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LarsJensen

320 engine performance mods

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LarsJensen

Hi BU crew

I'm more of a "if it ain't broke, don't fix it" kind of guy but The curiosity is getting the better of me. I just acquired a 2006 Sunscape with the base 320 engine. Has anyone had any success with some performance enhancing upgrades? I'm aware of the full array of prop options, so I'm wondering more about tinkering with the engine itself(increasing horsepower).  My goal is just to learn what's out there, what's possible, and what would be worthwhile and fun to do. 

Thanks in advance!

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WAwinegrapes

check out Jegs.  They sell blower kits for chevy small blocks.  and NOX!

 

 or:  http://www.gmpowertrain.com/marine.html  along the right border, the blue box "products"

Edited by WAwinegrapes

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Nitrousbird

Simply put, you will find a pile of threads like this one and no one doing anything to actually make more power.

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MalibuNation

Changiing the prop is what most of us are going to recommend depending on you needs.

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MadMan

On mine, the simplest a cheapest performance improvement was bumping the ignition timing.  GM/Indmar was very conservative on this, the total advance added during wide open throttle is 20 degrees, added to the initial 10 only gives 30 degrees.  I bumped mine 5 degrees.  While I have no measured data, it should improve both power and fuel economy. Yours might be different being a few years newer. 

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Michigan boarder
11 hours ago, LarsJensen said:

Hi BU crew

I'm more of a "if it ain't broke, don't fix it" kind of guy but The curiosity is getting the better of me. I just acquired a 2006 Sunscape with the base 320 engine. Has anyone had any success with some performance enhancing upgrades? I'm aware of the full array of prop options, so I'm wondering more about tinkering with the engine itself(increasing horsepower).  My goal is just to learn what's out there, what's possible, and what would be worthwhile and fun to do. 

Thanks in advance!

What is your budget?  If you are only doing external changes, you can add air in (different intake) and out (different manifolds & exhaust).  HP gains can come from doing that to a small extent.  Changing the cam will help.  Of course, any time you do these things the fuel delivery (injection/ECM) probably needs to be changed as well.  Really the sky is the limit, so it points back to $$.  So....what is the budget?

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Chatty21VLX
4 hours ago, MadMan said:

On mine, the simplest a cheapest performance improvement was bumping the ignition timing.  GM/Indmar was very conservative on this, the total advance added during wide open throttle is 20 degrees, added to the initial 10 only gives 30 degrees.  I bumped mine 5 degrees.  While I have no measured data, it should improve both power and fuel economy. Yours might be different being a few years newer. 

This is probably the easiest and cheapest thing you can do. 

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LarsJensen
3 hours ago, Michigan boarder said:

What is your budget?  If you are only doing external changes, you can add air in (different intake) and out (different manifolds & exhaust).  HP gains can come from doing that to a small extent.  Changing the cam will help.  Of course, any time you do these things the fuel delivery (injection/ECM) probably needs to be changed as well.  Really the sky is the limit, so it points back to $$.  So....what is the budget?

I would venture to guess a budget of 3-4K. 

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boardjnky4

Depending on the MEFI version you have in your boat, there are tuning options. You'd need an experienced engine tuner to make any changes.

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shawndoggy

the fact that the OP's 350 is the LCR (no knock sensors) is also going to limit the safe range of tunability even if mefi-burn is an option.

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MadMan
18 minutes ago, shawndoggy said:

the fact that the OP's 350 is the LCR (no knock sensors) is also going to limit the safe range of tunability even if mefi-burn is an option.

Interesting, I guess the pulled them out for a cost savings.

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MadMan

Something to think about, all the standard methods to increase your horsepower are ways to keep the torque from falling off at higher rpm.  This gives you the added horsepower, but it's only available at that higher rpm. It's useful for barefooting or that top end run, but doesn't really help for wakeboarding or surfing, unless you're turning 5000+ rpm during these activities.

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jjackkrash

It is your boat and your money, but I just don't see upside.  Increased cost, marginal gains, long-term reliability risks, etc.  $3-4k could get you a kick-a** stereo, duel battery, and shore-power charging system, however, if you spent wisely.   

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Woodski

@LarsJensen:  There are several mods you could consider depending on your objectives.  As Michigan Boarder noted, getting more air in & out are the keys.  If you don't want to consider a supercharger, a few items to jump the HP level:  higher flowing cylinder heads (Fast Burn 385 as an example), hotter camshaft (be careful not to overcam as low end power is still critical, so something like a GM ZZ4 cam, the current GM marine cam is very good) or increase the rocker arm ratio to a 1.6; on the exhaust side, a freer flowing exhaust manifold (various options) coupled to a larger diameter exhaust system, on the ignition side, optimizing the spark advance for best power.  If you go that route and have fuel injection, you will need to match up the injector flow to the airflow increase.  To answer your question, yes.  I did a top end & camshaft upgrade on a 265 Hp Merc with very satisfactory results.  Also, check Michigan Boarders various threads on his engine upgrade.  A small block can easily be upgraded to ~375-400 Hp and still have plenty of low end power/torque, it just depends on what your goals are.

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WAwinegrapes

If you look at some of the other comments posts and comments.  You need to increase HP and TQ signifiacntly to notice any  measurable improvement in performance.  and adding all that HP and TQ will diminish the life of trannies and other drivetrain issues.  Exactly what jackrash said.

 

If you can, take a ride in a Malibu with the monsoon 409 and 427.  If you could measure, there would be neglible difference between the 2 engines.  and even going with the SC engine, there would be neglible difference until you get to 4-5,000+ rpms. and how often are you running in the 4s and 5000s rpm range?

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Michigan boarder

I feel like such a baller when @Woodski references me on an engine thread.:notworthy:

@LarsJensen do you have a guy or guys that know engines and can get into this stuff with you?  If not, I'd say don't mess with it, I was lucky to have some guys that knew what they were doing do the internal & complicated work and developed an engine design while I did the bolt on/off stuff.  One thing that has not been asked is why do you want more power? (I know, kind of a stupid question)  Is the current engine limiting your activity, holding you back from something?  If so do you feel you need more low end power or top end power?

Obviously you can re-prop, but that can be a PITA, like if you want to surf and then someone says "let's barefoot!" and you don't want to mess around with changing out a prop while a crew is in the boat on the middle of the lake.

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LarsJensen
4 hours ago, jjackkrash said:

It is your boat and your money, but I just don't see upside.  Increased cost, marginal gains, long-term reliability risks, etc.  $3-4k could get you a kick-a** stereo, duel battery, and shore-power charging system, however, if you spent wisely.   

Good points! 

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LarsJensen

Thanks all for the input. Was just curious. I'm sure the sky is the limit with ones pocketbook a close second. 

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