1982 Chrysler 75hp loses power

[newboatrider]

Hello to all, I just bought a 1982 75 hp Chrysler outboard that came with a boat, I cleaned the carbs really well and used a marine tank that I already had that uses the same mix of fuel which is 50:1. I can get the motor to hit full throttle for about 5-7 seconds, then it dies off or lags and only after I cruise around the lake at about 50% power can I then go to full throttle again for the about the same amount of time 5-7 seconds. When it drops out of the full power range, I can't get that performance back until a minute or two later at almost a fast idle. I have my carbs set to the owner manual standards and I follow those settings.Hopefully there is a simple fix.

 

[Nordin]

Have you chekced the fuelpump? Replace the diaphragm and put a cheap inline filter between the pump and the carbs.

With the filter you can see if it is getting fuel while running.
When it want to stop while throttle it up, try squize the primer blub. If it starts to power up then you know it is a fuel issue.

 

[jerryjerry05]

Is the tank vent open?(had to ask)
The fuel lines are 30+ years old and they might be bad??
​The carb you sure the main jet is clear?
A tiny piece of dirt the size of a pin head can clog it.
Do the filter thing Nordin suggested then reclean the carb.
Make sure the float is set right.

The needle/seat is there damage on the needle point?(rubber tip)
​The seats rubber insert smashed? (solid needle)

 

[newboatrider]

Thank you Nordin and jerryjerry05, I am going to check those carbs again with the suggestions about the needle seats and I will definitely try squeezing that fuel bulb when it does drop out of the max throttle. I will install a fuel filter between the carbs and fuel pump. To date I have replaced the fuel pump diaphragm and associated components that are part of the fuel pump, All new fuel line and clamps from the tank to the top of the carbs, new fuel vent cap with the vent open (only left it closed once and discovered that I have no leaks, it tried to collapse the tank) On the carbs, I did a very general cleaning of the bowls and spraying out the orifices that I could access without too much disassembly. This morning I will perform the squeeze bulb test with a friend and keep you posted while the boat is in operation, I will also check those seats/needles for wear and any possible debris. Thanks again, I'll keep you posted.

 

[newboatrider]

Sorry about the delay in giving an update as I haven't been able to remove and clean the main jets recently. Tried the squeeze bulb test with a friend while the boat was in motion, but virtually no response. Later today when I get back I will be pulling the main jets finally to clean them out good. I would be happy to find any sort of debris and/or corrosion in there. If it is anything like the fuel pump/diaphram prior to rebuilding it, I will be pleased.