SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: Handyman on July 09, 2015, 12:36:43 PM
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Over the 4th i took my 21ft centurion mini day Cruiser for the 4th time size I got it and played on the lake.. I haven't really beat on it since I was still testing for any more engine issues( had a few hidden issues that arose when I took it out and got towed back in).. Well I decided to be a little more rough with it and see what issues a may find...
I got out of the no wake zone and smashed the throttle.. Engine sounded good and the bow went towards the sky and stayed there longer than expected but none the less the boat finally got on plane and took off.. I'd say it took a good 30 seconds to get on plane... Once it was on plane I held the throttle as far as it could go and noticed the RPMs stopped at 4500rpms.. I guesstimate I was going about 60mph. ( my buddy in his bayliner said I started pulling away from him at 55mph)... So here's my question
Would a bigger cam help in getting more RPMs and making the engine run better to helping getting on plane quicker?
Next question is... Will a high manifold help in power or not? Never really dealt with high rise manifolds..
Engine is a 454BBC with a Holley 750dp... Don't know the specs on the cam
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Just throwing parts at any engine hoping for more power is a shot in the dark. You have to know what you’re working with first and then carefully match all components, not one or two or even three items are responsible for producing power. Larger cam’s require better quality cylinder heads and usually higher compression to gain power. All induction systems also have to be matched to what RPM and application is being asked from any engine. It’s the entire combo that’s responsible for producing power, look at it this way, the induction and exhaust have to hold hands through a good design of heads and then accompanied by proper valve timing events to fill and empty each cylinder properly and yet have the highest volumetric efficiency to produce power. Remember, an engine is a tool, used to extract and harness heat energy out of a liquid fuel. To make more power an engine has to handle the fuel better (atomization) and be able to burn more of it on the power stroke. To really answer all questions like yours without guessing, an engine MUST be on a dyno, that’s where parts and other combinations can be tried to find out witch works best. Then dealing with drive unit, prop pitch or jet pump spec’s is a whole other topic.
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Going down a completely different road here.
What rpm were you seeing while attempting to plane? If the same or similar 4,500rpm, stop right there. Horsepower is not the issue.
How much shit did you have in the boat? See it all the time, get a day cruiser, fill it with a cooler, a bunch of water toys and five corn fed rednecks and the token hottie or two and you can't get the tub to work.
Do you have a Place Diverter and where was it set?
Workout a doubt, a Diverter is the single most best bang for the buck addition you can make to a cruiser. Even if you buy new.
Leave the engine alone, 4,500 seems fine for what you are describing.
You have something fundamentally wrong if your boat takes more than three seconds to plane.
And just answer your direct question, no. An intake and carb is not going to fix anything.
JMO
GT
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So 4500 rpm? 'A' impeller? Sounds like a 330hp 454...thats about right.
Iron intake, peanut port heads, and logs and snails?
The peanut port heads are gonna kill flow. Iron intake doesn't help either. truck flat tappet cam.
Need more info
Where do you want to be?
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I've got a 21 Bahner mini cruiser, RPM and speed I'm seeing about the same.
Takes me a few seconds to get it up on plane. Some of it I have figured out over time, is weight distribution. If I have all seats full, I havento move weight forward to get it up on plane quicker.
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Yes peanut port heads, logs and snails, I general run of the mill intake, no diverter Berkeley pump with "A" impeller,
Boat had full tanks(40 gal) and just myself and 2 others( about 500lbs)
I'm fine with how the boat runs.. Just surprised at how long it took to plane. I'm not going to start throwing parts at it just to make it plane quicker, well not until winter comes around... Just looking to see if it's totally normal for a heavy mini day to take so long to plane and if not what should i be looking at to try to find the culprit... I will try to get out to the lake in the next few days and take a video of what I'm describing so you can see for yourself
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Check that the reverse gate isn't 'falling down' when you hit the throttle.
Bow tank? or saddle tanks?
Sounds like a shoe, ride plate, and diverter are in your future.
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Saddle tanks.. I do have a little play in the reverse bucket cable but i checked it on the trailer and it doesn't fall down once it's open..I'm looking at getting a diverter but the wife has cut but spending on the boat for now
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Saddle tanks.. I do have a little play in the reverse bucket cable but i checked it on the trailer and it doesn't fall down once it's open..I'm looking at getting a diverter but the wife has cut but spending on the boat for now
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A Diverter costs less than carbs and intakes...
FWIW.
GT
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I know but the wife said she don't care
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I know but the wife said she don't care
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How much is a new wife going for these days?
DOH!
J/K
GT
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ROFL... I have to give in for now... She didn't kill me when she came home and found this in the garage...
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