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Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 15675
Experience:  Degree in Marine Technology. Gas and diesel marine mechanic.
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I have just bought a boat with a 2004 engine 50hp 4 stroke

Customer Question

hi, i have just bought a boat with a 2004 engine 50hp 4 stroke that has only done 19 hours (nineteen).
it will rev normally with the cover off and pressing the butterfly linkage. however under load or just reving with the lever, it sputters and dies at higher revs
Submitted: 1 year ago.
Category: Boat
Expert:  Jason replied 1 year ago.

Hello my name is ***** ***** am I speaking with?

If you hammer the throttle does the engine start to build RPMS and then fall on it's face, or does it pretty much fall on it's face right away?

How old is the fuel you are trying to burn? Have you done any testing on your own?

Customer: replied 1 year ago.
peter ,
Forest of Dean UK
changed the fuel , , new fuel,
starts to build , boat speed about 1/2 way to planning then dies,
previous owner never tried to plane hull,
(possibly never set up correctly 11 yrs ago,)
regards peter
Expert:  Jason replied 1 year ago.

That can be fuel starvation. Is the fuel tank a portable one, or built into the boat? Have you tried squeezing the primer bulb over and over to see if it would make a difference?

Customer: replied 1 year ago.
Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Expert:  Jason replied 1 year ago.

Phone service is available for US residents. You wrote something about UK. Do you live in the US or in the UK?

Customer: replied 1 year ago.
i don't think so because as soon as i reduce the lever the engine recovers, instantly,
Expert:  Jason replied 1 year ago.

What i'm thinking is either the engine is starving for fuel, or there is something going on inside of the carbs, and that can include being dirty, or having a sticking float.

What I would do is run the boat again, and have a helper drive while you pump the primer bulb over and over as fast as you can.

1. If the primer bulb sucks flat, or will not easily reinflate. The fuel tank is either building up a vacuum, or there is a blockage of some sort in the tank, fuel line, or the bulb itself is bad.

2. If pumping the bulb allows the engine to run better, the fuel pump is weak and not keeping up.

3. If no difference, the problem is going to be in the carbs, and they would need to come off and be rebuilt.

Does that all make sense? If yes, did you have any further questions on the issue?

Expert:  Jason replied 1 year ago.

I think that should do it. But I work for tips so I do want to make sure you are happy with my service before you go. If you had a further question on the issue by all means feel free to ask. If not, Just in case you do not understand the way the website works (and some folks do not). You do have to put forth a positive rating in order for it to credit me for helping you. When ratings are not done, the website simply keeps your deposit and they will not credit me. The ratings box is located at the top of the screen. To rate, you must select the star you wish and also confirm it. Please let me know if you run into any problems or errors when trying to do it. If you do have a problem, or if you can not see the ratings box which is at the top of the screen. Please reply back "I rate Jason's service _______" and fill in the blank.

Questions do not close out, so if you have to come back later on with follow up questions to the issue you still can even after doing a rating.

Thank you

Customer: replied 1 year ago.
if it was fuel stavation , the engine would not give high reves when reved by hand.
i live in the uk.
the engine has only done 20 yrs from new.
what else is altered when pushing lever forward?
the carb butterflys and ???what, ?
adjusting timeing , is there a spark advance/ retard?do you have any diagrames of the carb? fuel set up?
Expert:  Jason replied 1 year ago.


Expert:  Jason replied 1 year ago.

What changes between reving it by hand and throttling it up in the water is when you are in neutral there is no load on the engine. When there is no load, the engine is simply spinning the weight of the crankshaft and pistons. It's not actually trying to make any power. When the boat is in the water it is trying to make 50 horsepower. does that make sense, load vs no load?

On the carbs, this typically isn't something you can fix yourself as special tools are needed, but I do have all of the manuals and diagrams. What did you need? Can you open up PDF files?

Customer: replied 1 year ago.
Morning Jason,
yes i can open PDF files.
Yes i am aware of the load / no load,
but that would not explain why the engine fails when reving it purely on the lever , but will rev by hand .
yet it will not rev by hand when under load (with the cover off in gear )
this is why i'm trying to establish if/where there is an advance /retard mechanisum somehow connected to the lever, that has not been correctly adjusted,Yesterday i noticed that the steering of the engine had a massive bias to one side , . . . so no time has been spent prior to delivery on setting things up correctly. . what ? could / should be adjusted when initially connecting the remotes to the engine?
something is not right , its probably simple, but i fail to see what .. . .
Customer: replied 1 year ago.
tried pumping the fuel, made no effect, today built the revs very slowly to 3600 but still a fair way off planing the boat.

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