merc notched exhaust ports

[mercrazy]

what year or what serial number did they start putting the notches in the 2.5-200hp exhaust ports?

[Talon2.5]

the one i have is a 90 or 91 block with the notches thats as far as my knowledge of the years goes on that:(

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[us1]

Are you sure that’s a 200 skip? I was my understanding that the 150s and 175s all had it and only the late 90s 200 have it. I would love to know the exact years on this because the 200 without the notch are what I use for my race motors and I’m not sure either on the exact year they started.

[Talon2.5]

i'll have to double check the year stamped in the block, but when i bought it there was another 2.5 there and it waqs the 175 horse and the exhaust ports were much smaller, this block was run on an allison that spun it 8000 rpm is the only background i have on it


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[Rusrog]

I have a 2.5 200 carb motor, 91 model with 2 bolt mains and has no exhaust port notches. I don't have anything to add other than that....

I can get the numbers off of the block if it helps you guys figure out what you want to know.

[us1]

Hey Russ, I have a 91 too with no notches and I have 99 and 00 with notches. I would love to know what year they started that with the 200. It would make it a lot easier buying motors I can see up front.

[Rusrog]

Hmmmm. That makes about as much sense as a football bat. I wonder what Mercury uses as a criteria for putting the notches in one??? I mean, there is no ryhme or reason that has corelation to the year, or horsepower or anything thing that I can see.
It's like they did it with a coin toss or something....
Has anyone really noticed a difference in starting or performance from a 'notched' motor to a 'non-notched' motor?? I guess I can see them doing it on some motors to lower the compression but does it really lower it that much and wouldn't it be easier to just take out a couple degrees of timing or something??

Just thinking out loud....:confused:

[us1]

They claim it makes it start better. All I know is if you are trying to make some power they have to go.

[stan merck]

i just worked on a 2001 and it didnt have them. i also have checked a 92 eng and it didnt have them. i also have checked a 96 eng and it didnt have them either. i thought only the 175 and 150's had the notches, i know i have checked some other year 200's and have never seen one with the notches, i am pretty sure one that i checked was a 99 too.

[us1]

Maybe these motors I have are 175s, not sure. Didn’t take them apart yet. I heard before that no 200 have it, but then these motors were said to be 200s so I'm not sure?

[stan merck]

I'll keep checking whenever we get a 200 in. since were on this subject on a very mild eng does the notch hurt you that much, I mean cutting the heads is going to raise the comp. I can see in your case you dont want it for sure. But all i got is a 175 block to work with.

[us1]

Yes, you can make some ok power with the slot still in. It just won't go all the way. I just resleeve them and then they are awesome.