Originally Posted by Rage (Post 3251085)

When I make hard runs I trim the drive out under load to gain bow lift at WOT. Could that be over loading the thrust bearing? The coupler is heavily lubed with the Merc specified lube.

Originally Posted by MER Performance (Post 3252161)

You may have problems with your bearings, but if you did I feel for sure you would already have a serious problem by now. I would check my valve guides for excessive wear, side loading the guide. Who did you purchase the guides from? Are they guide liners or a full guide with a shoulder, there are cheaps ones and quality ones that are of a certified materal.
C.H.E. ,CV Products, Precision Products, are a few of the quality ones , K Line offers liners.
If you decked the block, surfaced the heads changed the cam along with rocker arms, you may have changed the contact and load pattern on the valve.

Originally Posted by 88Fount33 (Post 3251820)

I am no expert, but if the problem does turn out to be the thrust bearing in the engine, and everything else is perfect including the coupler and splines and the lubing is perfect, below is something to think about.

Fact: Going to WFO then trimming out results in the highest load transfer from the coupler to the drive input spline as you throw all the torque the engine has at the connection, even a perfectly lubed spline fit under heavy load is extremely hard to move the slight distance the shaft has to move (inside the coupler) as the drive goes up.

1) Try trimming prior to full power. (this works for me, and since I know what setting results in top speed, I just trim it there and then nail the sticks)
or
2) Apply power, increase speed, slightly back off, trim, then back into the throttle. This can be done in rapid order, as you are just trying to unload the connection prior to moving the drive. (this is what I would do if I could not trim first)

Of course, you could just fix it and then run it like you stole it and perhaps NEVER have another problem.

I like to take it easy, I must go fast, but I realize that most other boats out there are going to outrun me anyway so the few extra seconds my method adds is not important.

Originally Posted by 4bus (Post 3251799)

Rage- Are you going to tear it down?

Originally Posted by Ted G (Post 3251088)

No, but if there is too much grease in the coupler packed in at the front it can overload the thrust bearing.

Originally Posted by Rage (Post 3252390)

I thought that I saw a small hole in the end of the coupler's female splined receiver for the drive's male splinded shaft. I assumed that hole was to allow excess grease to escape to prevent hydraulic lock. Can anyone confirm this?

Originally Posted by Rage (Post 3250485)

This is the third season on the engine re build. Engine started as a stock 2004 Merc 496HO and was built to 625hp NA three seasons ago.
The crank bearings are now the Dana Clevite 77 'H' tri metal (copper and lead matrix on steel backing). The heads are the iron 496 heads with new bronze valve guides and spring loaded Vitron valve stem seals.

The first season 36 hours oil analysis was copper/lead of 13/5 ppm

The second season 59 hours oil analysis was copper/lead of 199/10 ppm but a new Hardin Marine 3x18 copper&bronze oil cooler had been installed which likely contributed (so I thought) to the spike in copper disolved in the oil from copper oxide contained in the new oil cooler.

The third season 67 hours oil analysis was copper/lead of 261/8 ppm.

Previous three seasons oil analysis was copper/lead of 10/3, 35/10, 48,16 ppm all with the same OEM bearings made of aluminum metal marrix ie no copper or lead. After the first season the heads were replaced with the current heads with bronze valve guide sleeves and the spring loaded Vitron valve stem seals.

Where besides the crank bearings can copper come from and show up in the oil analysis? I am asking this because there was no increase of lead in the oil that would be expected if the copper increase came from the bearings.