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

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???

A buddy here in VA did that on his MTI. I know he is happy with the final results, but he had several gremlins to iron out--sensors, Guardian mode, tuning, blower belt ejections; nothing overly serious but frustrating none the less.

I wouldnt trade the Expense, the reliability nor the decreased resale value of that idea for the few minutes each season that you use the speed difference between the two packages.

One thing about stock Mercury products....for the most part you turn the key and go boating.
Turning the key and not having the engine running right is my single biggest pizz off in boating.
Wouldnt risk it.

Just my .02

Good luck with whatever you decide to do.

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.

Check with a couple of the builders, some of them have changed them to hydraulic rollers and have kept the power and upped the reliability. Bob Madera would be a good one to call and ask.

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

Agreed.

Check with Teague Marine , he just announced a program for that exact same upgrade you are talking about .

There is a guy here that did the same and they have ran great... Probably put 90 hours on the upgrade with no problems other than one bad sensor!

Bought a 850 boat that would run 115 to 118 changed it over to a 1075 all mercury parts ECM, Cam, Pulleys. Wouldn't go back we ran 135 at the end of the year.