WildSafaris

I just upgraded from twin 200hp yamaha's to twin 250 yamaha's.

This is what is happening; When I open up the troddle wide open..after about 1 or 2 minutes both engines shut down.

If I run the engines at 30mph, 40mph or 45mph they run fine.
but when I run them above 50mph they shut down after 1 or 2 minutes.

With the 200's it would run fine 55....

I have 3/8" fuel lines. Is this a fuel issue? How would I correct this?

WildSafaris

TTT

Anyone have a helpfull comment?

chad1

get some fuel pressure gauges...mechanical only gauges

Wobble

Whilst I have no experience with troddle's, it sounds very much like you are starving the motors of fuel, hopefully no harm has been done.

I would contact Yamaha regarding recommended fuel line size or just try a bigger line and see how it goes. Be sure and check your fuel filters and that the tanks are vented properly.

Pwrbt33

iTrader: (2)

Are the two new motors brand spanking new? They might have a breakin period left on the ecm. I dont know there systems very well but they might be shutting down do to over rev while in breakin mode. Kinda like Mercury's. Wont let you go over the preset rpm for the breakin period.

Just a thought.

John S.

BajaExpress

Ck your fuel tanks vent, The tank must have a good vent.

Wally

iTrader: (1)

Do you have two fuel lines coming out of the tank? or is it just one thats split into two? I would check that and the vent as BajaExpress said above...you may be creating a vaccume in the tank and the engines cant suck any fuel out...Who knows it may be as simple as a pinched vent line!
Anyway another thing to try and check is when running....is the primer ball still stay firm or is it on the verge of collapsing?
If these dont help i would try going over to screamandfly.com ...they are more the outboard guys then us here

WildSafaris

Thanks,

It's a fuel supply issue. I am only getting 40 gallons per hour out of the two 3/8" fuel lines and I need to be getting 50 gph.

The vents are all clean and the lines are not kinked. I have a 3 tank setup. Each engine has a fuel selector switch and can choose any of the 3 tanks. Each tank has 2 lines going to the 2 selector switches.

I'm thinking of adding some inline booster pumps to get my gph up. I would only need to turn them on when I'm running wide open... any comments or ideas?

Wobble

Bottleneck is most likely the fuel selector valve. I have had this problem and there wasn't a cheap solution apart from going to manual valves for each tank.

Longblockbenny

I have seen this problem when people run more than 1 fuel separator per engine and the engine pump cant keep up with the demand, also the tank outlet fitting sometimes has a spring loaded chekvalve that get a little stuck and starved the engines, normaly they have checkvalves when the boat has a generator that feeds from the same fuel line of any of the 2 engines.