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Mercruiser 7.4 Replacement/Upgrade

Old 09-23-2021, 09:32 AM
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Default Mercruiser 7.4 Replacement/Upgrade

I have a 2001 Sea Ray 260 BR bowrider with a Mercruiser 7.4 MPI Bravo 3. I recently got stuck and was told the engine needs replacing.

I'm not sure what happened as I heard a clicking sound that got louder and louder and then the engine seized. No alarms. Mechanic said there was oil everywhere and engine can't be repaired.

It only had about 800 hours and no signs of any problems (compression test and oil analysis) I've only had it for 3 seasons. I'm going to get a second opinion on the engine but I was wondering what possible upgrade options I would have with a 7.4 with Bravo 3.

I've read good things about the 6.2. The new 8.2 looks like a great engine but says it's compatible with the Bravo 3 X so I'm not sure if that would require replacing the drive unless extra work can be done to compensate for that difference.

The boat is 27 ft and weighs 4450 dry. If the engine needs replacing I'd like to future proof my boat as much as possible.

Any ideas or suggestions would be appreciated and if you have a ballpark price.

Thanks

Scott
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Old 09-23-2021, 10:01 AM
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502 mag MPI would work, 415 hp stock should drop in with no mods
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Old 09-24-2021, 11:16 AM
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i'm in similar situation to you i have a 1999 sea ray 260 sundancer that i just repowered with a used 7.4l "performance tuned" carb motor. finally got numerous issues sorted out with the drive, bravoitis, bad carb, bad fuel pump, bad sea pump etc. seemed like she was running great. took her out and ran good for a few hours than on the way home something went boom. blew out the ceramic part of the spark plug. now have low compression on 3 cylinders so i'm not in as bad of shape as you seem to be. Trying to figure out best upgrades to make if this motor can be rebuilt is making my head spin.

As for your situatino, a lot of people go to the 6.2/383 stroker and are very happy with that as a replacement, it has similar power to what you had before and less weight and will give you more room in the engine bay too. Of course, they are not cheap. If you plan to keep this boat for the long haul and are happy with it, it's worth it. You could also definately consider stepping down a bit in power and going with a 5.7 but i know nobody wants to feel like they are going backwards but that should still be a solid power plant for that boat. Its hard to come by 7.4l blocks and when you do they aren't cheap but there shouldn't be any reason why you can't just get a rebuilt block from somewhere and swap all your parts over to it.

those BRAND SPANKING NEW 6.2s look sweet though. if money is no object that route gets you 3 year warranty on the motor and could be worth the spend.
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Old 09-24-2021, 12:09 PM
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if you replace a BB with a SB you are going to have exhaust alignment issues at the transom
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Old 09-24-2021, 12:17 PM
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Originally Posted by F-2 Speedy View Post
if you replace a BB with a SB you are going to have exhaust alignment issues at the transom
what if he adds in 3 inch risers? will that get his manifolds back up to similar position? people make swaps from sbc to bbc all the time so there has to be a way to do it right?
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Old 09-24-2021, 01:31 PM
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its not just the height its the width also............yes you can do it with custom exhaust tails

EDIT: if you go from a BBC 9.8 deck to a 10.2 BBC tall deck you have issues also
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Old 09-24-2021, 04:32 PM
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Add
HP is great but boat needs torque to get up, and your 7.4 has more low end torque then a 6.2
Would not recommend a new CAT 8.2, but get an older 8.2 is all good. Or rebuild your 7.4
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Old 09-24-2021, 08:33 PM
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Originally Posted by F-2 Speedy View Post
if you replace a BB with a SB you are going to have exhaust alignment issues at the transom
A 260 sea ray probably uses a MerCruiser y pipe and through the drive exhaust.
I have a few customers in similar situations right now. Merc doesn’t offer a drop in non catalyst complete big block right now that I can find.
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Old 09-25-2021, 02:21 AM
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383 Stroker MPI 6.3L Mercruiser is your go to small block engine for the older 7.4L engines.. 350 HP and 390 Ft lbs of torque @3800 rpm. And you'll have a 10%+ gas savings.

Go to Mercurymarine.com to find a dealer in your area that is a qualified re-power center.

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Old 09-25-2021, 06:11 AM
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Originally Posted by AmiableDave View Post
383 Stroker MPI 6.3L Mercruiser is your go to small block engine for the older 7.4L engines.. 350 HP and 390 Ft lbs of torque @3800 rpm. And you'll have a 10%+ gas savings.

Go to Mercurymarine.com to find a dealer in your area that is a qualified re-power center.
But...how much hassle involved? I've been considering a re-power myself for some time but essentially want a "plug and play", i.e. take out the old 454MPI and drop in the new more powerful engine, hook up exhaust with little or no mods, engine electrical with no mods, attach fuel line and go. A 502MPI or HP500EFI is what I've been looking at...just hard to find pre-owned...
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