Pondering a new engine build for the jet boat

Been going back and forth about what to build engine wise for the jet boat this year. Currently it is a 466" with a weiand tunnel ram, two 750s, iron cj's, logs and the wrong cam. I have debated doing a 557 with the same top end and a custom solid flat cam. Keep the logs (hardin long bolts)
I have considered a 532 with scjs and sell the iron heads.
I am also considering a forged 500" with twin turbos through the logs. That eliminates the scavenging problem. I can fab everything and do a ms3 myself but it is really more than the jet can handle so it opens a can of worms..
I have been looking for a used set of water jacketed cmi or lightning bbc headers for a while to help but the question is, what combo would you do and is it possible through cam timing changes to make decent power through the logs with a big inch combo?

6t6mustang wrote:Been going back and forth about what to build engine wise for the jet boat this year. Currently it is a 466" with a weiand tunnel ram, two 750s, iron cj's, logs and the wrong cam. I have debated doing a 557 with the same top end and a custom solid flat cam. Keep the logs (hardin long bolts)
I have considered a 532 with scjs and sell the iron heads.
I am also considering a forged 500" with twin turbos through the logs. That eliminates the scavenging problem. I can fab everything and do a ms3 myself but it is really more than the jet can handle so it opens a can of worms..
I have been looking for a used set of water jacketed cmi or lightning bbc headers for a while to help but the question is, what combo would you do and is it possible through cam timing changes to make decent power through the logs with a big inch combo?

Unless it is supercharged / turbocharged ... use the longer stroke in a jet boat application.

What kind of jet? What hull? What rpm and impeller are you hoping to turn?
To answer your question about getting power out of the logs, the simple answer is you can't have your cake and eat it too. Log manifolds on boats, especially wet, are always the Achilles heel when it comes to making power. A turbo is about the only scenario where you can get away with them, but even so...
Also remember; the engine doesn't know what it's in, whether it's a boat or a dump truck. Design the engine to make the power you want in the rpm range you want. There are build details specific to a marine open cooling system but since this isn't your first marine engine I'll assume you know some about that.

What size impeller? Does the pump have an inducer?

Scott Foxwell wrote:
Also remember; the engine doesn't know what it's in, whether it's a boat or a dump truck. Design the engine to make the power you want in the rpm range you want. There are build details specific to a marine open cooling system but since this isn't your first marine engine I'll assume you know some about that.

However, every engine build will perform differently when put into different situations so, whatever the build, it must be aimed somewhat correctly for that particular application.

I have personally reconfigured somebody else' jet boat builds because of this.  They build great torque and horsepower for that RPM range the owner wants for a certain MPH but, they don't make enough lower speed torque to ever get past that hole in order to reach the RPM their owners were hoping to achieve.

It does not seem like that will be an issue here, though.

rmcomprandy wrote:

Scott Foxwell wrote:
Also remember; the engine doesn't know what it's in, whether it's a boat or a dump truck. Design the engine to make the power you want in the rpm range you want. There are build details specific to a marine open cooling system but since this isn't your first marine engine I'll assume you know some about that.

However, every engine build will perform differently when put into different situations so, whatever the build, it must be aimed somewhat correctly for that particular application.

I have personally reconfigured somebody else' jet boat builds because of this.  They build great torque and horsepower for that RPM range the owner wants for a certain MPH but, they don't make enough lower speed torque to ever get past that hole in order to reach the RPM their owners were hoping to achieve.

It does not seem like that will be an issue here, though.

Which is exactly what I said and is the case for any engine. The engine doesn't know what it's going in. The engine builder does...
I built and drag raced a 9 sec jet boat and built a lot of "jet boat" engines. Couple have won championships. They're just engines. Decide how much power you want, what rpm range you want it in, and build accordingly.

Scott Foxwell wrote:

rmcomprandy wrote:

Scott Foxwell wrote:
Also remember; the engine doesn't know what it's in, whether it's a boat or a dump truck. Design the engine to make the power you want in the rpm range you want. There are build details specific to a marine open cooling system but since this isn't your first marine engine I'll assume you know some about that.

However, every engine build will perform differently when put into different situations so, whatever the build, it must be aimed somewhat correctly for that particular application.

