985crabs
Captain
2000 V1900 Bay Series, Yamaha 150 Carb. 2
Posts: 1,309
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Post by 985crabs on Feb 13, 2017 13:53:04 GMT -6
A couple months ago I was out and my motor was running a little rough. I thought maybe I had bad gas or needed to change the separator filter. I drained the fuel tank, installed a new filter and refilled with fresh non-ethanol gas and gave it a healthy dose of Sea Foam.
Yesterday I took her out for a sea trial. Below about 3,600 RPMs I could set the throttle and the tachometer would not waiver. Above 3,600 it would intermittently drop between 100-300 RPMs for a second and then go back to normal. The motor felt and sounded like it was skipping a heartbeat. I don't like this and I don't want to run it if there is a problem.
Anybody ever experience this? Is this a symptom of something familiar? I'm imagining any number of very expensive scenarios.
Motor is a carbureted (sp?) 2-stroke.
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Post by gnrphil on Feb 13, 2017 15:42:26 GMT -6
When was the last the:
Plugs were changed
Carbs serviced
Fuel filter changed ( not the water separator)
What year motor is it?
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985crabs
Captain
2000 V1900 Bay Series, Yamaha 150 Carb. 2
Posts: 1,309
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Post by 985crabs on Feb 13, 2017 16:05:16 GMT -6
2003. I changed the plugs last summer or about 30-40 hours. I pulled the fuel filter under the bonnet and it was clean as a whistle (10 micron filter in water separator). I bought the motor 4-5 years ago from the dealer. They went all through the carbs then and had it running like a top before they delivered it to me. My only issue ever has been that it doesn't like to start when it's cold and it may idle just a little low. I have not had the carbs serviced. I've only put 143 hours on it, it's never ingested ethanol while I've owned it and I treat it with Sea Foam every other time I fill it.
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Post by gtightline on Feb 13, 2017 17:23:12 GMT -6
It is very possible that you could have some very small debri that will sometimes get past your filter, it doesn't take much to temporally obstruct a jet where you could get what you describe.Did you check the bowl for any crud that might be floating around in there? You could also check to make sure that the needle valve in the float is not sticking due to any type of gumming...BTW my 115 Yamaha is also cold blooded and takes me putting the motor in neutral and priming those carbs good before it fires. It has been like that since it was new... Just saying.
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Post by freezerfiller on Feb 13, 2017 18:59:41 GMT -6
Since it runs good at low rpm and has the issue at high rpm, I'm going to go with
1. a fuel starvation issue. Either lack of fuel flow due to clogged filter, pinhole air leak in the fuel line or bulb, or low fuel pressure from a weak fuel pump. You can get a fuel pressure gauge and check your fuel pump/fuel flow situation pretty easily and track it down from there.
2.The other likely culprit would be a malfunctioning high speed jet. I'm no Yamaha mechanic, but many outboard carbs have 2 jets, a low speed jet and a high speed jet. Usually the low speed jet is what you adjust to get a good idle. The high speed jet is usually just a hole that's not adjustable. It could be malfunctioning either because it's clogged, or you could have a leaking gasket inside the carb allowing it to draw air rather than fuel. This can be a big problem because if you have a cylinder that's not getting fuel, it's not getting oil either since it's mixed in the fuel. As far as checking the jet possibility, Usually you can take off your intake shroud where you can see the carbs, hook up some water, or put the boat in and rev the engine to the point you hear the miss. Shine a good flashlight into the carbs one at a time. You should see fuel dripping into the throats of the carbs that are functioning properly. If you see one that is not getting fuel, that's your problem child.. Obviously don't spend a whole lot of time doing this if it's not getting fuel oil mix.
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Post by Juan on Feb 14, 2017 7:47:00 GMT -6
Shine a good flashlight into the carbs one at a time. You should see fuel dripping into the throats of the carbs that are functioning properly. I'm glad you told him to use a flashlight and not a lighter! He's a Cajun. rofl Good luck crabs.. You might try running on a portable fuel tank, if it runs the way it should, you could eliminate the carbs and filters and start looking at the fuel lines and primer bulb. |
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985crabs
Captain
2000 V1900 Bay Series, Yamaha 150 Carb. 2
Posts: 1,309
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Post by 985crabs on Feb 14, 2017 9:58:47 GMT -6
Thank you gentlemen (and Juan) for your input. I should revise my issue description just a bit. I have noticed hiccups while running at idle speed on the muffs as I make sure it's going to start the night before a fishing trip. So,if it's shaky at idle and in the upper ranges, but solid in mid-range, does that change the diagnosis any? I hadn't thought about a pinhole leak in a fuel line or bulb or even a weak fuel pump, but it makes sense. I guess I need to start eliminating things from the list one by one or simply take it to someone who knows what they're doing and hope I see the boat again before the spring fishing season is over.
