Blew my yamaha 3.1 225 engine. Need help.

[vmax225]

Well I was having this problem for 2 weeks now. At high rpms the engine would start to get weak then come back to life like it was lack of fuel pressure, but not really for sure now since I blew the engine. At about 4k rpms it just clicked and that was the end. I pulled spark plugs and one sparkplug was melted. So I looked into the cylinder and seen there was have a piston left. So then I pulled the cover off and seen that one piston detonated and melted to the wall. Also there appears to be a small whole on the wall at the bottom of the powerhead. Not sure how bad yet but its not soposed to be there. So now the powerhead is ready to come off and I am sending it to a machine shop that I will have weld the whole shut and then clean up the wall. Is this a good idea or not? Or do I need to resleeve that cylinder? Also How much is just 1 new piston and were should I get it at? The rod appears to be fine but I will have it checked. Anything else I need to do besides this? Im a certified auto mechanic not a boat mechanic so I really dont know much about them. I just really dont want to pay 4k for a new powerhead.<br />Please help, <br />Thanks. <br />2000 yamaha vmax 3.1 225 fuel injected.

 

[mzmanley]

Re: Blew my yamaha 3.1 225 engine. Need help.

VMAX - along with the advice and recommedations provided here you may also want to tap the resources on the bulliten board below:<br /><br /> http://pub165.ezboard.com/fbbcboardfrm11 <br /><br />I've been reading the posts on this board and and a lot of commentary on VMAX motors. Good luck

 

[jim dozier]

Re: Blew my yamaha 3.1 225 engine. Need help.

Based on your history and description, your engine melted down because it was running lean. Probably due to a clogged carb/injector or faulty fuel pump. When they run lean they detonate. When they detonate, well they do what you have. Regardless of how you fix the piston/cylinder/cranks you should fix the root of your problem (fuel system) before you break the rebuild back in. You don't say whether you were on oil injection or premix. If you were on premix and you were running lean you were running lean on lubrication also and I would take a long careful look with a micrometer at your crank journals also. Apparently from what I read on these forums, your can overbore single cylinders (oversize pistons are calibrated to the same weight as OEM pistons) if you can confirm damage to only 1 cylinder. What caused the hole in the cylinder wall, are you sure it isn't one of the ports?

 

[rodbolt]

Re: Blew my yamaha 3.1 225 engine. Need help.

Hello<br /> not knowing the maintenace history I will ask. when was the VST filter last serviced? when was the last fuel pump rebuilds? and when was the last o2 sensor cleaning? has the motor been updated to the latest o2 sensor draw tube? if this motor has its regular 100 and 200/annual maint they go a long long time. if not they like to munch on metal. dont let a standard automotive shop do the work. most cannot properly chamfer the ports or even know that they have to be chamfered. what you described sounds like it was leaning out. either the fuel could not get to the vapor seperator tank or the high pressure pump filter is clogged. also while it is down change the water pump t stats and pressure valve grommet.I would suggest buy a clymer type manual as the factoy manual is rather technical and leaves out some details. just make sure you dont traet this like a car engine<br /> it is most definatly not a car engine. if the cyl to wall clerance is to large on a car engine it may consume more oil. it it is to large on a two stroke it will blow hot gas past the rings and cause carbon and contamination of the incoming air fuel mix.I am sure that somewhere there is a place to send the injectors out for testing<br />I just have had no recommendation from yamaha. this engine has tighter tolerances than anythig automotive ever built. follow them exactly or it will fail again.<br />Good luck and post more info. the 3.1 was and is a good engine. the maintenace is critical

 

[vmax225]

Re: Blew my yamaha 3.1 225 engine. Need help.

Thanks for all the info. I figured it was a fuel problem for it to detonate like that. But never got a chance to put a fuel pressure gauge on it while running the engine. It is oil injection. I plan on testing the injectors through a local shop. The fuel pressure will just have to be tested once I gte it running again. I will jsut have to be careful. Were can I get a sleeve If it is needed?

 

[vmax225]

Re: Blew my yamaha 3.1 225 engine. Need help.

And about the whole in the wall it isnt one of the ports it is underneath the piston at the bottom. It look to have jagged edges so I am assumming it wasnt there before. I will keep you guys updated once I get the powerhead off.

 

[marinegrh]

Re: Blew my yamaha 3.1 225 engine. Need help.

there is a local company in jacksonville that cleans, and rebuilds fuel injectors on all marine engnes, i/o and outboards, if you need info you can email me at marinegrh@bellsouth.net. the cleaning process tests the electrical and mechanical side of the injector, back flushes the the injector, installs new seals filters and o rings, for around 35 a piece, that beats buying new at over 150 a piece and will even do a spray pattern test to ensure full cleaning