Logo
FULL SITE MENU

LZ300TXRD Help plz

S

S61TrunkMonkey

New member
Hello Everyone, a quick introduction here. We are a military family boating on the Pamlico River in NC.

We picked up a used Yamaha LZ300TXRD got it mounted to our custom built 33ft pontoon boat and we have had some fuel issues. The engine will run fine at idle, and also with choke. Once the engine is under a load it will run great for about 2-3 minutes and then runs rough, if you reduce the throttle to idle, the engine dies. If you let the engine keep going (running rough) with reduced RPMs, the engine will eventually recover and go back to normal for a few minutes, and then run rough again. If the engine cuts off from running rough, We have a hell of a time getting it to restart. Every now and then with the engine running perfect it will stall / surge / recover in the higher RPMs, like someone going 25mph and chops the throttle to idle and then slams it forward to power again. We have also noticed, if you let the boat sit 1/2 hour, the boat will restart perfect and run fine, until it decides to have issues.

So far we have....
* Changed the spark plugs
* Changed the VST filters and fuel pump and screen inside the tank. Replaced the VST tank seal.
* Changed the fuel filter on the side of the engine
* Changed the fuel / water filter in the transom.
* The fuel system is new ( Newly built custom boat) New- Tank, fuel sending unit, primer bulb, vent hose, fill hose, fuel pick up straw, hose to engine.
* Tested the 2 mechanical LP fuel pumps - Both check fine, replacing them anyways.
* Changed the fuel filter above, but mounted to the VST.
* Fuel tank vent line is not blocked or crimped, and the fuel line to engine has no kinks.

Anyone have any solid advice? I am stumped!
 
*Update*

I hooked it up to some water in the driveway, it started up fine, but is idling rough bouncing between 600 and 1200 RPMs and will finally bottom out and die.

Coils and fuses tested fine.
 
Mystery filters, O-rings for the injectors, and thermostat with gasket on order. I also ordered an ultrasonic cleaner for the injectors and fuel pressure regulator. I will report back.

Anyone have any other ideas?
 
I am closer to understanding the problem. I hooked the engine up to some water in the driveway, the clear filter bowl on the side of the engine will be full after priming or sitting. Once I start the engine the fuel sucks down half way down to the bottom of the filter and then the engine dies. After the engine is off of 1 minute or so, the fuel fills back up in the bowl and the engine restarts. I am assuming at this point one of the LP pumps is not working, despite passing the test of loosening from the engine and priming the fuel bulb? Asking for a sanity check- Is the filter bowl always supposed to be full?
 
Back
Top