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Post by gnrphil on Feb 14, 2017 11:52:10 GMT -6
Just a thought, check the fuel lift pumps. Easy to do, just loosen the mounting bolts a little so they are free from the block then squeeze the bulb and check for leaks, if the diaphragm is damaged it would leak into the crankcase and you'd not notice.
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yolo
Ensign
Posts: 626
Location: Back to Manasquan Inlet, NJ
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Post by yolo on Feb 14, 2017 13:35:12 GMT -6
Take the filters off and reinstall them (dont have to change) just to make sure no air is getting past any of the seals.
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Post by freezerfiller on Mar 9, 2017 16:50:47 GMT -6
Any updates on this Crabs?
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985crabs
Captain
2000 V1900 Bay Series, Yamaha 150 Carb. 2
Posts: 1,309
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Post by 985crabs on Mar 10, 2017 9:30:34 GMT -6
I did what I felt comfortable doing (new plugs, reinstall filters, fresh fuel, etc.) and decided it was likely a carburetor issue. As it hasn't seen a mechanic in 5 years, I decided to take it to the dealer to let a professional go through it. It's still there. They cleaned the carbs and report that it idles well and runs better, but they are concerned that there is a fuel restriction issue. The latest plan is to run it on the water with an external fuel supply. It's been windy, 20-25 mph, or rainy here for the last week and a half so I don't guess they've been able to do that yet.
It does seem that if one does not make one' living on the water, the boat mechanics don't give one the highest priority.
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Post by Juan on Mar 11, 2017 7:09:25 GMT -6
Don't worry, I'm betting you'll be their #1 priority when it comes time to bill ya!  |
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985crabs
Captain
2000 V1900 Bay Series, Yamaha 150 Carb. 2
Posts: 1,309
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Post by 985crabs on Mar 13, 2017 12:00:56 GMT -6
Don't worry, I'm betting you'll be their #1 priority when it comes time to bill ya! Oh, I'm sure that's true. Thanks for the encouragement. |
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Post by gtightline on Mar 14, 2017 12:22:00 GMT -6
Air leaks around the carburetor manifolds can also cause a surge as you describe. Carburetor manifold leak, it doesn't take much....Just a thought is all.
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Post by freezerfiller on Mar 14, 2017 17:07:54 GMT -6
Since it is March Madness with bracketology everywhere, I am putting my money on a low pressure fuel pump like funny flag phil mentioned. Not certain what a fuel lift is but I think we are talking about same thing. Yeah, carbed engines only have one fuel pump, it "lifts" the fuel to the carbs. Fancy HPDI guys like Phil have two fuel pumps, the lift pump which gets it to the engine, and the pressure pump which gets it under enough pressure to spray fine enough to ignite directly into the cylinder.. hence High Pressure Direct Injection.... |
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Post by gnrphil on Mar 14, 2017 19:31:33 GMT -6
Since it is March Madness with bracketology everywhere, I am putting my money on a low pressure fuel pump like funny flag phil mentioned. Not certain what a fuel lift is but I think we are talking about same thing. Yeah, carbed engines only have one fuel pump, it "lifts" the fuel to the carbs. Fancy HPDI guys like Phil have two fuel pumps, the lift pump which gets it to the engine, and the pressure pump which gets it under enough pressure to spray fine enough to ignite directly into the cylinder.. hence High Pressure Direct Injection.... Actually I have 4 fuel pumps  , 2 low pressure (lift pumps) 1 medium pressure and 1 high pressure. beerchug |
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985crabs
Captain
2000 V1900 Bay Series, Yamaha 150 Carb. 2
Posts: 1,309
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Post by 985crabs on Mar 15, 2017 7:00:27 GMT -6
Anyone else want to place their wager? The mechanics have informed me that my rig is ready for the water again. I will offer full details when I understand them.
For the consolation round, perhaps you all should offer a guess as to what I'll be charged for their services?
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Post by gnrphil on Mar 15, 2017 8:15:41 GMT -6
$145.00 plus the taxes.
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Post by Juan on Mar 15, 2017 18:01:09 GMT -6
I'm guessing 3 hours labor @ $80 an hour = $240. Plus parts $130. for a total of $370 plus tax, title and destination charges |
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Post by freezerfiller on Mar 15, 2017 19:45:20 GMT -6
I'll say carb rebuilds $345 out the door
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