Performance mod recommendations 175 EFI

I have a 2000 Mercury 175 EFI (OT151395). I owned it from 2000-2016 and I sold it. Guy who bought it blew it up and had a hole in the block. He had a local Merc Tech install a new BB block powerhead and it has the older style heads. Anyway, I bought the boat back. It runs great, but its just not as strong as the other motor that was on it. I could turn my Boger 25 Tempest to 5950 and run 65-66 with my partner and I. New one will only get to about 5600 and struggles to hit 60. Throttle plates are opening all the way, it just doesn't seem as strong.

Well this winter, I am going to pull the power head and replace the swivel pin and bushings and motor mounts, mainly because its 22 years old and I want piece of mind. I acquired a 200HP ECU that I want to try on there and while I have the powerhead off, what do you recommend doing to the midsection/exhaust plate/etc to go along with the 200 ECU? Im also going to put CCM reeds and maybe stuffers if I have the room. Can I swap to the 200 exhaust plate or is it the same as the 175?

I just want to help it breath better to go along with the slightly richer fuel curve and get the most potential out of it. Oil injection has already been removed

exhaust outlet on the block is a choke point,and the adapter plate and exhast plate. helping it breath in a little better will help a little. might be to rich with the 200 comp. the block is your restriction. find an ff to build

Changing the tuner is going to kill the bottom end on that 150... it needs the extra backpressure for the bottom end torque.

As suggested, it's the block itself that has the biggest restriction. Best things you can do are to cut the heads to optimize compression, fiber reeds (TDR is a good choice), and depending on whether it's got the CDM or ADI ignition setup- there may be some items there as well.

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Originally Posted by EuropeanAM

Changing the tuner is going to kill the bottom end on that 150... it needs the extra backpressure for the bottom end torque.

As suggested, it's the block itself that has the biggest restriction. Best things you can do are to cut the heads to optimize compression, fiber reeds (TDR is a good choice), and depending on whether it's got the CDM or ADI ignition setup- there may be some items there as well.

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Thanks Don, did you see that it is a 175 efi? It does have the CDM ignition. What are the options with that setup? Is Jay Smith still the best guy to send the heads to?

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Originally Posted by bob p

exhaust outlet on the block is a choke point,and the adapter plate and exhast plate. helping it breath in a little better will help a little. might be to rich with the 200 comp. the block is your restriction. find an ff to build

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The FF are hard to find. I have a longtime Mercury Racing engine builder that lives close to me. Would it be worth having him open those ports up a little and clean them up?

Thanks for catching that- but the 175 tuner is still considerably longer than the 200 tuner.

Otherwise, same rules apply (it's just a bit larger ports).

Your BB block is actually a 150 HP,if I remember correctly...Pretty sure.A 175 would be a CC block.The ports are smaller in the BB,Chris