1999 75hp Merc 2 stroke Power Drop

[dalton565]

Hey guys

need a little bit of advice / suggestions

i serviced the engine myself this season, done the gear oil and impeller. Also changed the prop to a larger one but it was recommended for this engine by the guy in the shop.


Anyway took her out today, she seems to be a little down on power. She pulls well at the start and planes fast. But when she gets to about 20-25mph it starts juddering, almost like its missing. You get a sudden surge of power then it goes away, then it comes back etc. The speed doesnt really drop but you can notice it by the sound of the engine. With the old prop she would hit 40 and it was alot smaller. Sorry dont have exact measurements, pitch etc.

Thought it was the fuel so tried new fuel, but still the same.

Sparks plugs where changed last year around august. Boat was fine the last time i had it out, but this was last October.

So any ideas on the issue, fuel filter was not changed so wondering could this be causing it.

Any other suggestions appreciated ?

 

[Laddies]

Re: 1999 75hp Merc 2 stroke Power Drop

Sounds like the carbs varnished up over winter and need cleaning.

 

[dalton565]

Re: 1999 75hp Merc 2 stroke Power Drop

Hey thanks for the reply, was just at the boat store, and i described the problem, and he said exactly the same thing. The carbs needed some cleaning. He said they could do it for ?120 so about $240 at today's exchange rate.

What id like to know is could you do this yourself ? What does it involve, or should i take it to a professional. i servcied the engine myself so would be somewhat handy with a spanner.

 

[Silvertip]

Re: 1999 75hp Merc 2 stroke Power Drop

I would at least look at the plugs to see if there is an issue on one cylinder as it appears you have one that drops out periodically. If they appear ok, then it tends to point to a fuel issue that is more than likely carburetor related.

 

[dalton565]

Re: 1999 75hp Merc 2 stroke Power Drop

thanks i checked the plugs they all look normal. Is there any substances that can be bought to run through the carb that might solve the issue. Its not a huge issue as you can still ski behind the boat but u can feel the kangarooing

Any ideas

 

[Laddies]

Re: 1999 75hp Merc 2 stroke Power Drop

If your mechanically inclined and invest in a manual it not a big job or you might look on the starboard side of the float bowl, near the bottom there is a plug remove the plug from each carb and clean the high speed jets, in some cases you have to remove them with a screwdriver but in others you can clean them with some spray carb cleaner. You don't want to run it hard the way it is as it is lean and could damage a piston.

 

[dalton565]

Re: 1999 75hp Merc 2 stroke Power Drop

thanks for the reply again. i have the servcie manual for the outboard which has alot of imformation on the carb on adjusting it etc. in several places it mentions carb removal but there is no section in this manual on actually how to do it. Does anyone have this in a pdf format it would be highly appreciated.

R