SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: 78millerjet on February 17, 2016, 01:52:24 PM
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Im new to the forums and a noob on engine mods. I have a 78 miller 20 ft mini cruiser with the bone stock 460 with log manifilfst. I believe top speed is 54 @ 4400rmp. She's a well built full stringer boat and a bit heavy. Besides an intake manifold electronic ignition speed grate and diverter, what will she need to reach 70? .I would be happy with an honest 65. Thx!
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More hp :) is the pump good?
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Enjoy it as a cruiser. That is what she was made for. It wouldn't be money well spent trying to get there. If you want to go 70+ get a smaller boat with more ponies. Better bang for the buck.
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More hp :) is the pump good?
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Dont give him false hopes. Lol
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Dont give him false hopes. Lol
Oh yeah that's right, my "400" hp boat will only go about 30 haha
Fordlover is right though, cruisers are best as just that.
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Pump is good. I believe its an A impeller. Sounds like 10 mph is unrealistic for 2k? Its a 9 out of 10 cosmetically and she's a keeper. If I cant get her to 65 ill leave her stock
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What heads, cam, and manifold is it running or are you planning on running?
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Thanks for the replies!
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We are happy to help! The real pros will respond soon.
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And post some pics. We like pics
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Its bone stock.. was thinking aftermarket intake manifold electronic ignition speed grate and diverter would wake her up a bit. About the only thing I do know about jets is it takes alot of hp to go fast
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The torker manifold is a good one, so is the stealth... If it doesn't have dove-c heads, worked on d3's or aftermarket heads you're really leaving a lot of power behind.
You'll get a good amount of power out of just a manifold and heads upgrade. Without a set of good breathing heads the other mods won't do as much.
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The torker manifold is a good one, so is the stealth... If it doesn't have dove-c heads, worked on d3's or aftermarket heads you're really leaving a lot of power behind.
You'll get a good amount of power out of just a manifold and heads upgrade. Without a set of good breathing heads the other mods won't do as much.
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So our intakes are just for looks? I knew it! Shit!
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Its never been apart...I'm sure its a cast 1978 engineering special. Still has points and stock quad carb. Berkeley jet has never been rebuilt either. Its a great custom boat, ill never part with her even for a younger model...
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Pictures?
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From mid 50's 70mph is virtually double the horsepower. So if you're making in the low to mid 300hp range now, it will take near 700 ponies to hit your goal.
Be a lot cheaper and less grief to lower your standards.
JMO
GT
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From mid 50's 70mph is virtually double the horsepower. So if you're making in the low to mid 300hp range now, it will take near 700 ponies to hit your goal.
Be a lot cheaper and less grief to lower your standards.
JMO
GT
That's what's I kept telling my girlfriend about me... Well now fiancé! Winner!
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That's what's I kept telling my girlfriend about me... Well now fiancé! Winner!
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Stick with what works brother.
;D
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Thanks for all the advice guys!
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From mid 50's 70mph is virtually double the horsepower. So if you're making in the low to mid 300hp range now, it will take near 700 ponies to hit your goal.
Be a lot cheaper and less grief to lower your standards.
JMO
GT
Tamsone6 doesnt want to hear that!
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Its bone stock.. was thinking aftermarket intake manifold electronic ignition speed grate and diverter would wake her up a bit. About the only thing I do know about jets is it takes alot of hp to go fast
This is all a really good start, if you shoot for 60mph, I think you will be happier.
The Place Diverter is an automatic 2-3 mph. The ignition upgrade and intake manifold will make it run a little better but I would call it virtually immeasurable speed gains.
A loader grate could be helpful if set up properly.
A bigger part power gain would be found in a camshaft and carburetor swap. This has to be thought out too, the compression ratio and exhaust system needs to be kept in mind when selecting both.
Still stick by my story of needing to double the power to even graze 70 for a few seconds.
$2000, that will get you to 60mph, likely not a whisker more.
JMHO, don't shoot the messenger.
GT
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Fat fingers. Sorry
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Would the torker manifold and msd ignition do anything thing over stock? Figured if she breathes better maybe a bit better fuel economy.. if its best to just leave her stock. I'm ok with that too
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Sorry GT, didn't see your previous response..thx!
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Consider aftermarket aluminum heads. The right set will will bump your compression and breathing ability while lowering weight. You really need to find out what your current compression ratio is.
I'm curious why you are only getting 4400 RPM.
I don't see an intake swap making any positive gain.
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Consider aftermarket aluminum heads. The right set will will bump your compression and breathing ability while lowering weight. You really need to find out what your current compression ratio is.
I'm curious why you are only getting 4400 RPM.
I don't see an intake swap making any positive gain.
With the mentioned budget of $2K, I'm thinking heads will be just a bit out of reach given he really should invest in carburetor, Place Diverter and a loader, not to mention ignition never hurts.
Strictly speaking "Bang for buck".
The next step would be a motor build and if heads are considered that would be the next logical step.
Personally, I don't see him there yet.
As for the 4,400 rpm, thinking just the tune is likely the culprit unless we are speaking altitude or an AA impeller.
But I like the way you think. 8)
GT
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Oh yeah that's right, my "400" hp boat will only go about 30 haha
Fordlover is right though, cruisers are best as just that.
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Sooooooo, thinking out loud here.
You think 400 horses is worth 70?
I would take that bet all day long.
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Sooooooo, thinking out loud here.
You think 400 horses is worth 70?
I would take that bet all day long.
Im making right about 4-450 on motor, and i do 71 on gps :-) lol
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Sooooooo, thinking out loud here.
