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TOPIC: 76 American jet

76 American jet 2 years 1 week ago #126763

Hi everyone, this is my first post in this forum. I wanted to show my project boat that I picked up last year. It is a 1976 American 18 foot. Berkeley jet, set up for 455 Olds. The previous owner blew the old engine and pulled it before I bought the boat, so it still needs another motor. I am replacing the transom wood and stringers, and then installing a rail mount system, so it might get a BBC next time around. If it turns out that the hull is light enough, I might go with a SBC instead.

The lines on this boat are so different from most of the 70's jet boats that you see running around with exposed engines and over transom headers (Tahiti, Kona, Specter, etc.), which makes it pretty unique. It needs a bit of work on the interior...new wood bases for the driver's seat and back bench seat, but otherwise it is in really decent condition. It might take me a while to get it all finished, but someday it will be on the water.
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Re:76 American jet 2 years 1 week ago #126766

  • 63 Sabre
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First let me say Welcome.
Second let me say WOW! That is a project that would be fun fun fun.
Nice lines. You got me snowballed with BBC - SBC ???
I've see several of the older jets with Ford 460's. Never had a jet to work on but it is on a bucket list.
Keep us informed.
Cal
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Re:76 American jet 2 years 1 week ago #126795

63 Sabre- BBC is a Big Block Chevy, usually a 454. SBC is a Small Block Chevy, usually a 350.

That looks like it will be a nice running hull. So many of the typical jet boat designs are more river, or flat water design. The deeper V in the bow should let her ride better in chop. I'm jealous of the windscreen.
Is there a big difference in weight between the BBC and SBC? If you aren't looking for the Big Block rumble, maybe a 350 with a Paxton blower can give you the same performance. If balanced, even raise your RPM significantly.

Will

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Re:76 American jet 2 years 1 week ago #126796

thanks for the welcome :)

@Sabre, like Willdiver said, BBC/SBC is either big block or small block chevy. There is a huge debate on whether or not a small block has enough torque to turn a jet pump at max efficiency, but it can be done if the hull is light enough and you have the right impeller. Personally, I'd prefer a sterndrive just because I have very little practical experience operating boats, and a jet can be tricky for beginners.

@Willdiver, I've seen some videos of a copy called an Apollo Starblaze on youtube, and it seems to run really nice, even in rougher water. You are right, even though it is a fairly low profile hull, it has a deeper v angle than most typical jet boats.

A mild 454 chevy (cam mainly) will have enough power and torque to run it up to about 55-60 mph tops, but it weighs more and will not be quite so nice on fuel. A slightly built 350 (cam, good heads) might also do well, but again, it depends on the weight of the hull, and the choice of impeller. SBC parts are definitely less expensive, but it might need more power goodies to do what the BBC can do with just a decent cam installed. The trick with either engine on a jet is not to get max RPM, but to hit a specific target RPM for max pump efficiency for a given impeller. As an example, with an A cut impeller, generally you want all of your power and torque in by about 5,000 rpm because that is where the jet pump works best. A 454 can do that with no more than about 330 hp. To get the same result with a 350, you'd need a C impeller, 6,000 rpm and closer to 400+ hp. The big block can do it with less mods, but those mods will cost more than the same mods to a 350.

As soon as i figure out how to post multiple photos, I'll set up a gallery so i can show my progress.

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Re:76 American jet 2 years 1 week ago #126797

  • 63 Sabre
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Multiple photos are done by editing your original post. Say you post 1 picture and want to place 4 underneath it. after you submit your first post click on the 'edit' button that is alongside the "reply" and add another photo and submit. you have to do this for each new photo but they will all be on the same post. Doing it that way allows you to comment above or below your photo.

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Re:76 American jet 2 years 1 week ago #126800

  • Kerry
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Does the Berkeley have a Jetovator? If it is, either engine would be ok. If not, remember the jet drive is set at the factory for trim with a specific weight balance, so going from a big block to a small block could bury the nose. Not sure, but I believe Berkeley had shims for the nozzle to slightly change the trim angle if necessary. Just something to consider.

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Re:76 American jet 2 years 1 week ago #126802

@Kerry, no, but I am looking into picking up a place diverter (same thing as a jetovtor). Yes, you can wedge out the nozzle on a berkeley pump, but it is still a fixed angle and is sort of a hit or miss kind of thing trying to figure out which one to get. A diverter is infinitely more adjustable and does a much better job of trimming out the boat at various speeds. Plus, you get the cool rooster tail with it :P

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Re:76 American jet 2 years 1 week ago #126803

  • Robby321
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Better of a BBC as jets like the torque..

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Re:76 American jet 2 years 1 week ago #126806

... and a big block just LOOKS better, c'mon! :P

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Re:76 American jet 2 years 6 days ago #126819

Hey Cal......

greenbay.craigslist.org/bpo/5752336966.html

Price is right, and right in town!!!! We can race Marlin's!! Maybe set up our own Green Bay Marlin club!

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Remember - There's always room for one more project!! (not really, my garage is full!!)

