westwind77

I picked up a RTR Prather Commander II from an old hobby shop that found one new in the box in the back room covered in dust for a decent deal. It has the Zenoah 26 w/ clutch. Running 94 octane ethanol free fuel with redline oil at 16:1. Test started everything at the house. Put it in at the lake and everything seemed fine - taking it easy for break in running the shoreline when it suddenly died. Took a little bit to retrieve it but got it back and looked things over and could not 'see' anything wrong. Primed/choked and pull started it again and let it run in idle to confirm water was flowing through the water pump (which it was as it was coming out the wet exhaust). Ran it a little slower this time back and forth and about within the same time it died again. I put it back in the truck and cleaned up. After about 5 or so minutes went to close the back of the truck and could hear a 'hiss' noise from the boat. The 'hiss' was air trying to get into the fuel tank, when I cracked the top you could hear it suck the last bit in. Could the vacuum in the tank be the reason for the stalling as it could not pulled the needed fuel after a bit? By the looks of the cap these tanks are sealed tight and vent through one of the 2 tubes coming from the tank. Being new these tubes are clear and free (from the quick look i did). The engine did not feel too hot and stock I doubt the carbs are out of adjustment as it idles perfect and runs through the full RPM range without the slightest hesitation. If someone has any ways I should check the fuel vent system please let me know (or any other thoughts).

Thanks!

w3bby

Vacuum in the tank will stop the engine. If you heard it wheeze when you opened it then you need to check that the tank is venting properly. Not the nicest way but suck on the feed to the carb, empty the tank first or you could get a nice sip of fuel.... YUCK!!!

danielplace

Put a water or pressure fitting in the cap and piece of tygon fuel line and run it into a small canister like a film canister with the end stuck in a piece of oiled airfilter($3 lawn mower part)foam inside. Be sure to make a air in hole away from the end of the tubing. This lets it breathe but keeps water out if you flip.


Be sure you have plenty of good flotation in the hull and on anything that can come off the boat.

westwind77

I read something about the stroke having to line up with the vent to properly vent, guess I will ready up on that more if for some reason the tube is free after I test it.

I had to read that a few times but then it all clicked. Very interesting/easy solution as well. I think that will be my Plan B if I cannot find the vent problem.

Ron Olson

My Feedback: (1)

You've been told the problem. It's very common in gas boats using tanks even with newer Ready-To-Run gas boats.
A lot of us have switched to using IV bags. They're lighter, won't get water in in case of a dunking and collapse as they empty so no venting is needed. If you have a primer carb you won't need the return line. If you have one now, just pull the line off the carb as that'll help to vent the tank.