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Pursuit Denali 2460 8.1L...should I stay big block?

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Pursuit Denali 2460 8.1L...should I stay big block?

Old 06-12-2019, 07:23 AM
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Default Pursuit Denali 2460 8.1L...should I stay big block?

Hello,

I bought a 1997 Pursuit Denali with a 8.1L with unknown engine problems. The unknowns are proving to be not a huge deal but now that we have half the engine out we have a few decisions to make. The 8.1L is an expensive engine for parts or a rebuild but I got an old school engine buddy on the project.

He's suggested just slapping a 5.7 in for a fraction of the cost of the 8.1 but I've had a few other buddies say the 5,000 lb boat with 4-5 people in 2-3ft waves on lake erie will be over taxed. I also see that 90% of these boats seemed to run the 5.7L. Of course another option would be a far cheaper 454ci.

I'm torn from wanting the fuel injection and slight economy with the big power when needed (and not having to re-pro expensive duo props) and going to a simpler (carb'd) and cheaper engine to maintenance in the long run.

Any useful comments are appreciated!
Old 06-12-2019, 07:33 AM
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Your buddy is correct. 454 will not be as fast as you are now bit far better than a small block requiring all the marine parts to change.

The make a 383 stroker than would have maybe enough power but frankly I'd stay big block.

Back up one step. What exactly is wrong with the current engine? Finding that answer is step 1. Anything external to the engine itself will just transfer to any other engine. If the engine turns over and has good compression you can completely replace ignition and carb systems for way less than a motor change.
Old 06-12-2019, 08:10 AM
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8.1 or stay home. They are tanks. I say fix it.
Old 06-12-2019, 10:32 AM
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Perhaps consider a Crusader 6.0 L MPI at 370 hp? ( No distributor)
https://www.1800runsnew.com/crusader-engines/

But apparently Michiganmotorz still sells 8.1 L I/Bs. However, there have been so many water ingestion problems with the 8.1s I would avoid them.
Old 06-12-2019, 10:48 AM
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Originally Posted by TTaxi View Post
Perhaps consider a Crusader 6.0 L MPI at 370 hp? ( No distributor)
https://www.1800runsnew.com/crusader-engines/

But apparently Michiganmotorz still sells 8.1 L I/Bs. However, there have been so many water ingestion problems with the 8.1s I would avoid them.
The 8.1 is the same block as a 454, correct? Water ingestion would be from backing up at high speed or chopping the throttle and getting slapped with backwash. Flaps on the exhaust should stop both of these. Is it a poorly designed exhaust? Doesn't that same exhaust get used on the 454?
Old 06-12-2019, 11:05 AM
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Originally Posted by Jumpsummo View Post
The 8.1 is the same block as a 454, correct? Water ingestion would be from backing up at high speed or chopping the throttle and getting slapped with backwash. Flaps on the exhaust should stop both of these. Is it a poorly designed exhaust? Doesn't that same exhaust get used on the 454?
Neither of those things cause the water ingestion problem in the 8.1's. The problem started occurring with a new cam grind to suite the new fuel injection systems. Water droplets are sucked back up the exhaust stream during low speed engine operation because of camshaft overlap issues. Most times, the water that is drawn in, causes the valve stems to seize in the guides. The results can be mild to catastrophic. Failures are most prevalent in salt water. Fresh water boats have a better track record with this. There is a shutdown procedure that helps prevent this. Running the engine for several minutes at 1500 rpm's before shutdown seems to dry things out in the combustion chamber and lessen these reversion issues.

I would get the 8.1 fixed. That boat is heavy and needs the torque that a 496 provides. If you are in a lake and follow the shutdown procedure, you will enjoy a good long engine life.
Old 06-12-2019, 03:39 PM
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Thanks. I accept your explaination but that's a long way to draw water. Even from a proper elbow. Has to be serious fault in the exhaust design. Steam might come that far back at shutdown if water were pooling somewhere in a hot area is all I can figure.
Old 06-12-2019, 04:01 PM
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I went from a 7.4Gi (310 hp) to a 5.7GXi (320 hp). The 7.4 broke hard at about 1500 hours. I never tore into it to find the cause.
I had 2300 hours on the 5.7 when I sold it. I never missed that 7.4 for a second.
The 5.7 is lighter. Provides more maintenance room in the engine area. Better on gas. Less torque and wear on the outdrive. Not long after the engine swap, I needed a new outdrive due to pitted gear sets.
I don't think giving up FI for carbs is what I would do. Achieving similar hp with a small block and saving 400 pounds is the way to go.
Old 06-12-2019, 04:11 PM
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The 383 Stroker is a great option at 350 hp and a big flat torque curve. It’ll turn more rpms to achieve the same speeds but with much less fuel burn. Weight savings and extra space are a bonus. MPI all day, it’s a very reliable system and going to a carb will be a big step backwards.
Old 06-12-2019, 04:32 PM
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Big blocks are rare in the 2460, as you said most came with a 5.7. If the 8.1 is not an easy fix I’d ditch it an throw in a new 6.0 or 6.2. Pretty sure they can be had up to about 420hp which would be plenty for that boat. Did you get this boat in Wareham by chance?
Old 08-06-2019, 09:28 PM
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Just a follow up...

Mechanic buddy has the engine apart and it looks great inside other then needing refreshed with pistons, rings, bearings, chain, oil pump, ect...

But running into issues finding (online) kids for an 8.1L in the 1997 range. We cannot find any identifications on the engine to confirm the size, model, build, ect...nothing. Being a 1997 (boat) it's a charcoal (joint venture OMC) Volvo Penta engine. I was told it's a 8.1L but it seems EVERYTING online with a 8.1L starts about 2000...so scratching my head. NADA lists a 8.1L option (no 7.4L) but GM marketing info makes it sound like that engine never hit the market for trucks until 99-00.

Can anyone shed light that I would have an 8.1L engine and how to determine engine specifics in a world that only seems to acknowledge 8.1L from 99-00+.

I've attached a document on determining the engine but we have no labels. It makes mention of head casting which we didn't see but will dive back into this weekend.
Old 08-07-2019, 03:23 AM
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I’m not sure about the marine market but the 8.1 was introduced in 2000 for the model year 2001 trucks. I’d give Pursuit a call to confirm but I believe that boat came with a 5.7 or 7.4. If there’s no markings on the engine what makes you think it’s an 8.1?

BTW I owned a 2000 2460 with a 5.7 and never once thought it was underpowered.
Old 08-07-2019, 04:50 AM
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I bought a 2001 2860 last year (debated going for the 2460....) and mine has the a 7.4l gi (fuel injected). Something doesn’t make sense regarding the size of the engine. The PO of mine saved most of the info including the 2001 pursuit catalog which lists the power options.



Doesn’t seem possible that you could have an 8.1 in that boat.
Old 08-07-2019, 04:55 AM
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If its an 8.1 new style, then it is nothing like a big block, it is its own beast. Think of it as the LS1 of big blocks. Is it a old school 496 which can be a classic BBC block. Have to get the block casting number. Grab a smart phone, turn on the flash, and start taking pics to find it. Model number should be on the top somewhere too usually the ecm.
Old 08-07-2019, 06:09 AM
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Measure the bore and stroke.
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Old 08-07-2019, 07:33 AM
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There have to be casting numbers. Also stroke is different than 454.

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