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baja350

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Newb 350 Chevy Jet Boat Build
« on: September 20, 2017, 06:38:55 PM »
Hi Guys!

I am brand new to the forum and needed some advice. I just got a jet boat last summer and it needs some motor work. It is a Baja 190BR with a 350 Chevy (although the tag on the engine says 454, it is not a big block). The motor is pretty tired, it has low compression and it doesn't have much kick anymore. And now on top of it my jet pump (which is a Berkley 12JE) has started growling so I pulled the boat out of the water to avoid causing more damage. Also, before it started making noise I suspected that it was not efficient anymore. This tired 350 was able to spin the "A" impeller to almost 5000rpm. According to the Berkley impeller chart it would need some real HP to do that kind of RPM. I have all the maintenance records for the boat since the early 90's. The last owner had the jet pump done about 8 years ago. So I imagine it is time for it to be rebuilt.

Any info you guys can give would be awesome!

- I want to build the 350 while it is out of the boat. My goal is around 400HP. Will the normal 2 point engine mount (which connects to the standard motor mount points on the block to the stingers) be okay for that horsepower limit?

- Do I need forged pistons? I want to do this on a budget so the less forged hardware would be nice on my wallet.

- For this level do I need to do anything to the cylinder heads? Such as different valve seats?

- What intake would be recommended? Single plane or dual plane? Any recommendations on Camshaft specs or cylinder heads?

- For this power what impeller would be best? I think a "B" or a "B/C" would be best. Most of what we do is cruise and blast around. What about adding an inducer?
 
- When rebuilding the pump should I use normal wear rings or stepped wear rings?

Thanks guys!
« Last Edit: September 20, 2017, 08:27:52 PM by baja350 »
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Re: Newb 350 Chevy Jet Boat Build
« Reply #1 on: September 21, 2017, 12:56:27 PM »
first it would be nice to know the block and head #'s before deciding on parts.

400 hp? no problem:

ZZ5:
https://www.summitracing.com/parts/nal-19301294

Cut impeller accordingly:

http://www.jetboatperformance.biz/pages/calculator.html

Dan'l

And welcome to the boards
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NMMiller

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Re: Newb 350 Chevy Jet Boat Build
« Reply #2 on: September 21, 2017, 01:24:23 PM »
Depends how much you're wanting to spend. If you think the engine is going to be close to 5k then spend the extra money and order the GM604 crate. $6,200 and makes 400hp 400ft/lbs. simply put awesome motor. We run them in circle track and you can't hurt them. We turn the 6,800rpm


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NMMiller

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Re: Newb 350 Chevy Jet Boat Build
« Reply #3 on: September 21, 2017, 01:26:57 PM »
Depends how much you're wanting to spend. If you think the engine is going to be close to 5k then spend the extra money and order the GM604 crate. $6,200 and makes 400hp 400ft/lbs. simply put awesome motor. We run them in circle track and you can't hurt them. We turn the 6,800rpm


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https://www.speedwaymotors.com/Chevrolet-Performance-19318604-CT400-IMCA-Seal-604-Chevy-Crate-Engine,71387.html


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86caribbean

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Re: Newb 350 Chevy Jet Boat Build
« Reply #4 on: September 21, 2017, 03:21:30 PM »
These crate engines, as with most, are not designed for a marine application, it states this right in the description of the engine. The internal clearances are not set up loose enough to allow for thermal expansion of certain internal components while running an open cooling system.
  • Boat #1: 1986 18' Caribbean
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Re: Newb 350 Chevy Jet Boat Build
« Reply #5 on: September 21, 2017, 03:31:11 PM »
SHHHHH.... The motor doesn't know its in a boat....

Dan'l
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baja350

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Re: Newb 350 Chevy Jet Boat Build
« Reply #6 on: September 21, 2017, 04:27:04 PM »
I wish that is how it worked!  :'(

From everything I know the piston to wall clereance and even some times the valve guides have to be different.

My goal is to try and find a good machine shop not to far and have them do that part.
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greg511

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Re: Newb 350 Chevy Jet Boat Build
« Reply #7 on: September 22, 2017, 09:32:48 AM »
These crate engines, as with most, are not designed for a marine application, it states this right in the description of the engine. The internal clearances are not set up loose enough to allow for thermal expansion of certain internal components while running an open cooling system.
Why dosent anyone run a thermostat with a pressure regulator ? I did with my first boat it run at 170 all the time and never had any problems. Got the kit from rex marine.

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Re: Newb 350 Chevy Jet Boat Build
« Reply #8 on: September 22, 2017, 10:35:27 AM »
Why dosent anyone run a thermostat with a pressure regulator ? I did with my first boat it run at 170 all the time and never had any problems. Got the kit from rex marine.

Sent from my SM-G950U using SoCal Jet Boats mobile app

Why run 170*? Cooler engines make MORE Horsepower.

I run 130-ish. 140 at the dock/no wake zone.

Dan'l
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