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2000 454Mag MPI Offseason Refresh

Old 11-20-2020, 09:01 AM
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Default 2000 454Mag MPI Offseason Refresh

Hi all, long time follower of the site. Apologies in advance, this is a long read, grab your coffee first lol. We have a 2000 Powerquest 260 with 454Mag MPI. We have right around 600 scanned hours. We bought in Fall of 2019. Last off season, I did the following: clean flame arrestor, repair skeg, replace plugs, wires, cap and rotor, ignition module. Also replaced fuel injectors and the ECM re-flashed by Smitty to match the higher flow injectors. The boat runs great, we understand its far from a race boat and that's fine by us. We spend most of the time cruising (freshwater) right around 3000RPM, with an occasional blast to 3/4-full throttle - I baby her...As I was winterizing this year, I inspected the exhaust manifolds and they are pretty corroded internally and externally. They are 20 years old, so it's time to replace. We have the OEM Merc manifolds connected directly to the elbow (no risers). Elbows connect to 4" exhaust hose, hose connects to Corsa silenced tips. The hose is deformed internally and is time to replace. So, I want to replace the exhaust and hose and keep the tips. I would like to use aluminum exhaust to cut weight and *hopefully* have at least a little hp gain. I am considering the Imco Thumpers and EMI aluminum version as well. I see Hardin Marine has an entry level set as well. Does anyone have any recommendations? The motor is completely stock aside from the injectors and will stay that way, so I don't need anything exotic in terms of exhaust manifold. I also noted in the exhaust, the flappers in the tips have rubber that goes on the round part of the flappers and that rubber is shot. Can this rubber be replaced? Can I just remove it? I see there are replacement flappers as well. Trying to figure out what to do with these....


So, since I'll have the exhaust removed, what a good time to look at other items to be worked on.....So I'm thinking that I'd like to pull the heads and have those freshened. I'd love to replace them with aluminum, but that's just not in the budget. I figure at 20 years old, it would be good to replace the head and intake gaskets, check the valve springs, valve seats etc. I also thought I'd get a port and polish done while at the machine shop. Is there anything else I should look at while I have these off? This motor should have hydraulic lifters being a Gen6. Should these be inspected? Push rods? Rockers? Springs? Again, trying to keep this fairly economical so I can buy the sea deck for the cockpit the girlfriend really wants lol. However, if there are some smart upgrades that will ensure reliability, I want to look into that.


Also, I live in West Michigan, does anyone have any recommendations on a local machine shop that would do well with the head work? Thanks in advance and sorry for the long post!
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Old 11-20-2020, 09:11 AM
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Originally Posted by burtonrider11 View Post
Hi all, long time follower of the site. Apologies in advance, this is a long read, grab your coffee first lol. We have a 2000 Powerquest 260 with 454Mag MPI. We have right around 600 scanned hours. We bought in Fall of 2019. Last off season, I did the following: clean flame arrestor, repair skeg, replace plugs, wires, cap and rotor, ignition module. Also replaced fuel injectors and the ECM re-flashed by Smitty to match the higher flow injectors. The boat runs great, we understand its far from a race boat and that's fine by us. We spend most of the time cruising (freshwater) right around 3000RPM, with an occasional blast to 3/4-full throttle - I baby her...As I was winterizing this year, I inspected the exhaust manifolds and they are pretty corroded internally and externally. They are 20 years old, so it's time to replace. We have the OEM Merc manifolds connected directly to the elbow (no risers). Elbows connect to 4" exhaust hose, hose connects to Corsa silenced tips. The hose is deformed internally and is time to replace. So, I want to replace the exhaust and hose and keep the tips. I would like to use aluminum exhaust to cut weight and *hopefully* have at least a little hp gain. I am considering the Imco Thumpers and EMI aluminum version as well. I see Hardin Marine has an entry level set as well. Does anyone have any recommendations? The motor is completely stock aside from the injectors and will stay that way, so I don't need anything exotic in terms of exhaust manifold. I also noted in the exhaust, the flappers in the tips have rubber that goes on the round part of the flappers and that rubber is shot. Can this rubber be replaced? Can I just remove it? I see there are replacement flappers as well. Trying to figure out what to do with these....


So, since I'll have the exhaust removed, what a good time to look at other items to be worked on.....So I'm thinking that I'd like to pull the heads and have those freshened. I'd love to replace them with aluminum, but that's just not in the budget. I figure at 20 years old, it would be good to replace the head and intake gaskets, check the valve springs, valve seats etc. I also thought I'd get a port and polish done while at the machine shop. Is there anything else I should look at while I have these off? This motor should have hydraulic lifters being a Gen6. Should these be inspected? Push rods? Rockers? Springs? Again, trying to keep this fairly economical so I can buy the sea deck for the cockpit the girlfriend really wants lol. However, if there are some smart upgrades that will ensure reliability, I want to look into that.


Also, I live in West Michigan, does anyone have any recommendations on a local machine shop that would do well with the head work? Thanks in advance and sorry for the long post!
I have used Holland Automotive and Machine to refurbish multiple sets of heads for me with good luck and reasonable pricing. They have also done a few blocks for me.
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Old 11-20-2020, 09:20 AM
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How about the CMI Fusion Header? A little more expensive than manifolds but look amazing. I think it will line up to your exhaust tips as is.


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Old 11-20-2020, 09:25 AM
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Here’s what it will look like on your boat.


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Old 11-20-2020, 09:29 AM
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Dave at WESCO Racing is in Western Michigan. He’s a stand up guy that does good work. You can mill the heads to get higher compression ratio, get larger valves, more cam to go with your better exhaust system and you might be flirting w/ 500HP. The sound alone will be worth the investment.
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Old 11-20-2020, 10:53 AM
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The CMI's are sweet but more than double the price of the IMCO Thumpers, those just won't be in the budget. And as much as I'd love to play around and make some big numbers HP-wise, that's not the goal. I'm looking to gain a little extra, but I don't want to sacrifice reliability. If our boat had a hull that did well with more power, I'd go that route, but that's not the case

I appreciate the heads up on Wesco, that's like 15 minutes away from me. And I'll have to check out the place in Holland that was mentioned above as well.
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Old 11-20-2020, 12:12 PM
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Wesco
X2
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Old 11-20-2020, 02:38 PM
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Since you're running a single, you could also do Lightning headers. They are a little more but you can get them to fit your application and they do work great. Mine are 22 years old and still look good inside.
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Old 11-23-2020, 08:27 AM
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I have used both EMI and IMCO, both good products. You will not gain any speed by switching to these or CMI headers. It takes a lot of HP to gain 1 MPH. The boat is heavy and being a single engine enjoy what you have. Another good reasonable priced is Stainless Marine.
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Old 11-23-2020, 08:52 AM
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I have used EMI and they are great. I'd recommend the stainless risers as well
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