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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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It starts and idles will not accelerate smoothly, has been

Customer Question

it starts and idles will not accelerate smoothly
JA: Sometimes things that you think will be really complicated end up being easy to fix. The Marine Mechanic I'm going to connect you with knows all the tricks and shortcuts. Tell me a bit more about what's going on so the Marine Mechanic can help you best.
Customer: has been sitting for about 6 months ... was difficult to start but now starts and idles.... won't go much above idle with out missing and stalling... suspect main jets are clogged
JA: Is there anything else important you think the Marine Mechanic should know?
Customer: that should do it
Submitted: 4 months ago.
Category: Boat
Expert:  Jason replied 4 months ago.

Hello my name is ***** ***** am I speaking with? I read what you wrote but do not see any kind of model information. What are you working on exactly?

Customer: replied 4 months ago.
it is a 2004 150 hp Honda 4 stroke
Expert:  Jason replied 4 months ago.

A 2004 Honda 150 is a fuel injected engine, not a carbureted engine. You wrote that you suspect the main jets are clogged. This obviously can not be a carburetor jet issue if the engine is EFI. Are you positive on your model year?

Customer: replied 4 months ago.
you are correct... I do believe it is an efi system.... looks like a throttle body
it is a 2004 on a 2003 boat.... sure of that
Customer: replied 4 months ago.
I usually keep a fuel treatment in it... was lax this past storage period... has a 60 gallon tank.... full
Customer: replied 4 months ago.
waited till the last minute to check everything... planning on a fishing trip in the morning.... everything is working except won't throttle up
Expert:  Jason replied 4 months ago.

Got it. Being and EFI engine 90% of the time it needs to be hooked up to a scan tool in order to see if there are any sensor issues. That being said. What is the history on this engine? When was the last time it ran correctly? How often does it get run? Any idea on the engine hours? How old is the fuel itself, is it all new starting from a pumped dry tank, a mix of new and old, or something else? Have you done any troubleshooting on your own yet?

Customer: replied 4 months ago.
I always fill the tank after each outing... usually about 20 gallons used for a full days fishing.... it was last run in October
no issues then... about 400 hours total time on engine...... oil and filters changed just before last trip
Customer: replied 4 months ago.
I am a certified Honda motorcycle mechanic... but most of my experience is on carbureted models
Customer: replied 4 months ago.
i use it maybe 10 times a summer
Expert:  Jason replied 4 months ago.

If it was last run in October there is a 50/50 chance the gas has spoiled to the point that the outboard will not tolerate it. (outboard engines are extremely picky on fuel quality). Steps 1 and 2 are to first get a portable fuel tank, fill that up with brand new gas, and hook that up to the engine and then 2nd, change all of the fuel filters. I know that sounds basic but that is exactly where we start in the shop. Is that something you can do or?

Customer: replied 4 months ago.
i walked out and tried it again and it throttled up just fine... then put cover back on it and it is doing the same thing.....
Customer: replied 4 months ago.
seems if the fuel was so bad it would not have throttled up
Customer: replied 4 months ago.
thinking one of the valves must be sticking
Expert:  Jason replied 4 months ago.

Are you reving the engine up in neutral or is the boat in the water and in gear trying to run it under a load?

Customer: replied 4 months ago.
on the bright side ... there are several marinas where i am going tomorrow....just hate to spent half a day in there waiting.... throtting up in gear with water running through flush ports with muff
Customer: replied 4 months ago.
no load on engine
Expert:  Shane Creekmore replied 4 months ago.
Just read question and wanted to warn you about throttling up with it out of the water. Unless it is hooked to a dyno everytime you rev it, its like kicking a grenade. Without the back pressure the weight and speed of the prop can cause the gearcase to shatter or the prop shaft to break