'98 C40TLRW (2 stroke) Starting Issues

[dltruong]

New user, first time poster here!

Recently acquired a boat that has a 1998 C40TLRW (2 stroke) motor on it. Lately, I have been having issues starting the motor; initially, when I first launch the boat and also throughout the day, after long periods of sitting in one spot.

My startup procedure is simple: open up vent on gas tank, pump bulb until it is firm and start the engine.

The issue I am having is that the engine will start and rev high for a moment before settling down but then seconds later, the motor cuts out. I go through this process about 5-6 times before the motor will stay on and idle and I can start moving again. Once the motor is running, it runs fine (at low RPMs to WOT).

I'm not sure what has or hasn't been replaced or cleaned in the past. When I first got the boat I did the basic maintenance on it: new spark plugs, new water impeller, changed lower unit gear lube, new thermostat and replaced external anodes.

I use all Yamaha products and mix Yamalube at a 50:1 ratio and 1 oz of Ring Free per 10 gallons of fuel. At the end of each trip I flush the engine and run the motor dry (by disconnecting the fuel line from the motor as directed in the owner's manual). I also inspect and clean my spark plugs and I clean the fuel filter and inspect the fuel for any debris or water after each use.

My first thought is that there is a problem with the fuel delivery system. So I am thinking of replacing the fuel line and primer bulb and the fuel pump. I may also replace all the rubber hoses feeding the carbs as they all seem "soft."

If this does not fix my issue then my next step would be to clean/rebuild the carbs as I am pretty sure that has never been done.

Please, any insight/comments/suggestions would be greatly appreciated!

Thanks!

[wildturkey]

Sounds like you are not choking it intermittently until it warms up. I have a choke switch that I keep turning on and off until the idle stays at a decent rpm. At the same time I try to keep the rpm at 1200 until it warms up.

[rodbolt17]

you can push the choke till the switch falls off and nothing will ever happen, its a prime start model.
rather than dealing with the fuel system piecemeal simply do it all at once.
takes about 2 hrs or so.

[99yam40]

you have a prime start enrichment system on this motor.
It advances the timing and adds extra fuel during cold start.
Temp switch tells it when motor is warmed up to change timing to normal (could be this is faulty)
the voltage from lighting coil to the Heater unit closes needle as the motor runs.
Sounds like it might be a problem with passage plugging and is not enriching during cold start , pilot circuits are plugging, or carbs are not adjusted properly.

I would pull carbs and clean everything up and check all passages.
Follow service manuals procedures for checking needle in prime start and the link and sync after reinstalling the cleaned carbs