperactive with the throttle jerking it around too much freaking out the throttle position sensor or something similar.

I bought a bottle of Yamalube Ring Free today and will add a few ounces to the tank as I really don't know how long that fuel has been in the 10 gallon tank.

The fuel gauge hardly moves, going to be a big fuel saving vs. old 90 hp Mariner, of course no more tubing for grandkids now with pontoon boat instead of bow-rider runabout.

Any advice is welcome.

 

[mjf55]

Not too much except get rid of the old gas. Use it in a lawn mower, bring it to a dump, where ever you can. Clean tank and use fresh gas. Put 1 gallon of gas in , ring free in to decard the engine ( i think 10 oz per gallon). Then when done, fill tank, ring free for normal use ( 1 oz per gallon ). ( check actuall directions). Run the boat and get comfortable. Then see if there is an issue.
Just my thoughts.

 

[99yam40]

verify the amount of RF for decarb , not sure 10 oz per gallon is correct

 

[bbakernbay]

It must be an issue more than the gas although I did add the Yamalube Ring Free this morning.

Started up on second key turn and ran fine around 3,500 rpm as it was poor visibility, throttled down perfectly at Marina as it should for docking.

It then took 3 starts to fire up after a 15 minute run and sat for 15 minutes.

After it started it was revving higher than normal when I left Marina.

I was running at full throttle back from Marina and then slowed down to dock at our cottage but revs remained high and it wouldn't throttle down to real slow speed which could be a problem in strong winds or at Marina.

It looks like a trip to the Engine Tech.

I see that eBay has the Disgnostic Cable and software for hooking up to laptop, may be a useful tool to have.

 

[bbakernbay]

Now it is very difficult, almost impossible to start and once it did it lurched for first 500 yards before returning to normal.

Calling Mechanic tomorrow.

 

[bbakernbay]

Today I drained the 20 gallon fuel tank and found lots of debris, water and cruddy liquid in the last gallon.

Cleaned the tank thoroughly, added Stabil and Yamalube Ring Free and filled the tank with fresh gas.

I checked 2 of the 4 plugs and found them good, light tan colour but no deposits or carbon.

The mesh screen on the tank's intake tube was perfectly clean.

I then removed fuel filter reservoir and surprisingly it looked clean.

I removed the fuel filter and it looked clean and washed it in solvent and no debris appeared.

Then I loosened the brass screw and rearranged the small fuel drain line and then retightened the brass screw.

Put in a new battery while other was recharging.

The engine started on first turn of the key and we went to the Marina for topping up gas tank.

Let it idle for 15 minutes, no issues, engine purring beautifully.

Motor ran flawlessly at full throttle and low docking speed.

I thought "Problem Solved".

Left Marina to take kids fishing and we anchored and after 30 minutes we decided to move on and engine needed 3 or 4 key turns to start.

Fished at second spot for awhile then decided to head home.

Engine would not start after repeated attempts and finally caught about 12th try and only barely and just barely.

Engine ran well going home at full throttle and very slow docking speed.

I am really baffled about what the issue might be.