2003 Yamaha 225 EFI, Lower Unit Picture!

[KCLOST]

This is a pic of the lower unit described above. The motor is mounted on a 2003 Triton TR20. It is mounted 6.5" above the transom which also takes into account an 8" detwiller jack plate that is on there.

I have had the motor running for about 10 hrs, and at WOT for about 3 hrs...

The mechanic at my dealership says it is a "cavitation burn"! Regardless of what he says I want your opinion!!! I've never seen that before!!! I should add that the lower unit looks much better than the picture shows with the exception of the spot in question. There are no other paint problems. But that burn or bare spot is actually down to bare metal in about a dime size area that you can't see in the pic. The other side looks about the same but it is about 25% smaller in size.

I am running 18 psi at WOT and about 70-75 mph...
It is still under full warranty for two years.. Haven't hit anything to cause this.

Thanks in advance...

 

[rodbolt]

Re: 2003 Yamaha 225 EFI, Lower Unit Picture!

thats what it looks like to me. looks like cavitation is burning off the paint.
not a lot can be done other than set the engine up the way it was designed or keep painting it.
you may wish to contact Bob's machine and see about having your case modified for low water pick up and have the bullet and leading edge smoothed and reshaped.
yamaha reccomends the cavitation plate be 1" above or below the hull. your running a stock case at way higher than reccomended heights.
the leading edge needs tweaking to prevent the air bubbles from forming and collapsing and eating the paint then the metal.

 

[KCLOST]

Re: 2003 Yamaha 225 EFI, Lower Unit Picture!

So continued running can eventually eat the metal away also?

What kind of cost am I looking at to modify the leading edge only?

By the way, the motor/boat is set up per Todd Morgan with Bass Boat Central...

 

[Ray Neudecker]

Re: 2003 Yamaha 225 EFI, Lower Unit Picture!

It is a cavitation burn, not uncommon where stock gear cases have been run high. I know of no lasting damage it will cause. The transom saver marks don't help.
Stripping the pant off, rounding the front of the housing and smoothing the housing, as well as using only a primer may help.
All of the above may show a slight improvement in speed, but it is not an uncommon or major problem.

 

[KCLOST]

Re: 2003 Yamaha 225 EFI, Lower Unit Picture!

To me it looks like that cavitation burn is very much in line with that lower groove that guides water into the intakes...

I'm not sure if the front of the lower unit is the cause as much as that groove that angles upward at the bottom of the intake.

Ray, The transom saver marks are not as bad as they look in the picture... The flash on my camera makes it looks like paint loss, but they are only smudges....

 

[rodbolt]

Re: 2003 Yamaha 225 EFI, Lower Unit Picture!

over time the burns will eat into the aluminium, with Rays mods you may grab a bit of speed, with a modified housing maybe as much as 4MPH. those burns are indicative of very uneven water flow(pressure) acrossed your case.
smooth out the flow and the case slips through the water even better. last one we sent down was about 500 dollars, however they place the upper water lines dead in line with the oil vent plug making oil changes interesting.
may be worth a phone call to Bob's machine.

 

[Ray Neudecker]

Re: 2003 Yamaha 225 EFI, Lower Unit Picture!

We have the low water nose cones put on by Props Plus in Tuscumbia, Ala. He plumbs the water through an enclosed pipe and you can get to the oil drain and pull the gearcase without a struggle as well as looking 100 precent better than Bob's for about the same money. The grates for the water pickup are partially to blame for the burn.

 

[KCLOST]

Re: 2003 Yamaha 225 EFI, Lower Unit Picture!

Ray,

Do you have a web address or phone number for them?

Thanks

 

[KCLOST]

Re: 2003 Yamaha 225 EFI, Lower Unit Picture!

I took a closer look at the intakes last night... On both sides the plastic intakes are sticking out just slightly farther at the bottom compared to the rest of it...

I removed them and sanded them down slightly with a fine file. They are now recessed evenly across the entire surface...

Will do some testing this weekend.