I have personally reconfigured somebody else' jet boat builds because of this.  They build great torque and horsepower for that RPM range the owner wants for a certain MPH but, they don't make enough lower speed torque to ever get past that hole in order to reach the RPM their owners were hoping to achieve.

It does not seem like that will be an issue here, though.

Which is exactly what I said and is the case for any engine. The engine doesn't know what it's going in. The engine builder does...
I built and drag raced a 9 sec jet boat and built a lot of "jet boat" engines. Couple have won championships. They're just engines. Decide how much power you want, what rpm range you want it in, and build accordingly.

Don't break your arm - Do you understand EVERYTHING which I said...?
A lot of people build water jet engines to have enough power between 6,000 & 7,200 RPM for that speed which they want to achieve however, can't get it past 5,400  RPM because there is not enough power down at that point to get past there.

I guess you presume you are the only person on here who has built championship jet hydro, jet tunnel, jet flat-bottom and jet river racer engines ... NOT.

6t6, I'll tell you the only BBF wet log story I know:

Big azz Glastron/Carlson CVX-20 Boat - Pump gas 521", CJ/SCJ iron heads, middling hyd. flat tappet, Victor manifold w/QFT 950 carb. Berkley, blueprinted, Full "A" impeller and inducer.
Performed great and was a super fun deal. Before someone ask why was this that or another used....sometimes people have 'stuff' that are bought and paid for that ain't perfect but, are not crap either.    

A few years later a set of bowl blended TFS 290 heads were installed. All other engine parts were the same and the at WOT max RPM went up 300 rpm.
An "AA" impeller was installed and the engine 'loss' that 300 rpm....boat ran the same MPH and left like it had a 200 shot of spray on it

rmcomprandy wrote:

Scott Foxwell wrote:

rmcomprandy wrote:

Scott Foxwell wrote:
Also remember; the engine doesn't know what it's in, whether it's a boat or a dump truck. Design the engine to make the power you want in the rpm range you want. There are build details specific to a marine open cooling system but since this isn't your first marine engine I'll assume you know some about that.

However, every engine build will perform differently when put into different situations so, whatever the build, it must be aimed somewhat correctly for that particular application.

I have personally reconfigured somebody else' jet boat builds because of this.  They build great torque and horsepower for that RPM range the owner wants for a certain MPH but, they don't make enough lower speed torque to ever get past that hole in order to reach the RPM their owners were hoping to achieve.

It does not seem like that will be an issue here, though.

Which is exactly what I said and is the case for any engine. The engine doesn't know what it's going in. The engine builder does...
I built and drag raced a 9 sec jet boat and built a lot of "jet boat" engines. Couple have won championships. They're just engines. Decide how much power you want, what rpm range you want it in, and build accordingly.

Don't break your arm - Do you understand EVERYTHING which I said...?
A lot of people build water jet engines to have enough power between 6,000 & 7,200 RPM for that speed which they want to achieve however, can't get it past 5,400  RPM because there is not enough power down at that point to get past there.

I guess you presume you are the only person on here who has built championship jet hydro, jet tunnel, jet flat-bottom and jet river racer engines ... NOT.

No, I thought maybe that was you...
So you can talk about what you did and share your experience and that's OK, but when someone else does it, it's patting them self on the back?
Darn...I forgot to ask permission again.
Get over yourself Randy. You're basically saying the exact same thing I am. Build the engine for the rpm and power you need. If you need power over a 3000rpm range then build it that way, I don't care what the engine is in, right?
And FYI there is a HUGE difference between 6000 and 7200 in both the impeller and engine in a jet so, no, I really don't understand EVERYTHING your'e saying.
Do you?
And "championship" jet hydro and jet flat bottom? LOL...Really? What's a "champion river racer"? You don't have a clue, do you.

Scott Foxwell wrote:
And "championship" jet hydro and jet flat bottom? LOL...Really? What's a "champion river racer"? You don't have a clue, do you.

All those venues DO sometimes require different characteristics in the shape of their power curves.

www.jetboatracing.com/index2.htm

I think you could be one who must be short on clues about that stuff.  

https://www.youtube.com/watch?v=ih4ApJ1lcoc

Nothing further said here will be productive.

rmcomprandy wrote:

Scott Foxwell wrote:
And "championship" jet hydro and jet flat bottom? LOL...Really? What's a "champion river racer"? You don't have a clue, do you.

