Yamaha Dual Controls Problem

[igofishn]

I have twin 1991 150 yamaha's. I normally cruise at 3,600 rpm and both controls are at the same foward postion. My last few trips I noticed that I have to move the starboard control about 3/4 inch further forward in order to get to 3,600 rpm. Since this started, once in a while this motor rpm surges up from 3,600 to 4,000 then back down to 3,600. Both controls move in and out of gears with no problems. Is this a start to a problem with this motor or are the control cables starting to fail or need adjustments? Any help would be appreciated.

Thanks

 

[rodbolt]

Re: Yamaha Dual Controls Problem

as the cables are a single strand of solid stainless, I would say your engine is developing an issue. when was the last time you brought them up to WOT together ?

 

[igofishn]

Re: Yamaha Dual Controls Problem

Enginees are getting old or are old and I don't like to push them very hard. I can't say the last time I ran WOT. Maybe the beginning of the season up here and I don't recall having any issues. I am going to run the boat later today. Is there anything that I should look for while at WOT. I should get 5,000-5,500 rpm? This engine does sneeze once in a while when first started but once warmed up runs ok.

Thanks

 

[Shoesole480]

Re: Yamaha Dual Controls Problem

I have twin 1991 150 yamaha's. I normally cruise at 3,600 rpm and both controls are at the same foward postion. My last few trips I noticed that I have to move the starboard control about 3/4 inch further forward in order to get to 3,600 rpm. Since this started, once in a while this motor rpm surges up from 3,600 to 4,000 then back down to 3,600. Both controls move in and out of gears with no problems. Is this a start to a problem with this motor or are the control cables starting to fail or need adjustments? Any help would be appreciated.

Thanks

Remove the engine covers and place both throttles at W.O.T. and ck. to see if you are getting the same throttle lever position on both motors (should be just before break-over point @ throttle-shaft) Also, check to see if timing base linkage is in good shape with no slack or loosness and ck. to see if timing base moves smoothly as you throttle up and down. If all checks out ok, the you should ck carbs/fuel delivery. Also, never neglect the spark plugs, they are too often over-looked. I can't begin to count all the times I had a hair-pulling problem that finally came down to spark plugs. Spark plugs can test fine in the shop, but under operating conditions, I have seen too many of them fail at higher RPMs.......good luck

 

[igofishn]

Re: Yamaha Dual Controls Problem

I didn't get a chance to get down to the boat today. But I will try what you said. Also, This season I replace the 2 fuel pumps, spark plugs and fuel filter. Everything was fine up to a week ago. I will pull the plugs and inspect them. Also I will check the fuel pumps maybe the sneezing messed up one of the fuel pump diaphrams. I have never cleaned the carb's in the 10 years I owed this boat, it might be time? I have heard that it should be done every 3-4 years! I have had only very minor problems with these engines in the past. They have been very relaible. Thanks for you response. I will let you know what I find.

 

[igofishn]

Re: Yamaha Dual Controls Problem

Rodbolt,

I ran the boat today WOT, 5,000 rpm on port, 4,800 rpm on the starboard motor. Also, ran boat at 4,500, 4,000 and 3,600 and the boat didn't sugre today but the starboard throttle is still about 3/4 inch ahead of the port. I noticed today that when I lowered the engines into the water there was some fuel in the water? The boat started fine but it started sneezing at idle. I reset the pilot screws to 1.250 turns out from the seated position but still sneezing. Is there any tolerance of a .25 turn futher in or out on that setting? Maybe time to clean carbs?

Thanks for your time.

 

[rodbolt]

Re: Yamaha Dual Controls Problem

it may well be.
if both engines magneto arms contact the arm stopper then I would look for engine issues.
cable stretch is just not likly on that setup.

 

[igofishn]

Re: Yamaha Dual Controls Problem

Both magneto arms are hitting the stop at WOT like you said. The 200 rpm differecence is that something to be majorly concerned about. I have about 4 weeks left to my season another maybe 10-15 hours or so of runnng, would you run this way and pull down the carbs during the off season? Also that fuel in the water I see is that normal, never noticed it before?

Also, my port control is alot tighter then the starboard is there a tension adjustment on them?

Thanks again

 

[igofishn]

Re: Yamaha Dual Controls Problem

Sorry for the long delay but I pulled the carbs off last week. Found a broken pilot screw in the lower carb. Pin was stuck in the opening so I purchased a new carb and rebuild kits. Soaked and cleaned and rebuilt the carbs. Checked compress 113-115psi on all 6, changed plugs, fuel filter, fuel pumps and water seperator. Installed carbs this morning and engine purred like a kitten. That engine always had a slighly rough idle since I purchased the boat, not any more. 5,000 rpm on both motors now and throttles are at the same position.
As you stated in other posts, rebuilding the carbs was not at all difficult.

As always, thanks again for steering me in the right direction guys.

Now back to Striper season.