Is it too late to in on this one?

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Heres our mini

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Love seeing this old thread resurfaced. Here’s mine. She’s a ‘78 and has what appears to be a pretty much stock 460.


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Very nice!!  I'm going Mild 6.0L LS just to get it in the water. After a little time I'll likely add a procharger. I'm already rebuilding the berkeley and having a new impeller cut to match the LS.  I know once I go procharged I'll have to dump more $ in the pump. For now it should be fine for the family.  Hopefully I'll see you guys out there next season.

What are you having the impeller cut to?  That boat is not going to like anything much smaller than an A cut out of the hole.

So, the engine is supposed to Dyno around 450HP.  It's not done yet, but based on the build, it should be pretty close.  I built another engine like it a while back with the same components and it came in right there.  I've talked to 3 different Jet shops and all of them said "B/C or B+".  I'm also going to ditch the original rear transom cover and go with the customer setup to make getting the bowl off faster so if the cut is wrong, it won't be a pain to switch to another impeller.  I'm not trying to build a rocket since it's a Mini day and decently heavy.  I'm looking more for a family cruiser.  If it's not fast enough or struggles, I'll add the pro-charger.   

I don't mean any disrespect, its your money and your boat.  However, I don't see any mention of RPM.  I also have to ask, are the three shops that recommended a BC and a B+ impeller aware of exactly what hull you have, or are they assuming a lightweight bubble deck?

As you mentioned, you have a heavy hull.  A larger boat neads a larger impeller to help get it out of the hole.  Once you start adding horsepower, the problem gets worse, you will run into problems blowing the pump dry.  I think you will be happier with a larger cut impeller to increase out-of-the-hole response and better fuel economy.

On a side note, if you have the option of an aluminum block, that would make a great lightweight running package.

Just running some numbers, a BC impeller is going to absorb 450 horsepower between 5400-5500 RPM.  A B+ impeller will absorb 450 horsepower between 5100-5200 RPM.  A 30-degree A cut, or "small A" impeller would be at 5000 RPM.  In contrast, a C cut impeller would absorb 450 horsepower at 5600 RPM.  I would strongly recommend against going that small.

If you are making your 450 horsepower at a higher RPM, the impeller will never allow the engine to turn that RPM.  It's all about WHERE you are making the power.

All I am saying is, try the impeller you have BEFORE you cut it down.

The ProCharger is a good call if you decide to go forced induction.  I think a centrifugal is best suited to a jet boat.  Compared to a positive displacement blower, a centrifugal blower comes on when you want it (upper RPM).

I have the 20.5' posted a few pages back.  It had an MPD fully detailed B+ impeller when I got it.  The B+ allowed the engine to RPM way up where it wanted, but I had to backpedal a lot to get it there.  I definitely didn't get the "shot out of a cannon" feeling until I put in the AA.  The AA hooks right now and cruises at 50 MPH at about 4000 RPM.

I want to play too.  My '91 20.5' 454/Berkeley JG-AA.  I don't have any recent pictures on the water as it has been on hold for some family matters, but now making progress.  Once I get a computer online, I will post a build thread.  Shooting for TPM

Flusher, it's all good! I know you know what your talking about! So again it's a 6.0L iron block LS With aluminum heads. The build should make 450ish peak HP at 5800. That's what the last one I built did. All three shops I talked to know my hull. In fact one of them just did the exact same LS setup for a customer with my exact 18.5ft Hallet Mini.  Customer said it was perfect and brought it in with an A cut.  I guess I really won't know until it's all together and it's in the water. It's a tough call because the jet needs a rebuild and everyone is saying B/C or B+. I'd like it to be right on the first shot. But I understand it doesn't always work out that way.  Also, I'm planning pro-charger only because I'm trying to keep everything within an enclosed engine compartment and yes, I prefer the power up top.

Why do they recommend a BC or a B+?  Why not a B and split the difference?

Why do you "prefer the power up top?"

Just trying to inspire thought on the topic.

Honestly, I was expecting a 19' or 20', not an 18.5'.  It makes a difference, especially after powerlifting my bare hull around last weekend.  I can lift a 19' bubble deck and place wood between the hull and trailer bunks by myself.