All those venues DO sometimes require different characteristics in the shape of their power curves.

www.jetboatracing.com/index2.htm

I think you could be one who must be short on clues about that stuff.  

https://www.youtube.com/watch?v=ih4ApJ1lcoc

Nothing further said here will be productive.

You didn't say white water river racing. Different animal all together. Very cool venue.
Jet hydro's and jet flat bottoms don't work and no one races them.
And the productivity stopped with your second post.

6t6mustang wrote:Been going back and forth about what to build engine wise for the jet boat this year. Currently it is a 466" with a weiand tunnel ram, two 750s, iron cj's, logs and the wrong cam.

I have debated doing a 557 with the same top end and a custom solid flat cam. Keep the logs (hardin long bolts)

I have considered a 532 with scjs and sell the iron heads.

I am also considering a forged 500" with twin turbos through the logs...

...but the question is, what combo would you do and is it possible through cam timing changes to make decent power through the logs with a big inch combo?

When it comes to the typical jet boat with a little ol' 460, I've swapped out iron CJs for ported D0VE heads numerous times and the engine has always run much better.  The D0OE-R CJ head is a lot of head for the small displacement 460 given the typical rpm range they operate in most runabout jet boats. So if you're going to keep the iron CJs then the 532 or 557 is the way to go, and if you're keeping the logs then in most cases it's better so choose the smaller displacement 532.

A 532 with well ported iron CJs can be cammed to run just fine in a jet boat with logs/snails.  Sure, you might be able to generate a bigger hp number on a dyno with a different cam, exhaust, etc, but that's not what you're building. If you can let go of "biggest, best, fastest," also forget about specific hp numbers, and instead focus on simply building an engine that will move your boat in the manner you want then in most cases the parts you have can probably get the job done.

But first you ought to post just what you want your boat to be able to do...

So much for the jetboat thread...........

Lem Evans wrote:So much for the jetboat thread...........

OP must have been drinking or something. He wore this subject out, got all his answers and looks like he built an engine back in 2014. Plus, he's "owned a speed shop, a fabrication business and been building engines all (his) life." Not sure why he even bothered to ask.

Hi guys, I didn't get any updates on this thread and checked in tonight. Wow, i appreciate the response. It is a spectra 19, berkley jc-a with a straight "a" impeller, stuffed and clearanced, no inducer. Yes, i overcammed it when i put it together and hit the water wall. The dooe-r heads are too big for it currently. They flow 380s /200s and have 67cc chambers. The wet logs are a love-hate relationship my wife and kids love the fact that they don't have to worry about getting burnt and they're not excessively noisy and I hate the fact that they hamper the engine's performance, what are you gonna do..
It does 60 mph now at 4800 rpm. I thought 80 would be a good target.
Yes I have built a lot of engines, but understand I don't know everything, and also understand the value of the input of the gentleman who are responding to this thread. I have read countless threads on this forum and others about jet boats trying to figure out everything I can about my new toy, so I appreciate any insight that you guys have on this subject..
I am one of probably three Ford powered jet boats in my area all the rest are big block Chevy and big block Oldsmobile, help a brother figure out how to stay out front. ( so far the Oldsmobiles can't keep up )

Paul Kane wrote:

6t6mustang wrote:Been going back and forth about what to build engine wise for the jet boat this year. Currently it is a 466" with a weiand tunnel ram, two 750s, iron cj's, logs and the wrong cam.

I have debated doing a 557 with the same top end and a custom solid flat cam. Keep the logs (hardin long bolts)

I have considered a 532 with scjs and sell the iron heads.

I am also considering a forged 500" with twin turbos through the logs...

...but the question is, what combo would you do and is it possible through cam timing changes to make decent power through the logs with a big inch combo?

When it comes to the typical jet boat with a little ol' 460, I've swapped out iron CJs for ported D0VE heads numerous times and the engine has always run much better.  The D0OE-R CJ head is a lot of head for the small displacement 460 given the typical rpm range they operate in most runabout jet boats. So if you're going to keep the iron CJs then the 532 or 557 is the way to go, and if you're keeping the logs then in most cases it's better so choose the smaller displacement 532.

