350 magnum mpi mysterious failures

[bandit86]

Re: 350 magnum mpi mysterious failures

no O2 sensor??? why not, that's like the best way to keep your air/fuel mixture right..

 

[rodbolt]

Re: 350 magnum mpi mysterious failures

no O2 sensors, yet.<br /> yamaha tried them with varying sucess on their EFI and some HPDI 2 strokes. they become contaminated easily by oil and water vapor.<br /> same with catilytic converters. we dont have them,yet.<br /> however its under development.<br /> but as most boats run at or near WOT most automotive systems will be in open loop mode.<br /> the draw back to running at or near WOT in closed loop is if the sensor has an inrange malfuntion the ECU wont detect it but will lean out the fuel and create issues.<br /> it happens with the OX66 motors rather frequently due to lack of sensor maint.<br />and the sensor from yamaha is close to 360 dollars I think.

 

[bandit86]

Re: 350 magnum mpi mysterious failures

exactly what i thought was happening... makes sense. Wouldnt an O2 sensor hooked up to a gauge be not a good investment, it would not affect your ecu, but would give you an idea of what is going on inside your engine? Or at least an exhaust temp gauge?

 

[ljc cox]

Re: 350 magnum mpi mysterious failures

Hi everybody!<br /><br />Well the phone calls fly back and forth. Sea Ray wants to just put a new longblock in and test it. I say they've already tested it till they were blue in the face and finally told us all was "normal". <br /><br />So - Here's my question???? The port engine has about 100 hours on the longblock under the same probable overprop situation. If we open it up to look at the combustion chamber, will it show signs of excessive combustion temperature by now?????<br /><br />Mucho thanks!<br /><br />Laura

 

[Buttanic]

Re: 350 magnum mpi mysterious failures

Reading spark plugs will tell you a lot about combustion chamber operating conditions. It will tell you if detonation is taking place.

 

[ljc cox]

Re: 350 magnum mpi mysterious failures

Well guys,<br /><br />I kept pushing and Sea Ray paid to open the port engine. After only 100 hrs (it was replaced last year) it was completely destroyed inside. I pushed harder, Sea Ray sent out their field tech, he inspected further and discovered the manifold gaskets had probably been leaking from day 1 on both engines. At least, that's their story and they are sticking to it. Sea Ray is sending us two NEW Horizons ( our request) with 5 yr warranty, new drives and will ensure we have the proper propellors. They are covering ALL costs associated with this.<br /><br />Thanks for all the help! The info you gave me was very helpful.<br /><br />Sincerely<br /><br />Laura

 

[Don S]

Re: 350 magnum mpi mysterious failures

That's good to hear. Can't really understand how it could be a riser gasket problem on 2 engines, but that shouldn't be a factor with the new engines. You will now have the "Dry Joint" type exhaust system. Should eliminate any chance of getting water in the exhaust from the manifold/riser joint.

 

[ljc cox]

Re: 350 magnum mpi mysterious failures

Yeah, I don't really care what their excuse is, just so it gets fixed!>>You will now have the "Dry Joint" type exhaust system. Should eliminate any chance of getting water in the exhaust from the manifold/riser joint.>> That's why we asked for it!<br /><br />Best to all<br /><br />Laura

 

[Uniflite32]

Re: 350 magnum mpi mysterious failures

I wonder if the "real" problem was water injestion that any late model (Gen IV I believe) 350 is known for. Due to valve overlap any Merc, Crusader, Volvo, etc 350 (and 454's from what I understand) will injest water if idled for extended periods of time. (30-40+ minutes) <br /><br />They made a manifold change in 2005 I believe that resolved this. If I idle my 2001 Merc Horizons more than 20 minutes or so I pull one out of gear and run the RPM's up to 2000 for a couple of minutes to expel (or burn off) any water that might have accumulated in the manifold cavity. <br /><br />I've had several oil analysis done on my motors and so far at almost 500 hrs I've had no problems. I'm propped to turn 4950 (30.4 KN) on my 32' Uniflite Sport Sedan.<br /><br />Did that SeaRay spend a lot of time idling?