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Ask Dominick Your Own Question
Dominick, Marine Mechanic
Category: Boat
Satisfied Customers: 1009
Experience:  25 Years Experience as Mechanic, 20 Yrs Boat Yard Owner/Mechanic, Factory Certified
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I have a 2009 yamaha 212ss 1.8 liter gh output motor that is

Customer Question

i have a 2009 yamaha 212ss 1.8 liter high output motor that is not idling properly.
ichanged out the tps and is still doing the same thing. thinking it could be the wire harness?
what would be your take on this issue
Submitted: 4 months ago.
Category: Boat
Expert:  RSRBOB replied 4 months ago.

Hi and thank you for your question.

I would like some more detail on this issue please. In addition to some specific questions I have, any additional information you have along the same lines of my questions could be beneficial as well.

Specifically, I would like to know.

1.) How many hours are on the boat?

2.) How long has it had this symptom?

3.) When was the last time the engine was serviced? (both hrs of engine use and calendar time)

4.) What was done on the last service? (parts and labor)

5.) Other than not idling properly, is the engine performing normally?


Customer: replied 4 months ago.
Engine Hrs. 170
Engine was just rebuilt
Runs great otherwise... Just shuts down at idle.
Fuel line is good..
Starter was replaced
And manifold replaced
Changed out throttle position sensor
The compression is good.
Customer: replied 4 months ago.
I got the boat last month and rebuilt the engine.
Expert:  RSRBOB replied 4 months ago.

Thank you for the additional information.

What parts were replaced in the rebuild, and what had happened that necessitated the rebuild?

It has never run correctly since the rebuild?

What were the results of the compression test for each cylinder? Apologies but good is too subjective.

Customer: replied 4 months ago.
Manifold, starter, oil, plugs,Saltwater, frozen starter, corrosion on manifoldNo has never idled correctly since the rebuildNot sure of the results but I had tested and was told they were good.
Expert:  RSRBOB replied 4 months ago.

Thank you for the additional information.

I am not terribly comfortable with a vague statement that they gave you of the compression being good. However, we will press on and look at some other things before considering that again now.

One additional question I have for you is were the camshafts/cylinder head removed?

My next suggestion would be to look for an air/vacuum leak on the intake. The easiest way to find this is start the engine (on the flush kit for cooling) and spray contact cleaner around all the joints between the throttle body and the cylinder head. If you hear any change in the idle, either revving up or wanting to stall, you have an intake leak. It is ok to remove the air filter/flame arrestor to perform this test. At idle, it will not affect the running of the engine. Do not expect it to rev up with the air box off however.

Something else that could tip you off about that is spark plug colors. Have you pulled them out and looked at them to see if they are all consistent in color? Which also brings to mind, have the spark plugs been changed lately? If you have any question as to whether the spark plugs are good or not, please take a picture of them in the order 1,2,3,4 Bow=1, stern=4 and attach to this thread.

If you have one that is a different color from the others, it can be indicative of a problem.


Expert:  RSRBOB replied 4 months ago.


Just following up with you on the status of your boat. Have you made any head way on resolving the issue or are you still in need of assistance? Let me know if there is something I can help you with.



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