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  Engine Bogs Down, Yamaha 130 HP

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Author Topic:   Engine Bogs Down, Yamaha 130 HP
prj posted 10-11-2010 02:26 PM ET (US)   Profile for prj   Send Email to prj  
My 1989 Yamaha 130 HP 2 stroke is having a predictable and consistent running problem. The motor bogs down at 2000 RPM and struggles through a narrow band up to about 2700 RPM, where it catches and slowly spins back up to run smoothly.

As I push the throttle up past the 2000 RPM mark, it stutters and staggers until I nurse it up around that 2700 RPM mark. At all engine speeds above this, it runs smooth and is developing full power and speed.

It feels like a fuel delivery problem, as if the fuel is coming intermittently starting at 2000 RPM. This doesn't make sense to me though as it runs well at high RPM / fuel consumption speeds.

It also feels a bit like an electrical problem, as if its not getting sufficient spark to ignite the fuel that is getting pumped into the cylinders.

Other relevant info:
I pulled and cleaned all 4 spark plugs. They were a bit carboned up from slow trolling for Lake Michigan salmon, but looked good, gapped appropriately and wire brushed clean.

I replaced the fuel filter with a new one.

I poured a couple ounces of Water Zorb in the fuel to see if that might assist with some water in the fuel tank problem.

The engine is running a bit rough in the low RPM range, below 2000 RPM. Again, this feels electrical in nature.

Any advice appreciated.

Tohsgib posted 10-11-2010 02:30 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
Yamaha uses idle circuits in their carbs...they need to be cleaned. Run her lean and you will buying a new engine soon.
contender posted 10-11-2010 02:32 PM ET (US)     Profile for contender  Send Email to contender     
I agree it does sound like a fuel problem...You have two jets in the carbs, low speed ones maybe clogged. They are easy to rebuild if you can turn a screwdriver. Get the factory kits from Yamaha or Boats.net...good luck
prj posted 10-12-2010 10:43 AM ET (US)     Profile for prj  Send Email to prj     
Thanks Nick and contender.

Can I simply clean the carburetors or will I need to "rebuild" them with a purchased kit? I haven't done this before, but I'm reasonably capable and completely unafraid.

meridian posted 10-12-2010 10:58 AM ET (US)     Profile for meridian  Send Email to meridian     
I would try some seafoam or other products like this before the rebuild. It's quick and cheap.
Tohsgib posted 10-12-2010 11:21 AM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
Just clean them out real quick...only 2 carbs right? No need for a kit inless you rip a gasket which I doubt. Some cleaner and compressed air. A set of torch files($6 NAPA) work REAl good to get in the jets and clean.
contender posted 10-12-2010 02:38 PM ET (US)     Profile for contender  Send Email to contender     
Tohsgib is correct: be careful taking them apart, clean them, and put them back together, just do not rip any gaskets, air compressor, and some cleaner is all you need, and you will be fine...
jimh posted 10-14-2010 08:03 AM ET (US)     Profile for jimh  Send Email to jimh     
Pat (AKA Homeaside) had a similar problem with his V6 Yamaha engine. It ran well except in a certain engine speed range around 2,000 to 2,500-RPM. His mechanic found a problem with the carburetors. If I recall correctly, there were orifices ("jets") that were clogged.
home Aside posted 10-14-2010 07:02 PM ET (US)     Profile for home Aside  Send Email to home Aside     
For the last 2 1/2 seasons I had a problem with my 1985 Yamaha 225 when Decellerating between 3100 RPMs - 2800 RPMs, the engine would bog and almost stall. There was no problem accelrating up through the power range.

I went through full tune-ups, changed fuel filters, and this and that with no success diagnosing the problem.

This September when getting the boat ready for winter layup I decided to fork over the $90. to have the engine put on the Dyno. It was discovered that the middle carburator had developed a lot of corrosion to the jets and adjustment screws. The mechanic felt he would have broken the carb if he had tried to work on it while it was on the engine. He subsequently removed the carburator, was a able to dismantle it, clean off the corrosion,replace jets & adjustment screws, and the engine is running fine. The boat is now in winter indoor heated storage and I won't be able to test the motor for myself until Spring.

As far as history when new the boat came from Texas and I believe it probably had limited use in salt water early on, after that it spent several years in Missouri & then came to Michigan sometime around 2003-2004.

That is my best description of the problem as it was diagnosed.

Pat

prj posted 10-18-2010 03:32 PM ET (US)     Profile for prj  Send Email to prj     
Awww man, contender, you're selling this project a little short in suggesting that its as easy as turning a screwdriver...

So I'm into one carburetor and find I cannot separate the lower bowl from the upper portion (butterfly valves, etc.). It feels spring attached internally yet. Are these the needle valves somehow holding the upper and lower halves together yet? If so, how do I disconnect them? If not, is it simply a matter of exerting more force?

My Yamaha Manual is not clear in this regard. Matter of fact, as best as I can tell, they even have the slow air jets mislabeled / unlabeled. Or not. Thats the problem I'm having: A complete lack of familiarity with carburetors and their makeup.

