I have a 99 500hp carb engine and would like to convert it to EFI with better aluminum heads and a cam change. Is it possible to use a 2003 525 intake, ecm, coils, ect to convert my engine? Is this ECM reprogamable and will it work with my analog gauges? Would it be better to use a 500 EFI intake and ECM?

Would the EFI convert be worth it or should I stay with a carb?

Thanks in advance.

I think you would find a 500EFI conversion way, way, easier....from what I've heard the 525's a a real bear to mess with. Not to mention closed cooling on them.

the 500efi would be the way to go, Arizona speed and marine makes most of the parts for the update, also look into the mono blade throttle body and ecm reprogram with the cam and heads will give you a big increase in power

are all 525 closed cooling

All the EFI 525 are close cooled, the older 525 sc were not. Steve

Thanks for all the info. I kind of figured the 525 would be a headache. The 500 EFI conversion sounds like a better way to go. My last two boats were injected and I liked it other than doing any modifications. A carb would make modifications easier but it has been so long since I have had a carb engine I am not sure I will like it. I will be making the transaction on the new boat soon and will run it as is for awhile, then decide if EFI is what I want to do.
Thanks,

you don't have to have closed cooling for the 525 systems to work. and if you put the crane 741 cam with aluminum heads everything would be the same as a 525 just no closed cooling.

Contact Tyler Crockett , he just did a bunch of r/d work on what you're looking for. 810-531-1809

Are you located in Spokane, Wa. If so check out the Seattle boat show and look up www.mercermarine.com (high performance) they seem extremely knowledgable with merc racing product and more. Looks like they even had some heads and intakes at the show to choose from.. Thanks, Cam-shaft.

Keep the iron heads you have and send them to Jim Valako -
He has some trick mods and will have you cranking out more power than a Merc 525 .
He is in Grand Rapids, Mi. -