CMI vs Gill
 

I am planning on upgrading my power and am wondering for a stock merc 500hp the HP diff you will see with cmi vs gill
didnt the 500hp come strock with gills?

Klaw,

The HP 500 carbed use the Gills. The HP 500 EFIs uses CMI. Same HP rating for both even though I have been told the EFIs will dyno with more HP than the carbed. The EFIs also use a different cam grind which is a little more aggressive than the cam used in the carbed version.

Hope this helps.

Be safe,
Mark

The motors I am looking at are carbed with 200 hours on them
I guess the biggest diff is the look factor of o tube exhaust manifod versus teh gil type thanks alot guys

Klaw, Go with the CMI's they sound better and look better.
Just my .02

Mark

Yes, the Merc HP500 came with the GIL exhausts, and the CMI's will give you maybe about 20hp over the GIL's. You may not feel it that much in the boat---maybe a little bit of a kick.

I jsust need to find a couple of used sets the motors are taking most of the budget along with the new interior

Try looking at this chart. HP between them all is close but the tube headers (CMIs) and the Eickerts seem to provide substantially more torque than the manifold styles.
http://www.arizonahotboats.com/exhaustdyno.xls

Go with the CMI's. You will thank yoursefl the next time you change spark lpugs.

Team Gary, That is definately a FOR SURE! It's like you need another thumb where your hand and wrist are joined together! Either that or you need to cut all your fingers off except for your index finger and thumb!

Canada Jeff, how is exceleration let's say from 3000rpm to WOT between you and your friend's boat?

Cmi's look alot better but the gill's last alot longer. From what I hear Cmi has a tendancy to crack and cmi is a little funny with thier warrenty.

I have CMI`s on my Top Gun and I am very happy with them, also have several friends with CMI`s and they are also pleased with thier product also.

I have owned several sets of Gils and have to say that I will never own them again. I have had problems with them and lost a motor once because of an internal leak. They are coated internally and externally with what they call "Gilcoat" It looks to me like some type of powdercoat process. After a season or so this stuff flakes off and looks horrible and in the waterjacket it peels off and clogs the water flow big time. I guess they were fine in thier day but with the price of CMI`s now about the same as Gils why would you want them.

Just my personal experience:crazy:

Klaw, A very reliable and very well known engine builder here on Long Island helped me make up my mind. He has seen the problem with CMI's cracking within a short period of time. CMI's warranty comes back with a "sorry, salt water thing" and your S.O.Luck. The only time he uses CMI is for higher H.P. engines. I was really disappointed because I was looking foward to using CMI's but really can't afford the big bucks every couple of years. The gil's I have are 10 years old and am in the process of shipping the entire system for a pressure test at gil's plant just as a precaution.

KLAW
The CMI's are a real nice product, they look nice and give you some additional hp, but they do seem to crack after two or three seasons.
The cracks seem of show up in the exhaust pipe, and not the maniflold. I'm convinced they crack from movement, combined with expansion and contraction.
Talk to CMI I have heard they have made some changes to the geometry where the pipe meets the exhaust manifold.
The ones that I have worked on have a tapered clamp and a fiberglass rope gasket , I do not know the technical term for the connection.
Good Luck Post what you decide to do.
Brian