K Albus posted 10-18-2010 03:44 PM ET (US)     Profile for K Albus  Send Email to K Albus     
Patrick, you're a braver man than I am. I wish luck in getting those carbs cleaned up and put back together by yourself.
K Albus posted 10-18-2010 03:47 PM ET (US)     Profile for K Albus  Send Email to K Albus     
I can't even put together a sentence without leaving a word out. I can't imagine putting together a carburetor. Again, I wish you luck in getting those carbs cleaned up and put back together by yourself.
prj posted 10-18-2010 03:56 PM ET (US)     Profile for prj  Send Email to prj     
Fortunately for you, Kevin, they've designed your engine in such a daunting manner that one wouldn't even be tempted. Its not unlike newer automobiles, eh? I'd never consider dissembling the 4.7L V8 on my 2004 4Runner, but wouldn't hesitate to dig into my 1992 Pickup's 2.4L 22RE.

OK, so desperation and wits got me into the carburetor bowls, main and slow air jets are out. Main nozzle looks clean, floats nice, etc...

Next:
There looks to be some varnish in the bowls and I'd like to soak and clean it, as well as the jets, particularly the small orifice "slow air jets", as recommended in posts 2 and 3 in this article, I'll add.

Pretending I've never done this before, how would one go about the jet cleaning? Soak or file or thread a wire? Then compressed air to blow out, correct?

How about the bowl cleaning? May I use one of the many mostly full solvents on my garage shelf (Acetone, Best Kleen, paint thinner, TK-00 Solvent) or do I get to go out and buy yet another to add to the shelf?

Thanks gents, I'll make this a real adventure yet.

jimh posted 10-18-2010 04:34 PM ET (US)     Profile for jimh  Send Email to jimh     
Choose the carburetor cleaner solvent carefully. The master mechanics at LOCKEMAN'S have told me of stories of owners who soaked their carburetors in cleaning solvents that actually removed a finish on the metal. I'd start with something that sounds benign, and if that does not get the varnish off, move to stronger solvents.
vin1722or posted 10-27-2010 01:29 PM ET (US)     Profile for vin1722or  Send Email to vin1722or     
I would be careful of the gaskets and rubber orings with the carb cleaner you use,otherwise normal cleaners like gumout carb cleaner works well.I would not soak a carb for a long period of time or overnight.The coating on the metal could come off and then you need a new carb(s.
K Albus posted 11-05-2010 07:40 AM ET (US)     Profile for K Albus  Send Email to K Albus     
How's the carb project going, Patrick?
prj posted 11-08-2010 10:45 AM ET (US)     Profile for prj  Send Email to prj     
The carb cleaning project went great, Kevin. Easy as turning a multitude of unfamiliarly shaped and sprung screws ; )

Got them (two double-bowled carburetors) disassembled and thoroughly cleaned with a new spray can of carb cleaner. (As an aside, the ingredients on the can of spray carb cleaner looked to be an exact match to all of my current solvents blended together). Varnish came off readily with some soaking and a toothbrush. Visible gunk constricting the low speed air jets cleaned out and a compressed air blow through all had it looking good.

I reassembled in short order, catching the tiny O rings that could easily be forgotten and protecting the gaskets at joined parts. Reinstallation was a modest challenge, with fuel line connections and some other appended contraptions and gyzmos whose functions I have absolutely no idea about. But it came together swimmingly!

Of course, the engine wouldn't run at all upon my initial test, so I took it to an actual mechanic...

I'll wrap up this article upon its return.

prj posted 11-12-2010 01:24 PM ET (US)     Profile for prj  Send Email to prj     
To update this adventure, I got the boat back a couple days ago. Mechanic said that needle valves were still gunked up a bit. For whatever reason, I didn't clean them in my initial pass and that mattered. Cost was a reasonable and expected $250 (3 hours at $75/hour plus tax and shop material).

Additionally, the pilot screws, which control who-the-hell-knows-what, didn't work per Yamaha manual specs of 7/8 +/- 1/4. They required more turns out, perhaps 1.5. This I knew from their original positioning before I muddled it up.

I got out on Lake Michigan yesterday to test the engine and enjoy the last of a string of 4-5 days of rare 60 degree November weather. Motor started great and ran well, but still didn't idle in neutral, occasionally coughing and dropping RPMs between 700 and 500. It would die if allowed to. Idle in gear was also low, running down to 5-600 RPMs when specs and previous experience had a smooth and steady in gear idle at about 700.

The surge and dead spot was gone, so cleaning the carburetor was non-specifically beneficial, i.e. cleaning all the parts fixed the part that was causing the problem.

I took a high speed run and hit 5600 RPM and 44.2 MPH in a light 4-5" chop, enough to loosen up the hull from the water.

I'll make a call to the mechanic and see if I can fix that idle speed to achieve my original performance. Hate to drive the boat back down there again.

The reason I'm pushing this repair late in the fall is I intend to trailer the boat to the Chesapeake Bay in December. I don't want a faulty engine out at the CBBT on an outgoing tide in winter.

Tohsgib posted 11-12-2010 02:28 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
Honestly most engines need to be "fine tuned" in the water. A simple adjustment while in gear tide to a dock when warmed up should fix it. It is not uncommon to have to do so after a carb rebuild. Price was fair as well.
Tohsgib posted 11-12-2010 02:29 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
That should ne TIED to a dock
prj posted 06-04-2011 05:23 PM ET (US)     Profile for prj  Send Email to prj     
My most excellent carburetor saga comes to an end here less than 6 months since I started.

Thanks to forum members Buckda and Gep, I sourced a replacement lower carburetor from a Yamaha 130 to replace my damaged lower, with worn air adjustment screw nibs snapped off in their tiny orifices and unable to be removed causing the chronic and difficult to diagnose sneezing.

Easy as turning a screwdriver! Well, as long as you have a thick wallet, a full offseason, a good tow vehicle, a known donor engine, strong confidence, no remorse and reasonable patience...

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