merc 80 hp thunderbolt dies when opened up

[iaincwil]

it runs on tick-over fine and goes crazy with the start lever opened but when its in gear it will only run at tick-over if I try to accelerate it just dies,
anyone any ideas why the small lever at the side opens it up and it races away but wont when its in gear,
if I open it up by hand OK accelerates ok just when I put it in gear.
Mick thanks
mick

 

[iaincwil]

Re: merc 80 hp thunderbolt dies when opened up

have tried squeezing the bulb whilst accelerating no-go

 

[PuckHog]

Re: merc 80 hp thunderbolt dies when opened up

Had same problem with my '78 Merc 800 80hp w/ Thunderbolt ignition. Don't rev motor when not under load (not in gear) to prevent 'runaway revs' and potential internal damage. Keep no-load revs to ~2000rpm and less. Back on subject, I cleaned fuel system, rebuilt fuel pump, broke down and cleaned carbs, reset floats, de-carbed, and did the 'link and sync' procedure as laid out by Clams (use search function). Made a world of difference and motor goes like a scalded dog- most of the time. I also have corroded wires coming from my trigger which is another story altogether. But, I had to move through the above to get to the point of examining the wiring.

 

[iaincwil]

Re: merc 80 hp thunderbolt dies when opened up

whats the triger (accelarator) there is a junction box on the right hand side looking from the rear and there are some corroded wires out of there, where else should I look.
mick

 

[PuckHog]

Re: merc 80 hp thunderbolt dies when opened up

That is the CD ignition switch box and the wires from the trigger indeed connect to it. Before messing with any of that (all ignition components are either expensive, extremely expensive, or unavailable) please buy a manual.
I would also be inclined to perform a compression check, followed by thorough fuel system cleaning and adusting, and finish up with a 'link and sync'. If the problem persists, only then start testing the values of your various ignition components and integrity of the wiring.

 

[PuckHog]

Re: merc 80 hp thunderbolt dies when opened up

The trigger is a series of magnets on a ring inside the stator under the flywheel which uses induction to 'trigger' the coils and plugs. You'll need special tools to service the trigger (and a manual)

 

[iaincwil]

Re: merc 80 hp thunderbolt dies when opened up

think I will consult the w/s manual to find out about that,
ah! the black box thingy that replaced points yes I know it well!!!
a compression check mmmmmmmmm!!! well it just had a service at £400 and they were supposed to have done that but dont think they did anything the blessed thing come back worse than it went in, all they did was move the battery from in the cabin to under the transome and shortened the cables that cost £400
think I will become a marine engine machanic I must be able to do what they did and for that cash I would LOL!!!!!
anyone else more ideas
mick