1979 Mercruiser 120 bogs when under load

[cothric]

My boat runs great in the yard, but under a load in drive it just bogs down.
I have new coil, rebuilt carb, fuel pump, fuel filter, water seperator, plugs, wires, dist. cap., points w 22gap, button, exhaust manifold, new gas. While in the lake it will take full throtle in reverse, but in drive it just bogs down/floods. Please help, I have spents tons, but I keep thinking I have got to be close.

 

[cothric]

Re: 1979 Mercruiser 120 bogs when under load

I am new at this, am I in the right post section or does no one have any idea
on what may fix my problem. Please Help I would like just once this summer
to take my family out to the lake in a boat that will pull the kids in a tube.
thanks

 

[libellav15]

Re: 1979 Mercruiser 120 bogs when under load

OK...

take a look at the back of the boat on the inner gimbal housing - you will see where the gear change cables mount to.

at the bottom right there is an electrical switch with brown and black wires - and it sits in the dip of a 'y' shaped bracket

thats the reverse interlock switch. its only supposed to activate when coming out of gear into neutral - it kills the spark to the coil for a split second to relieve the pressure on the shift dogs in the gearbox.

when you put it in forward gear have someone look at the switch and see if it is opening and staying open - if so it will cause a stall.

if this is the case you need to lubricate or replace the cable.

another way to test is to get someone in the engine bay when you put it into forward gear, take the cable of the carb throttle linkage and operate the throttle lever on the carb by hand.

just a thought

cheers

adam

 

[cothric]

Re: 1979 Mercruiser 120 bogs when under load

Thanks for the tips, I will check this. If it continues to bog down when
you control the throtle from the carb will that tell me I can rule out
any throtle cable problems?

 

[libellav15]

Re: 1979 Mercruiser 120 bogs when under load

Hi

as you can get it full throttle in reverse I would say the throttle cable is ok

can you get it into forward gear at all without it stalling? if you can then disconnecting the throttle cable at the carb and doing by hand simly ensures that the gear select cables don't move any further and possibly hit the Reverse Interlock switch.

clear as mud right

forget the carb thing for now - just see if the reverse interlock swith is being activated when putting into full throttle forward

cheers

adam