1963 Lone Star Triton w/ 1979 55 hp Johnson (soon 1963 Merc 850!!!)
1968 Lone Star Mustang w/1974 70 hp Evinrude
1974 Marlin with 1971 Merc 1350
1980 Glastron GT-150 w/1977 115 hp Johnson ( soon 1977 Merc...

Re:76 American jet 2 years 6 days ago #126829

Robby321 wrote:

Better of a BBC as jets like the torque..


+1^^^. Why do you think the original motor was a 455 Olds? Massive torque!! 'Twere me, I would consider a GM 502.
Larry

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Re:76 American jet 2 years 5 days ago #126856

  • Kerry
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No replacement for displacement- except MORE displacement!!! Want to dream or drool? Check this out!!!! hotrodenginetech.com/sonnys-1005ci-billet-v8-cranks-2150-hp/

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Re:76 American jet 2 years 5 days ago #126881

Bavk in that era, the 455 Olds was plentiful and cheap compared to the other makes. You will see a lot of jet boats from that era with the 455.

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Re:76 American jet 2 years 5 days ago #126885

mountainhawk wrote:

thanks for the welcome :)

@Sabre, like Willdiver said, BBC/SBC is either big block or small block chevy. There is a huge debate on whether or not a small block has enough torque to turn a jet pump at max efficiency, but it can be done if the hull is light enough and you have the right impeller. Personally, I'd prefer a sterndrive just because I have very little practical experience operating boats, and a jet can be tricky for beginners.

@Willdiver, I've seen some videos of a copy called an Apollo Starblaze on youtube, and it seems to run really nice, even in rougher water. You are right, even though it is a fairly low profile hull, it has a deeper v angle than most typical jet boats.

A mild 454 chevy (cam mainly) will have enough power and torque to run it up to about 55-60 mph tops, but it weighs more and will not be quite so nice on fuel. A slightly built 350 (cam, good heads) might also do well, but again, it depends on the weight of the hull, and the choice of impeller. SBC parts are definitely less expensive, but it might need more power goodies to do what the BBC can do with just a decent cam installed. The trick with either engine on a jet is not to get max RPM, but to hit a specific target RPM for max pump efficiency for a given impeller. As an example, with an A cut impeller, generally you want all of your power and torque in by about 5,000 rpm because that is where the jet pump works best. A 454 can do that with no more than about 330 hp. To get the same result with a 350, you'd need a C impeller, 6,000 rpm and closer to 400+ hp. The big block can do it with less mods, but those mods will cost more than the same mods to a 350.

As soon as i figure out how to post multiple photos, I'll set up a gallery so i can show my progress.


Looking forward to seeing more pics! You probably already know this but one advantage of a larger displacement engine is that it isn't working as hard to produce the same power as a smaller engine. Unlike a car engine, boat engines never get to throttle down, they are essentially climbing a hill the entire time they are running. An engine with more torque can operate at a lower rpm and will last longer...although as you pointed out it depends on the weight of the boat and the pitch of the impeller.

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20.5' 1966 ClipperCraft, 18' 1978 Olympic, and a 12' 1959 Elgin Car Top.

Re:76 American jet 1 year 11 months ago #127806

ok, I just loaded a bunch of pics into a gallery, but I have no idea how to link that with my profile. Anyway, here's the photos...

www.fiberglassics.com/gallery/category/648-1976-american-18-ft-part-1.html

Now that the weather is cooling off, I should be able to get a bit more work done before it snows on me. I need to finish cutting out the old glass from the edges of the transom, remove the jet pump intake, grind the rest of the wood down to the fiberglass, cut out the stringers, make templates for replacements, then put everything back together. THEN I can start hunting for a motor and maybe get this thing on the water before the next decade arrives.

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Re:76 American jet 1 year 10 months ago #128806

well, i'm getting ready to remove the jet intake from the hull so i can finish removing the old transom and get to work on replacing that bit. The plan is to remove the bolts, put a floor jack under the intake (with a block of wood of course), put a bit of pressure on it, then hit the epoxy with a heat gun. Then hopefully, I'll hear a nice little POP and have the intake out of the way.

One tricky part...I'll also need to replace the stringers, and I was told to not do that while the boat was on it's trailer. I understand the reason behind it, but in my case, I don't have any flat ground to block up the hull. Plus, this boat is sitting on a roller trailer which should self-adjust to keep the hull un-flexed. I know it's not ideal, but it's what i have to work with. The stringers are also 1/4 length so it's not as critical as with full stringers.

This is what it all looks like right now...(by the way, I've loaded a bunch of photos into my gallery, the link is in my previous post)
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76 American jet 1 year 4 months ago #131527

Now that is has mostly stopped raining every other week, I'm back working on getting the jet intake out of the bottom of the hull. Wishing I had an air chisel to break the old epoxy from around the intake, but I'll have to do it by hand. Once that's out, I can finish prepping the fiberglass for the new transom.

It also looks like I'll get to do the stringers, but it might be possible to only replace part of them. Has anyone here done a partial stringer replacement? The stringers are the 1/4 variety and the rot might only be in the last 12 inches or so, so I'm not sure I'd need to replace the entire thing. Any thoughts?

