I'm the one who posted the 150HP VMax "knocking" post yesterday. Worst case scenario confirmed last night. One damaged piston and cylinder. In 5 years no problems now this. I'm told my options are to either overhaul the whole thing (bore out the cylinders and replace the pistons) or replace the powerhead with a new one. I don't know which is the better option and certainly price enters the picture at this point. Any advice?

Go with the best warranty offered...check your other post

Go with a reman powerhead from Yamaha !

if its only one cyl id rebuild it ,the others would just need honing and new rings

Unless you have about $4k laying around to throw at this, I'd do what stick said. You'll have about $750 in parts and machine work. You should be able to find a qualified engine builder going into the off season that will give you a reasonable deal on the work. I bet you could get it done for about $2250 if you hit the right deal.

BTW, what caused the failure?

Artie

Rebuild 1st if possible. Secondly never re-ring an old piston, hone an old hole, or new piston an old hole. (kind of sounds like I'm talking about a woman here) If rebuilding is possible, take the block to a respectable machine shop for "mic-ing" (Measure of cylinder using a micrometer) Make a decision on the other 5 cylinders by what the machine shop says. It would be better not to re-piston old holes or to re-ring/hone or any other type of "rebuild" unless you bore the hole first. Another thing to think about is since your down already, why not for another +-$450 do all six anyway? This way you can start all over with a new powerhead and not just a patched up job. If your close to San Marcos,,,,give me a call,,,,let's see what we can do for you........(512)353-1854

1/2mann's the man, when it comes to rebuilds

Thanks again for all the help guys.

Artie, not exactly sure what caused the problem but have a good idea-and to all who read this please don't make the same mistake-I mixed the Yamalube 2M oil with their 2W oil and one day later I had the breakdown. That's the only thing I did differently. One of the oils is for personal watercraft and the other is for outboards. I believe i screwed the oil pump or filter enough to mess up the one piston. Sucks-spend prime $ on good oil to make sure this doesn't happen and still get the $5K repair in the end!! Thanks to Michael Bristow for taking me through all my options and dishing out well heeded advice. I appreciate your time today Michael. Leaning in the direction of a rebuild and told Hayden at Rockwall you had recommended them to me. They are a little farher away from my home in Corinth but I've seen nothing but good feedback from them on this site.

Also, thanks Mike for the advice. I am going to get all 6 redone. Heard that way to many times today to think otherwise. I felt the cylinders in the other 5 and only one had the very beginnings of any "roughness" but I'm sure the others weren't far behind. Only one piston had damage that we could tell.(again, I'm not the expert) If I were closer to San Marcos you'd have my boat this weekend.

I won't argue about the rebuild theories, but if I determined that mixing those 2 oils caused the problem, I would never buy another ounce of Yamaha oil. I've seen guys mix all kinds of oils in their oil tanks (I wouldn't) without any type of problems. I know that these 2 oils have different compositions for their intended uses, but there is no way that it is acceptable that they can't be mixed. What happens when you are 150 miles from home and the only thing available is the type you're not using?

On the plus side, I'm sure Hayden will find out what went south...

Artie

Artie,

We see problems all the time with people mixing oils. They tend to gel up and clog the intake screens.

However, what RKD was put oil in an outboard that wasn't designed for it.

We had another TFF'r bring in his boat not 2-3 weeks ago and thought it was overheating. What he was getting was a low oil horn. I popped the top on his oil tank, pulled the screen out, and it was so gummed up, I had to scrape it off. Drained the tank and oil lines, filled it up with the correct oil, turned the key, and presto, no warning. Never started the engine at all.

So if you mix different brands of oils, make sure you run out as much as the old oil as possible, add the new oil, then run it until it clears the oil lines. Then you should be good!

Which ever you decide I think the biggest problem with most rebuilds is that they do`nt correct what caused the problem to begine with. I would clean and reclean every little part of the fuel-oil system and replace the manual fuel pump diaphrams. Then check all cooling system components and replace as needed. If you do`nt allready have it, have the large spinn-on fuel filter-water seperator assembly installed. On and On. Good Luck

Gary, your right on. I already told him to replace the oiler, thermostats, water pump, ect. Might as well build it right.

Michael, I don't mix oils. Well, actually, I premix. I KNOW my engine is getting oil. I also know that DI engines must have oil injection. I have heard of gelling from mixing oils, but it has been a long time since I heard of a case.

I'm not convinced that rkd's engine had an oil problem. I had a ring locating pin come out of a piston and destroy one cylinder. I had to have a rebuilder determine what the problem was. He spotted it pretty quickly.

Artie

This is straight from Yamaha's website:

Yamalube� 2-W


2-Stroke Engine Oil Semi-Synthetic Injector Oil for WaveRunners� and Yamaha Sport Boats.
Yamalube 2-W was designed to provide Yamaha owners with precision-blended oil for their WaveRunner� and inboard jet-powered Yamaha boat engines. Yamaha chooses only the finest lubricants in formulating these oils.
Low Smoke
Our 2-W formula achieved an exponential reduction in smoke when compared to our previous formula for WaterCraft. In fact its performance is so good it made old Yamalube 2 obsolete. Visible smoke has been reduced by as much as 50%.
Non-Phosphorus
This oil is the only formula the factory recommends for use in YPPS (Yamaha Platinum Plus System) models. Using other oils can cause serious damage to the catalytic converter.
Rust Protection
The rust protection package was improved to provide greater protection for critical engine parts from rust and corrosion.
World-leading Lubrication
This special formula significantly reduces wear of engine components, while providing excellent lubrication for moving parts and protecting the engine from ring stick and piston scuffing.

Not recommended for land-use vehicles or outboard motors.

*Please refer to your authorized Yamaha dealer for pricing.