Won’t pass 4500 RPM. 70TLRA

Cleaned carbs at beginning of season. Boat ran at 5700RPM with 2 people.

Ran fine for about 30 gallons, then wouldn’t pass 3400rpm. Pulled air cover and saw no fuel from middle carb.

Removed and cleaned carbs again. Found main jet on middle carb was clogged, probably came from internal fuel lines. Makes sense.

Put them back together and now it won’t pass 4500RPM. Even with 1 person on board. And fuel consumption is over 10GPH.

Ive noticed fuel/oil in the carb throats after it sits tilted up.

I did my best to get carb adjustments back to factory, I.e. 1 - 1 1/2 turns out.

Does this sound like a carb float issue, or something else?

When you discovered the 1 clogged jet did you at that time pull and clean the other jets? Makes sense that if 1 is clogged so too others cud be.

If your seeing small amount of oil in carb throat after motor was stored tilted up this isnt too much for concern. Excessive amount indicates one or more of the oil feed tubes has bad one-way valve.

ClassicAQ said:

When you discovered the 1 clogged jet did you at that time pull and clean the other jets? Makes sense that if 1 is clogged so too others cud be.

If your seeing small amount of oil in carb throat after motor was stored tilted up this isnt too much for concern. Excessive amount indicates one or more of the oil feed tubes has bad one-way valve.

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Yes, all 3 carbs were pulled and cleaned at that point. I would consider it a small amount of oil in carbs.

I replaced the fuel pump this afternoon. The old one had a huge hole in the diaphragm.

It runs MUCH better now. Got right up on plane. 5700RPM wide open throttle.

But its still not perfect. It will only run at 5700 for a few seconds, before going back down to 5000 or lower. If I let off the throttle for a few seconds I can get it back to 5700. But again, that only lasts a few seconds. Feels like it can’t get fuel fast enough.

Fuel line is new. Filters are new. Fuel pump is new. Carbs were just cleaned.

That leaves the tank and the internal fuel lines. The tank is portable.


Does this sound like the carb screws are just out of wack? What about a coil pack working intermittently? Light up spark tester shows spark.

Thanks for the help

No, air screws (aka mix screws) have a predetermined fuel/air ratio that cannot be altered by turning in/out screws. So this wouldn't be the cause of dropping rpms. But it does sound fuel related. I wouldn't give up ruling oit that system yet. How about the primer bulb....if possible, loosely wrap your hand around it as you throttle up to WOT and pay attention to how the bulb reacts...standard full or does it collapse?

If you've a restriction btwn tank and bulb then it will collapse. Another troubleshooting test is to squeeze bulb as engine drops rpms. If engine responds w/increase in rpms then this issue is def fuel related.