Hi,
I'm new to socal jet boats and fairly new to jet boating. I have a big block chevy casting # 10114182 and head casting # 10114156. According to info I have found the heads are "peanut port heads." There's a lot of conflicting info on whether these are good heads for boats. Just wanted to know of anyone that could give me some insight. Thanks.

Crewchief22 is right, everything in an engine boils down to what you want from the engine, it's just a tool, the question is designing the right tool for the job. In my opinion all the BBC heads have potential, but there are some that have a whole lot more. I actually have the peanut port heads on my engine, my casting #'s are 346236 from 1976. I put some work into them like opened up the intake port vol. to 244cc and the exh. to 122cc and added the larger valves 2.190IN. and 1.880EX. I didn't set out to build a race boat, but wanted to build a respectable engine on a fair budget. I have a healthy .060 over 454, 10.0:1, tunnel ram, two 600cfm vac. Holley's, MSD, Comp Cams hyd. flat tappet cam .580/245 @ .050 and so on, I dynoed this engine and with these heads it made 542hp @ 6,000 and 522tq @4,100. When I tried to pull past 6,000rpm power fell off fast due to port saturation (heads couldn't flow any more air). With these smaller oval port heads the engine made allot of low end grunt like 507tq @ 3,600. I have a decent pump set up and at WOT I see 5,600rpm and in the mid 70's for mph, again it's not a drag boat, but it's fun and reliable.

Thanks for the responses. I definitely don't plan on it being a race boat by any means. It's a mini day cruiser I plan on a nice little family boat. I just pulled the engine for an oil change and thought I'd research things. My dad has a 91 ultra 21'  with a mercury 350, but it's an i/o and his boat is just about as fast as mine with a 454 big block. With the info I found on my engine Everyone seems to say the heads are only good for towing application. I don't understand why his smaller engine in a bigger boat could keep up with mine, a bigger engine in a smaller boat.

The difference is easily explained.

A jet boat survives on a jet of water pushed out the back of a hull.
A prop boat is pushed by a propeller at a much lower and positive point. 

My last I/O boat had a small block in it and ran in excess of 65mph, with four people,  a dog and a cooler full of beer and soda. If you are looking to have that same performance in a jet, you will need to make well over 600hp and have the set up totally dialed in. Not to mention burn nearly three times the fuel.

One way you need to look at this that is somewhat eye opening.

On a hull such as yours, it would take a huge gain in horsepower to  make even a modest difference in performance.

To put it in perspective,  a peanut port headed 454 makes very close to 330hp in stock form.

Heads alone might be good for another 30hp. (Even that is a stretch) to make the heads work, you would need a cam change, bigger carburetor, different manifold, potentially larger fuel pump, different exhaust,   just to see the potential of the heads. This leaves the compression ratio stock (probably 8.8:1) with likely cast pistons and crank. You will barely notice a 100 hp gain (maybe another 5mph), which you still will not have with the above mentioned mods.

So in short, spend a bunch of money to break it. Woohoo...

I would leave her the way she is while scrounging parts and pieces to build a killer (if that is what you really want). This way you get to enjoy the boat while you build a different motor.

Good hunting.

GT

The difference is easily explained.

A jet boat survives on a jet of water pushed out the back of a hull.
A prop boat is pushed by a propeller at a much lower and positive point. 

My last I/O boat had a small block in it and ran in excess of 65mph, with four people,  a dog and a cooler full of beer and soda. If you are looking to have that same performance in a jet, you will need to make well over 600hp and have the set up totally dialed in. Not to mention burn nearly three times the fuel.

One way you need to look at this that is somewhat eye opening.

On a hull such as yours, it would take a huge gain in horsepower to  make even a modest difference in performance.

To put it in perspective,  a peanut port headed 454 makes very close to 330hp in stock form.

