mariner 20hp 2 stoke not reving

[sib240]

i have a 90s mariner 20hp 2 stroke. when its in the tub it starts and revs perfetly but when on the back of my shetlnd gh 14 it gets to abour 1500 revs and just stays their does not change at all.
i have cleaned carb but has done nothing any suggestions?
thanks
rory

 

[oldman570]

Re: mariner 20hp 2 stoke not reving

Have you checked the spark of both plugs, to be sure that both are fireing. The motor might run in a barrel but not on the boat when the motor is in gear and the backpressure is on the exhaust as it should be. When a motor runs as you stated ether the high speed jet is still pluged up in the carb or the motor is only running on one cyclender. JMO
Oldman570

 

[sib240]

Re: mariner 20hp 2 stoke not reving

Okay thanks I have replaced plugs but won't be able to test it on boat to near Easter.

 

[oldman570]

Re: mariner 20hp 2 stoke not reving

You can use a timming light to see if both plugs are firing and you can buy a spark tester at the local auto supply shop usally for less than $20 to test the plugs to make sure that the rest of the electronics are working. Ether way will do the job. JMO
Oldman