A 532 with well ported iron CJs can be cammed to run just fine in a jet boat with logs/snails.  Sure, you might be able to generate a bigger hp number on a dyno with a different cam, exhaust, etc, but that's not what you're building. If you can let go of "biggest, best, fastest," also forget about specific hp numbers, and instead focus on simply building an engine that will move your boat in the manner you want then in most cases the parts you have can probably get the job done.

But first you ought to post just what you want your boat to be able to do...

Thanks, the other reason i was thinking 4.3 was since it is the same dish piston, if i keep the iron heads, it helps keep compression lower for pump gas.
I basically cruise around with friends and occasionally race other boats for fun.

Lem Evans wrote:6t6, I'll tell you the only BBF wet log story I know:

Big azz Glastron/Carlson CVX-20 Boat - Pump gas 521", CJ/SCJ iron heads, middling hyd. flat tappet, Victor manifold w/QFT 950 carb. Berkley, blueprinted, Full "A" impeller and inducer.
Performed great and was a super fun deal. Before someone ask why was this that or another used....sometimes people have 'stuff' that are bought and paid for that ain't perfect but, are not crap either.    

A few years later a set of bowl blended TFS 290 heads were installed. All other engine parts were the same and the at WOT max RPM went up 300 rpm.
An "AA" impeller was installed and the engine 'loss' that 300 rpm....boat ran the same MPH and left like it had a 200 shot of spray on it

I hear ya lem, losing the weight would be a plus also. What do you think about that afr top end ? You almost can't beat the look of that tunnel ram in a jet boat application but I've been kind of intrigued by doing an AFR top end on a 532/557.

Nobody wants to talk, eh?
Must be more interesting to hear scott and randy bash each other..

6t6mustang wrote:Nobody wants to talk, eh?
Must be more interesting to hear scott and randy bash each other..

TR does have the 'WOW' factor' but I'm over it.

Iron CJ/SCJ heads are not at their best when modest RPM and camshaft lift are in play.....Lose those.

Any luck getting the afr heads these days, if not I was inbetween scj and tfs streets

I am currently in the process of putting an engine plan together as well, so any input is appreciated.

I have a 1984 Condor Sprint - It had a perfectly good Chevrolet in it, but I am not a chevy guy (it is for sale if you know anyone interested).  I have a bone stock 460 short block in the machine shop getting checked out.  I will be running log manifolds (this boat is one of 4 built with the engine cover).  I am looking for 600 reliable HP with torque to come out of the hole with a AA impeller (Dominator pump, ride plate, inducer and diverter). My max RPM range goal is 5500.  95 percent of the time I would like to cruise around 3500.  What will be my best bang for the buck budget build to get to these numbers?  Is it doable with D0VE heads, ported D3's or do I need to look into aftermarket?  Do I need to go ahead and look at the stroker kits or can it be done with a stock crank, stroke? Finally, I would like to run no more than 94 octane - so max compression at 10 to 1?

I'm not trying to hijack your thread - I figured since I too am building a jet boat engine. That I would jump in.

Thanks guys - I appreciate it.

Well, got the scat 557 kit sitting in the shop. Internal balance. Thinking about unloading the dooe-r's if i find a buyer..

6t6mustang wrote:
Thanks, the other reason i was thinking 4.3 was since it is the same dish piston, if i keep the iron heads, it helps keep compression lower for pump gas.
I basically cruise around with friends and occasionally race other boats for fun.

WoW ... so many different applications wanted.
You ought to keep a fully stocked freezer on board and sell ice cream on the side, too.

Randy, I'm gonna UPS (you) an ice cream

You know, I would bet my last $ that if you and Jeff met at the bash and set down to shoot the crap, you would get along great.

Your both on the same page, but can't seem to find common ground.

I'm glad to have both of you on this forum..............

rmcomprandy wrote:

6t6mustang wrote:
Thanks, the other reason i was thinking 4.3 was since it is the same dish piston, if i keep the iron heads, it helps keep compression lower for pump gas.
I basically cruise around with friends and occasionally race other boats for fun.

WoW ... so many different applications wanted.
You ought to keep a fully stocked freezer on board and sell ice cream on the side, too.  

hey, I got nothing to prove..
but, thanks for the great info pops.. your posts are always worth the read..