Heads alone might be good for another 30hp. (Even that is a stretch) to make the heads work, you would need a cam change, bigger carburetor, different manifold, potentially larger fuel pump, different exhaust,   just to see the potential of the heads. This leaves the compression ratio stock (probably 8.8:1) with likely cast pistons and crank. You will barely notice a 100 hp gain (maybe another 5mph), which you still will not have with the above mentioned mods.

So in short, spend a bunch of money to break it. Woohoo...

I would leave her the way she is while scrounging parts and pieces to build a killer (if that is what you really want). This way you get to enjoy the boat while you build a different motor.

Good hunting.

GT

Being a n00b to the jet world I don't mean to step in and flaunt ignorance about the subject of jets vs I/Os or hull vs power, etc.  I am fairly experienced in automotive engines, though.  Here's what I do know...

Peanut ported (late 80s, early 90s) 454s were factory rated in trucks at around 230hp, 385tq with a 7.9:1 compression ratio.  HP rating is similar to later model 5.7 "Vortec" engines found in many I/O setups.  Adding a set of early closed chamber oval port heads, decent cam and intake will bump the compression up to about 9:1 and get you around 400hp.  Pretty decent gains and still a fairly mild engine.  I can't speak as to what kind of MPH gains you'll see in a jet... but in a car 170hp is a helluva kick in the seat

 

Thanks for more information but like I was saying I don't have much engine building skills and I can't afford taking it to a shop to do the work so looks like I'll just keep it stock for awhile.
What if I was to take out the big heavy 454 and put a small block in it with the same horse power?  Would I get the same mph with less fuel consumption?

Thanks for more information but like I was saying I don't have much engine building skills and I can't afford taking it to a shop to do the work so looks like I'll just keep it stock for awhile.
What if I was to take out the big heavy 454 and put a small block in it with the same horse power?  Would I get the same mph with less fuel consumption?

This is going to sound stupid, but hp is hp.

The fuel is the fuel hp for hp.

The problem with a mouse is that it will likely need to spin a buttload of rpm to get the same hp. This drops pump efficiency.

In short. No. Imo.

GT

http://www.sterndrives.com/merc/sternspecs.html

This is real current so they don't show a 4 barrel carburetor, just tbi and mpi. A four barrel carburetor is good for an additional 25hp.also, check the c/r.

GT

Thanks for that link.  Interesting that Mercury rates them 100hp higher than GM did.  Makes me wonder if there are actually any differences or if they're tested differently.  Any thoughts on that?

The main point I was trying to make is that the truck engines can be woken up significantly with a H/C/I swap.  100+hp with inexpensive components is quite doable

Smog for one, restrictive (read quiet) exhaust, and all the accessories draw major power, all that is taken into account when rating.

I still say, with heads only, 30 HP would be a major stretch. That would make it a 350 hp engine. The Ass-O-Nometer would barely flinch.

JMHO.

Be an interesting experiment though. Do it in stages:

Heads
Cam
Rocker ratio
Intake manifold
Exhaust
Carburetor
Ignition
Pump work


And document the results at each stage.

That would be sweet.

GT

Sent from my SCH-I545 using SoCal Jet Boats mobile app

100% agree that heads only won't get you much if you're still running a stock cam and intake.  Stock parts are matched to work together so when you change one the rest need to be changed to match.  It's all about the combo of parts working together. 

Quick example that we still laugh about today... A couple decades ago when we were young and dumb my buddy thought it'd be a good idea to pull the closed chamber oval ports off his otherwise stock 396 and replace them with ported, big valve, open chamber oval port Merlins.  He was then surprised at what a dog the motor was after spending $2k+ on heads.  Not only did compression drop through the floor, port velocity was way down at low RPM.  It added up to a major loss of low end with a very mild gain up top... not exactly what you need to move a '66 Impala!  LOL!  Heads alone didn't gain him anything... but if he had been able to keep his compression, add a decent cam, intake and headers then he would have had a beast on his hands.  Those heads went on to make 600+ hp on a different motor with a solid roller cam.  It's all about that combo