You think 400 horses is worth 70?
I would take that bet all day long.
Ya know Glenn, a stock ZZ4, 355hp, in the right boat is north of 80...
Dan'l
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Ya know Glenn, a stock ZZ4, 355hp, in the right boat is north of 80...
Dan'l
yep!!! See!!!
butg really in the aspect of this thread. Itll take a LOT more than 400 to see 70 lol
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yep!!! See!!!
but, really in the aspect of this thread. Itll take a LOT more than 400 to see 70 lol
Yep- @ 500 hp+/- , I was at 57-58 in a heavy azz cruiser.
Dan'l
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Yep- @ 500 hp+/- , I was at 57-58 in a heavy azz cruiser.
Dan'l
How dare you go against the Yoda(GT) of jet boats!! You will feel his wrath!
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Sooooooo, thinking out loud here.
You think 400 horses is worth 70?
I would take that bet all day long.
No I don't at all GT, FordLover is just poking fun at me because that's what I get for helping him move 6 yards of rock.
I do however agree that with the aforementioned improvements a goal of 60 is reasonable. The last motor in my boat was pretty mild and I ran high 50's. Just adding my opinion on what I would do to grab a few more mph.
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How dare you go against the Yoda(GT) of jet boats!! You will feel his wrath!
I wanted an honest 60 mph out of mine...$2200 just for the roller cam set-up, best of 57-58 mph up river.
Dan'l
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The 4400 RPM just doesn't sound right. Either you have a weak or damaged engine or it is way out of tune. A 38 year old carburetor and points ignition can be pretty tired by now. Modernizing with electronic ignition won't necessarily get you any more horsepower but it could allow your engine to operate to its true potential. Why would start with getting the engine to its peak state of tune. It needs to run right first!
What intake manifold is on it now that you want to replace with a Torker?
Hardware changes/upgrades really haven't been discussed at this point. A Place diverted, as mentioned, along with a full-droop, back-cut shoe ride plate will free up a few MPH. If the engine is in good tune and the pump is still stalling less than 5K,you might consider cutting the impeller (assuming no mechanical issues).
Unless the engine is hurt, tearing into it will be a can of worms and then you will still be restricted by your exhaust. Hopefully you have the logs that can be opened to the larger outlet.
Speed comes from everything working together and working right. Overlooked and/or disregarded details will cost you performance.
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The 4400 RPM just doesn't sound right.
Why is this? A stock 460 is about 320 hp, spinning an 'A' would be 4500 or so. Again 38 year old stock motor.
Hardware changes/upgrades really haven't been discussed at this point. A Place diverter, as mentioned, along with a full-droop, back-cut shoe ride plate will free up a few MPH.
Agreed, hardware is always important.
If the engine is in good tune and the pump is still stalling less than 5K,you might consider cutting the impeller (assuming no mechanical issues).
320hp Will never see 5K with an A.
Cutting the impeller smaller, for a mini cruiser will suffer out of the hole, and will make a minimal difference on top end.
Unless the engine is hurt, tearing into it will be a can of worms and then you will still be restricted by your exhaust. Hopefully you have the logs that can be opened to the larger outlet.
Logs and snails will support over 500 HP, just not as easy to get there, as with headers.
What intake manifold is on it now that you want to replace with a Torker?
It sounded like a stock 460 cast iron truck manifold. Heavy as an anchor. Any aluminum manifold, especially a single plane would help performance, even more when carb/heads/cam combo is done.
Speed comes from everything working together and working right. Overlooked and/or disregarded details will cost you performance.
Well said.
Dan'l
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Im making right about 4-450 on motor, and i do 71 on gps :-) lol
On a heavy cruiser?
Not.
GT
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On a heavy cruiser?
Not.
GT
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Yes I know lol I was busting your balls lol
Hence the later "not in the context of this thread" lol
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Meant 4600rpm. I hadn't realized how spendy it was to get from 55 to 65.
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Meant 4600rpm. I hadn't realized how spendy it was to get from 55 to 65.
Yeah. It can be. I'd take some of the advice here and atleast modernize everything.
This way it's new, modern, reliable.
Then you can worry about speed after that. You may gain a bit if your components are a little worn or not in the best of shape
Modernize the ignition, intke, carb and see what happens
I know in a car I gained about a half second in the quarter with a msd 6a and billet distributor over an old points deal
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Carb was rebuilt last winter. Engine runs good. Will have to look at stock manifold. At this point a full tune up and new ignition are in order. Maybe have the jet looked over. Its all original so its time
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Carb was rebuilt last winter. Engine runs good. Will have to look at stock manifold. At this point a full tune up and new ignition are in order. Maybe have the jet looked over. Its all original so its time
That's your best plan of attack
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Carb was rebuilt last winter. Engine runs good. Will have to look at stock manifold. At this point a full tune up and new ignition are in order. Maybe have the jet looked over. Its all original so its time
Unless I missed it, I don't see what carburetor it is.
Do you have a list number by chance?
GT
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My fault, I missed the this was a cruiser. With that being said...
I would suggest the Place Diverter HPH over the full droop. You don't have enough horsepower and the boat is too heavy to take advantage of the full droop.
If your engine is in good condition but only needing carburetor and ignition updates, I would budget for a centrifical supercharger that is capable of up to eight pounds of boost combined with a CSU blow-through carburetor and locked out ignition timing. Just one pound of boost will net you more power than any performance modification you can make.
Just a thought.
Cheers,
Joe
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Did we get any pics of the motor or video links posted yet???
Shawn