Mercury Year 2000 75 h.p. 2 stroke 3 cyl.

[nitetime]

I bought this boat used about 5 years ago been running ok. So last year my motor started to act up. Hard start but good on higher r.p.m.'s 1000 r.p.m.'s and up was ok. So this year I did some tlc. New impeller, new voltage regulator, new spark plugs, new fuel pump, fuel filter and lines with primer bulb fresh gas new carb. gaskets. Cleaned carbs. but still have same problem. I took carbs. off and measured the floats. they where where off by about .100" so I set them to 9/16" per the manual and idle screws to 1 3/8 turn out per manual. Manual say's from 7/8 to 1 3/8 turn I took the kids skiing to the lake and it ran good for about 3 day's then same problem. Tried to adjust carbs. at lake and no change Now I am back to the same problem. I sprayed some carb. cleaner on the butterfly shafts and get the r.p.m. to jump just a little maybe 100 r.p.m.'s,. Spark plugs and spark looks good. I think someone put the wrong floats seats in the carbs. So the carbs. are going to cost me about $800, carb kit is going to cost me about $100 and if a coils are bad its about $400..

If my carbs. are bad why did it pull skiers for 3 day's and not miss a beat.

Question is am I missing something before I throw money at this thing?

Any input would be appreciated.

Thanks

 

[ThomW]

Have you checked for spark on all 3 cylinders?
Why do you think you need new carbs? What is your basis that someone put the wrong parts in your carbs?
I'd check for spark first. Then I would work on gas and carbs. Did you soak the carbs really good? It doesn't take much to gum up a low idle jet on those carbs. I would try tearing them down, cleaning them thoroughly, and rebuilding them before I just assumed I need to buy new ones.

 

[racerone]

Start with a compression test , post the numbers.-----There should be no reason for spending beer tokens on new carburetors !-----Is oil injection in service / bypassed / oil output tested ?----Time to do some simple trouble shooting.

 

[nitetime]

Thanks for the reply,

Sorry compression test all 3 cylinders where at 90 p.s.i.. I unhooked my gas line from the inboard boat tank and ran right from a can of fresh gas for a while and the motor did not run any better so I crossed off the bad gas in the tank idea. On the ear muffs the its hard to get the motor to even run without revving the motor.

Floats-- to get to the 9/16" measurement I had to bend my float tabs about 20 degrees. I never had to adjust a float that far before. I wish I new what the over all measurement was for that carb. so I could measure mine. I know $30 and I could just replace them.

I was taught years ago that if an engine is sucking air from place, spray a flammable liquid, or propane gas. around the engine and if the r.p.m.'s go up that is where your vacuum leak is and my carbs are might be leaking just a bit.

Thanks

 

[racerone]

Well-----You should never have to do these wild alterations to floats.----Something is wrong with you float adjustment procedure !

 

[nitetime]

I did it because I needed the boat. Now its time to figure out which way to go. I think I am going to get a carb. kit. I was just on Amazon and they called one a sierra replacement kit and it was cheap, looked deeper and its a off brand kit with bad reviews. Not a seirra.