M8 drive issues behind 1350 Q4
 

Merc M8 drives not standing up to the HP of the 1350 Q4, heard merc is having issues with M8s:eekdrop:, and are going back to the #6 for reliability. Is this true, anybody else with issues with M8s.

I thought the M8 was a beefed up version of the #6? What is the difference between the two?

I believe a 35% strength increase.

It may have been just a price increase :)

The #6s make the boats faster-less drag.

The 6 is not rated for 1350hp so it wouldn't be Mercury doing this and the 1350 is sold as a motor/drive package. Im not positive whats avail today but the M8 has / had(?) limited gearing options. Some guys went back to the 6's for gear ratio selection.

The gear ratios they offer are intended to keep the speeds down.They do have a new ratio for the M8 taller than the current 1.30 and 1.43.
As to the #6 horsepower ratings-i am living proof that they do live at 1800 plus.Several M8 owners have switched back to the #6 and gained substancial top end numbers thru lower slip.

Gary, what type of oil do you run in your #6's?

...and how long can the #6's live at 1800+ hp survive on your Skater before service or major failures?

Amsoil synthetic 10w-40w motorcycle oil that Bob Teaque turned me on to.

I change oil and look for metal in oil twice a year.The main reason my drives are living is because of Vern Gilbert of West Coast drives.When he sets them up,he spends the time to check and adjust tooth contact via shiming.He gets them to have full contact evenly across the face of the gear and isnt satisfied until it does.He laps them in,assembles it,then takes it back apart till they are perfect.
His list of clients read like a whos who of boating.

That is the way it should be done. More people should try that hard :)

Mercury suggests Torco gear lube. I use this and change filters once a year no problems.

Great stuff, same as I use in mine!

Well, I don't see any M8 drive issues being discussed. Sounds good.

Interesting
So is it purely a performance change or are there failures with the M8's as the original poster questioned?

Merc recommends the MTF because it can absorb water well. The torco rep suggested I use the RTF for a more severe duty application. For us, the MTF would get extremely dirty, and the RTF was marginally better. Matt at TNT sets our drives up as well. We will be trying the Bravo Shop NEO oil this summer.

I would have to assume it is the performance and /or better selection of gear ratios in the #6.The M8 has a bigger gear set in the lower which makes the bullet bigger and requires bigger diameter props thus higher slip numbers.

That makes sense.......extra durability, but a speed surcharge.

I never had a drive problem with my 6's. Very minimal maintenece and lots of abuse! Now my engines on the other hand :rolleyes::rolleyes::rolleyes:

Back to the origanel ? here boys, The M8 I was talking about broke off gimble at yoke and was hanging by steering rams. Drive is one inch longer and bigger bullet creates massive stress on gimble ass'. #6 in my eyes is top notch quality. Why try to change it.

thanks all for the great response.

B38 :party-smiley-004:

Was it under warranty?

Yes . this unit broke in 15 minuets of hard running. Maybe just a flook. Once again, #6 is the stuff.
Maybe one or ten years from now I may own a 6.:lolhit:

Read this whole thread and not one picture, backup to the story, nothing... So what's the real agenda behind the post? All I have read was yes the #6 is a good drive, but we know this, and no one has heard of a #8 failure that's documented.. Sooo what's your point?

Oh good, at least it was covered by warranty. The 6 is a great proven drive. The M8 will ultimately prove itself to be superior from a durability standpoint.. Of this I have no doubt.