83 Mariner V-6 Magnum - Won't throttle up

Posted last summer about re-building this engine due to a burnt up piston. Since then the engine ran well, except it was slow to get from idle to full throttle rpms. If I punched it all the way down, it would hesitate, sometimes for over 30 seconds, and then it would run up to full rpms. After that, it would run well.

I decided to run some carb cleaner through it to see if that helped. Used cleaner that mixed in the fuel. I ran the boat for 30 minutes at @ 85% throttle. Then I came to an idle only section of the lake and had to idle for 10 minutes. When I left that section, it still ran fine, but would not throttle up above idle. If I held the throttle down all the way, it continued to run and felt like it "wanted" to rev up, but it would not. Eventually it would stall.

This is what I have done so far:
- replaced the fuel.
- replaced plugs and checked each piston to be sure they were firing.
- rebuilt all three carbs
- checked all fuel filters to see if they were restricted.
- checked the fuel pump for obstruction by squeezing the bulb and got good flow.

I really don't know what to try next. When the engine is running, I can sometimes get it to rev up to 4500rpms in neutral, but in gear it just does the same thing as before. Sometimes I can get the engine to "react" by hitting the choke, but it does not ever get up above idle.

Is it possible the fuel pump is not working to push more fuel when I throttle up.
Any help would be greatly appreciated. I really can't afford to leave it at a mechanic to work on.
Chieftain

Re: 83 Mariner V-6 Magnum - Won't throttle up

It could be the fuel pump, try squeezing the bulb when you are trying to get it powering up and see if that helps.
Can you check that your timing is advancing in neutral?

Re: 83 Mariner V-6 Magnum - Won't throttle up

Tried pumping the bulb today while revving the engine and nothing happened. It made no change at all. I have ordered a gasket set for the reeds and reed block. When I rebuilt the power block last summer and then the carburetors recently, I have now virtually replaced all gaskets with the exception of the reed block. I am also going to rebuild the fuel pump just to be safe.
I am thinking now that it might be electrical, but that does not make much sense considering it did not start doing this until I ran the carb cleaner through it.
You asked about checking the timing advance in neutral. What do you mean? My am only a mechanic in that I can take things apart and put them back together with the manual. When it comes to actual understanding of how it works, I am pretty naive.
Chieftain

Re: 83 Mariner V-6 Magnum - Won't throttle up

Timing is critical to make power.

Disconnect the throttle cable and watch the throttle arm and timing lever move together until it reaches maximum timing, from there on only the throttle arm moves until the carbs are wide open.

Did you notice the initial throttle movement allowed timing advance only as the air gap closed to the throttle roller on the carb linkage?

Idle speed is adjusted with base timing which is often ATDC, timing must advance to BTDC as the carbs open to make good power.

Make sure the timing lever is moving smoothly all the way from idle to max timing.