Offshoreonly.com - Turning my Merc 850's into 1075's... Any Thoughts??

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Quote:

Originally Posted by maxonmike (Post 3585913)

I own a 36 Nortech Cat with Merc 850's and they have about 190 hours on them. I think its getting time to show them some love and do a full rebuild. I can bump the HP up to 1075 with minimal extra expense on the rebuild. I know that 1075's operate in a higher RPM range and I realize the next rebuild time will be shorter however I got that need for speed.... Any thoughts???

Be very selective in choosing who does your work.

Quote:

Originally Posted by A.O. Razor (Post 3585927)

Personally, I would not think so much about the resale. They are discontinued motors with a solid roller setup. Also, the 850 is from what I understand, not the most popular of the bunch. Young Performance and others have had good succes with upgrading them with hydraulic roller setup, and that will give you a more reliable setup with longer times between rebuilds, the future rebuild will most likely be cheaper too. If going for 1075 hp, have in mind in what way. Merc, Ilmor, Volvo ect. rates their motors by the SAE J1349 International Standard correction, and most custom builders rate their motors by the old and somewhat generous SAE J607 Land and Sea Standerd. This basically tanslate to a roughly 5% difference in power. So if you want 1075 hp compareble to your current 850 hp, make sure it's done by the SAE J1349 International Standard correction or use the SAE J607 Land and Sea Standard correction and make 1129 hp. 1129 hp SAE J607 would be comparable to the SAE J1349 1075 ho.

Good luck with it.

Apples to apples.

Very nice post I like it:drink:

Dyno first then change worth the coin. (use same Dyno)
:ernaehrung004:
We Dynoed some 1075 mercs and made 1088 how about that
SAE J1349 :drink:
Its all in the dyno maint we had some dyno sheets of a Superflow 901 that showed 15% correction, when asked when it was calibrated the employee didn't know! Dont worry they closed 2007.
Just My 2 worth - only .002 in today's market

I got tired of the 15 hour valve lash and oil changes so I researched it and was told that going to hydraulic roller was not the best combination for reliability when running 1075hp with mercs cam, setup, etc...
If merc did not do this, then I feel that they also researched it.
Other builders may, but then again their combinations are different. Merc's combinations seem to be the benchmark on reliability.

Mark Boos at Precision Marine did mine last winter. Big difference in performance. I had issues with idler pulleys and tesioners that were not replaced at rebuild, all sorted out now. Guardian mode that Sydwaz refered to was due to a neutral switch on the trans. Engine thought it was over revving. I did go to the new Whipple tensioner and idler pulley plate, nice piece. I also made new idler pulleys with 3 bearings for the ones behind the water pump. The pulley system had been my weakest link.

Mark is also seeing higher reliability with a new lifter he has been using. I shipped him the engines and then towed the boat down and he reinstalled them after rebuilds. If you are doing a complete rebuild, for the extra cost of blower pulleys and ECM reprogram it's hard to beat. I also highly recommend Mark:ernaehrung004:

Here's a link to the Dyno run...
http://www.youtube.com/watch?v=l2wgqt_fFps

Quote:

Originally Posted by wgg (Post 3586030)

Makes total sense to do at this time and costs would be close. Might consider buying another set of PCMs and running duel fuel.What kind of speeds are you getting now Good luck

We see speeds consistently in the high 120's to mid 130's on a good day... I must admit that I need to fly the boat a bit to see the 130+ speeds. Those with Cats know what I am referring to... Trim the boat a little more then you would normally to get the nose light... It does not bother me however sometimes it makes my passengers kinda uncomfortable. I think with the bigger power the boat will actually be more stable as I will not need to drive the boat as loose to get the same speed...

Quote:

Originally Posted by BraceYourself (Post 3586284)

Not sure I agree with you for a few reasons. If doing a complete rebuild and changing to hyd. roller, you will obviously use a custom grind cam and valve train spec'd for hydraulic roller setup. You don't need to spin super high rpms to make 1075 hp. Another reason is. As thing are today, well Merc racing does research things, but to bennefit who? Themselves with the insanely expensive rebuild or the customer that will pay for the rebuild? The good builders today, build 1200-1400 hp motors with better reliabillity than the Merc sc platforms. The only place I see them being the benchmark, is in the DOCH TT area. Their service and warranty sucks as well.

Not trying to turn this into a Merc vs. ??? It's just how I see it and it's subjetive personal opinion. I'd rather own Ilmor, YPM, Sterling ect. anything but Merc these days and I belive they can be turned into much better motors.

I agree Mark would be the guy to have do them however I'll bet he is slammed right now Never could understand why he spends money advertising Always busy, very loyal customers Great looking boat Btw

Don't know Mark, but Ron Potter would be an excellent choice for upgrades in my opinion. Good luck Mike.

Would you have to change props with the extra hp?

Quote:

Originally Posted by wananewboat (Post 3586505)

Would you have to change props with the extra hp?

Something I have thought about.... I am sure I will need new Props.... Right Now I have 17 x 36 and with the extra HP I do not think that will be enough....