85 150 merc boggs down at low rpms

[CU2NITE]

My 150 runs great at high rpms but at low rpms it boggs down a bit. I changed plugs but still have the same problem. Any ideas? Thank you.<br />CU<br /><br />-------------------<br />RUNNING THE MOTOR WHILE LISTENING TO THE HORN WILL MAKE YOU MORN!!

 

[KCLOST]

Re: 85 150 merc boggs down at low rpms

CU,<br /><br />Have you checked the spark on all cylinders at idle... Maybe one of the switchboxes is causing a lost cylinder, happened to me.<br />Is your top end RPMS the same or have they gone down?<br />Will it idle ok?<br /><br />Could be the carbs also (low speed jets) but I would expect your idle to be horrible also...<br /><br />Let us know...

 

[Plainsman]

Re: 85 150 merc boggs down at low rpms

How do I check the spark at idle?

 

[CU2NITE]

Re: 85 150 merc boggs down at low rpms

Yes I'm getting spark at idle. Could this problem be due to the low rpm jets in the carberaters being pluged? Any ideas? Thank you<br />Cu<br /><br />---------------<br />RUNNING THE MOTOR WHILE LISTENING TO THE HORN WILL MAKE YOU MORN!!

 

[andy6374]

Re: 85 150 merc boggs down at low rpms

Originally posted by CU2NITE:<br /> My 150 runs great at high rpms but at low rpms it boggs down a bit.

Does it bogg down or run rough? Does it cough and sputter? Make sure the throttle shutters in the carb throats are fully closed at idle. If not this will lean out the idle mixture resulting in a rough idle.<br /><br />If all checks out, I'd disassemble them and clean em' out. Dry and blow out all the orfices and passages with compressed air. Then reassemble with new gaskets.<br /><br /><br />To answer the other question. You need an inline spark tester or timing light to test for spark. Any auto place (like NAPA) will carry these items.

 

[CU2NITE]

Re: 85 150 merc boggs down at low rpms

It doesn't cough and sputter or run rough, just boggs down a bit a low rpms. I think I will go through the carbs next. It seems like this should solve the problem due to the fact that it runs great at full rpm. Wouldn't you think?<br />Cu<br /><br />---------------<br />RUNNING THE MOTOR WHILE LISTENING TO THE HORN WILL MAKE YOU MORN!!

 

[andy6374]

Re: 85 150 merc boggs down at low rpms

We will see.

 

[tashasdaddy]

Re: 85 150 merc boggs down at low rpms

if it is just idling low, try adjusting the idle stop screw.

 

[CU2NITE]

Re: 85 150 merc boggs down at low rpms

Durring the weekend the motor started to miss and run rough at low rpms, it still runs great at rpms over 2500. Could this still be a carb problem or worse? Think I'll pull the carbs today.<br />CU<br /><br />---------------<br />RUNNING THE MOTOR WHILE LISTENING TO THE HORN WILL MAKE YOU MORN!!

 

[KCLOST]

Re: 85 150 merc boggs down at low rpms

That sounds like what it is, as long as you have good spark and compression...<br /><br />If you pull the carbs they need to be fully dissasembled and cleaned like Andy mentioned...<br /><br />Your other set may need it worse than the ones on the motor, since they have sat around so long.<br />The Carb rebuild kits are not very expensive...<br /><br />Let us know...