help with merc 9.9 - revs and load

[chuss]

hi everyone.

Need some help with a motor issue.

I have a 9.9HP 4 stroke Mercury outboard.
When using the motor out of the sea, ie in the driveway washing it, or in a tub of water - in gear or idling, the motor gets full revs.
However, when under load, ie in the sea.. In gear only under load, it only gets half revs., ie only getting half speed

Any ideas as to what's causing this??

[Blackened]

G'day

How old is the engine? What changes when on the water? is the fuel tank in the same area, the same fuel and the same location (kinked lines)

Dave

[dreemon]

Does it sound like it idles different? maybe one plug isn't firing, being a 4 st it prob isnt going to be affected by old fuel, Or like Blackened said, restricted fuel supply,

something you can try is to get it on the water and get it going as fast as possible and pull the choke a few times, that can clear a simple blockage by using the engines vacum ,

[oldboot]

sound like it isn't correctly proped.

cheers

[Noelm]

OK, you need to do a couple of very simple things first, I assume it used to be OK! so, without the motor running, does the throttle fully open? next is the manual choke partialy stuck/jammed on? pull the plugs, do they all look the same? replace them anyway, they are cheap and easy, next important thing, DO NOT REV it up in neutral!