Hi,
I have a 1990 Larson All American 170 with a Mercruiser Alpha One 3.0L engine and Mercarb carburetor.
It's been neglected for a couple of years, winterized without fuel stabilizer & half a tank of old fuel. It was running pretty rough, but after a can of paraffin/hydrocarbon based carb cleaner in the tank, adjusting throttle cable slack, and new fuel, its been running close to perfect.
The problem is that after more than an hour, I lose top speed at from about 3/4 to full throttle, with continuous bogging/surging symptoms. Going from idle to full throttle too fast can on the odd occasion give a carb backfire.
The engine doesn't seem to be overheating, thermostat gets fairly quickly to 150 and never goes higher. While in this problem condition, running from idle to about 2/3 wot still feels completely smooth and normal.
Before taking the carb apart i'm planning to check all the fuel filters, and check the fuel mix (maybe too lean?). If that doesn't improve matters then I guess I will be looking at blocked jets etc.
Would be glad to hear from more experienced folk here if i'm on the right track.
My feeling is that if the fuel starvation was due to filters blockages or accelerator pump issues I would expect to see the problem when cold also - I guess I don't understand the reason for the problem to occur only after extended use. Since the engine reaches operating temperature quite quickly, what else is happening to cause this effect?
I have a 1990 Larson All American 170 with a Mercruiser Alpha One 3.0L engine and Mercarb carburetor.
It's been neglected for a couple of years, winterized without fuel stabilizer & half a tank of old fuel. It was running pretty rough, but after a can of paraffin/hydrocarbon based carb cleaner in the tank, adjusting throttle cable slack, and new fuel, its been running close to perfect.
The problem is that after more than an hour, I lose top speed at from about 3/4 to full throttle, with continuous bogging/surging symptoms. Going from idle to full throttle too fast can on the odd occasion give a carb backfire.
The engine doesn't seem to be overheating, thermostat gets fairly quickly to 150 and never goes higher. While in this problem condition, running from idle to about 2/3 wot still feels completely smooth and normal.
Before taking the carb apart i'm planning to check all the fuel filters, and check the fuel mix (maybe too lean?). If that doesn't improve matters then I guess I will be looking at blocked jets etc.
Would be glad to hear from more experienced folk here if i'm on the right track.
My feeling is that if the fuel starvation was due to filters blockages or accelerator pump issues I would expect to see the problem when cold also - I guess I don't understand the reason for the problem to occur only after extended use. Since the engine reaches operating temperature quite quickly, what else is happening to cause this effect?