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76 American jet 1 year 4 months ago #131528

  • 63 Sabre
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One of the tools I found almost indispensable when working on the old girls is a cheap Harbor Freight oscillating saw. You can cut right through the old resin and glass and wood and bolts etc. Go on line and get some of those % off coupons and you can probably pick one up for around $30.
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76 American jet 1 year 3 months ago #132102

That's the exact kind of tool that I've been using to cut the old glass from the transom, also started cutting the back half of the stringers with it. I've also been using it to cut the resin/epoxy (not sure which one it is) from around the pump intake.

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76 American jet 1 year 2 months ago #132596

Hey Mountainhawk, that looks awesome and well-built. I even like the choice of color.

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76 American jet 1 year 1 month ago #132997

Thanks. I'm very happy with the look of the boat. The color was a repaint by the previous owner...not perfect but it looks from from 10 feet away.

Right now I have a bit of a dilemma....which engine to use. The boat is a jet, originally with a 455 Olds (NOT an engine that i plan to replace). My other options are go with the traditional 454 big block, or use a smaller 350. Right now, i actually have an OMC 260 (marine 350 Chevy) in another boat that i can use. A cam change, aluminum intake manifold, and I might be able to get 290+ hp out of it. That, plus swapping to a B impeller, and it should work fine. Or, I can hunt all over the place for a decent running 454. Here is the pros/cons for each...

350 pros...
lighter weight
better fuel economy (maybe)
cheaper parts
I already own it, which means less $$$ to spend.

350 cons...
lower baseline hp and torque than a big block, which means it might not be quite enough to run the jet without putting money into it.

454 pros...
higher baseline hp and torque, better for jet
more "out of the box" power potential than a small block

454 cons...
heavier
worse gas use (maybe)
would need to find and buy
would probably end up with a peanut-port truck motor

So, the "better" engine (big block) will definitely cost me more money right form the beginning, and spare money is something I don't have much of right now. On the other hand, I don't plan to race the boat and I'd be happy with 55-60 mph out of it. The question is can I get that with the small block?

Most jet boaters that i know say "get a big block, cause there's no replacement for displacement"...true enough, but I have also read about plenty of well running jets with mild small blocks. Any thoughts???

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76 American jet 1 year 1 month ago #133079

  • 63g3
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Hi,
So I have a jet, a Keaton Boats J18. I'm in Massachusetts but had to go to CA to get one. It has a small block, a Chevy vortex 350 (Indmar) which puts it a tick over 320 h.p. . Its 18 feet very similar to yours but it has a different model jet where intake is partially molded in the area where the hull and transom meet. This saves room in the boat as engine can move back it also puts the weight more rearward which helps top speed some. It runs 67 and will throw your back out on accel. This is very comparable to the performance when the Keaton's were built with 455's and 460's. So today's small blocks compare very well to yesterday's big blocks.
For an excellent comparison go to the Keaton Boats club website, Powerboat magazine did a comparison of a 460 ford vs a small block in the early 80's. Even the performance guys at the test said they would most likely opt for the 350 where there was minimal Perf loss and significant gain in economy not to mention the lighter weight helping handling. Keep in mind today's 350's compare even better. Spend your money an a good set of heads, that's why the votex motors are so much better. Lots to pick from for your earlier 350.
My pump is an American Turbine but it's reall a Berkeley at heart, they bought all the tooling. They are still making pumps and have parts for everything, go to their site and surf around as it's very informative. They have the pump curves for each impeller. They are located in Washington state.
This is my first jet...always wanted one.... and I too, like a decked over motor. I did a lot of research and asked around (Scream and Fly)
I have a few fast outboards so I frequent that site. .....asking the same question you are.
Driving a jet is like driving a car with a loose converter if you have ever had a car built with one.
The pumps don't gain efficiency till around 3000 plus rpm so, lots of rpm with not much action below that and start loosing again after about 4600 so, you just throw hp away if spinning above that. That is pretty much regardless of impeller size and assuming it's just a stock jet pump. Jets are ridiculous out of the hole (very quick) because the motor can spin right up to the fat part of the torque curve. An A impeller is where you want to be a B is most likely to big for the hp you are circling with 300 hp in that size boat.
Big blocks were used for a few reasons, some emotional some practical. The more hp you develop at or below 4600 the faster the boat will be as you can move up impeller size as hp increases, big blocks as a general statement can generate more hp at that rpm than a small block so potentially they could be faster. ...just a simple displacement thing. Torque is really what accelerates the boat so a slight edge to big blocks somewhat mitigated because you are accelerating a lot more weight. So all things being equal back in the day there was more potential performance modifying a stock big block rather than a small block as the starting point and stay within the upper rpm limit.
The 455 Olds and 460 fords are common as that's what Berkeley bundled the jets with, Olds from what I understand were priced better than other big blocks so that's why they were used.
Given the similarities of our boats I'd give a 350 with good heads and a cam for power at 4500 the nod over a big block. There is real comparisons and experience backing it up. That said a big block obviously will work too.
Good luck I love the look of your jet.
Randy
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