1988 mecury 135hp bogging out

keswick

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Joined
Mar 20, 2003
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3
I have a mercury 135hp outboard on a sea ray seville. I use it mainly for skiing. 2 years ago the engine over heated and many new parts were obviously fitted. Since then I have struggled to get top end performance and will not get past 3500 -4000 rpm. When being pulled it struggles to pull me up and then the throttle must be fully down to reach a speed which is ski-able. Occasionaly (once/twice a season)I get massive rpm 5500+ at 3/4 throttle, possibly due to no mixture occuring and getting just fuel. Occasionly the performance will increase for maybe 2/3 outings and then drops off again. I have just recently replaced the carbs. It has been suggested that the coils may be bad, or that the carbs need re-setting. I'm losing paitence time and money with this motor. Any suggetions please? tc1topcat@hotmail.com
 

Kenny Bush

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Mar 24, 2002
Messages
564
Re: 1988 mecury 135hp bogging out

Keswick, I would decarb that motor and then run a compression check to see how good the powerhead is. If the powerhead compression is good and balanced in all cylinders, I would move to the fuel situation. Check the compression on all cylinders and post results.... Goodluck.......BushCat
 

keswick

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Mar 20, 2003
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Re: 1988 mecury 135hp bogging out

Thanks for your reply. Compression test has been done and all cylinders are good!
 

Kenny Bush

Chief Petty Officer
Joined
Mar 24, 2002
Messages
564
Re: 1988 mecury 135hp bogging out

Well, since you put on new carbs, and it works fine 2 out of 3 times, I do not think carbs are gummed up. So I would move to ignition....and yes you could be dropping a coil.... does your tachometer jump at all during this problem? Does it do this 1st off the trailer, or after the motor heats up? Can you tell if you are using 2 stroke oil out of the oiltank? Plug wires are all on firmly? Check it out and post results.....Goodluck....BushCat
 

keswick

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Mar 20, 2003
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Re: 1988 mecury 135hp bogging out

No the tachometer does not jump about. If it's going to do it it does it straight off the trailer and won't improve. I am using oil. The wire are firmly on but may need replacing. Fuel tank leaks if filled fully!
 
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