Reducing engine noise and improving Hp

[Footer613]

Hi all,

I have a 2000 Malibu Response LX ( with manual wedge) with about 650 hours on it.  I am considering adding a Fresh Air Exhaust (FAE) to it to primarily reduce the noise level, since we often slalom and barefoot early in the morning to avoid boat traffic.  Also the Kids surf, so CO reduction would be a good thing.  The concerns are;

1) The boat’s top end is about 44 mph and the FAE may reduce that.  I’ve heard it is about 2 mph.  I prefer to BF at 40 mph, but 42 mph for one footing.  I suspect the FAE may drop the speed into or below that range.  Any thoughts on that. 

2) What is the impact on slalom wake and 90ft back BF wake?  I prefer to slalom at 32 off and 36 off, since those are the sweet spots in the boat’s wake, but interested in any comments on wake changes at all lengths

3)  Are there any modifications I can make to the existing monsoon engine to increase the Hp a bit to compensate for the added FAE drag, …i.e. keep the 44 mph with the FAE?  …ideally solutions that don’t  consume too much extra gas.

 

Regards,

Rob

 

[Slurpee]

I put an FAE on my ‘01 Sunsetter VLX. V-Drive. I ran a 537 prop. Dropped my top end about 2mph like you said. I noticed no real impact on the slalom table. If I were you I would also consider changing your prop to a bit higher pitch to make up the speed on the top end. 

[Slurpee]

By the way, the FAE was a pain to fit into the VLX but I’ll put it at the second best modification I ever did to that boat. LOVED it. 

[Footer613]

1 hour ago, Footer613 said:

Hi all,

I have a 2000 Malibu Response LX ( with manual wedge) with about 650 hours on it.  I am considering adding a Fresh Air Exhaust (FAE) to it to primarily reduce the noise level, since we often slalom and barefoot early in the morning to avoid boat traffic.  Also the Kids surf, so CO reduction would be a good thing.  The concerns are;

1) The boat’s top end is about 44 mph and the FAE may reduce that.  I’ve heard it is about 2 mph.  I prefer to BF at 40 mph, but 42 mph for one footing.  I suspect the FAE may drop the speed into or below that range.  Any thoughts on that. 

2) What is the impact on slalom wake and 90ft back BF wake?  I prefer to slalom at 32 off and 36 off, since those are the sweet spots in the boat’s wake, but interested in any comments on wake changes at all lengths

3)  Are there any modifications I can make to the existing monsoon engine to increase the Hp a bit to compensate for the added FAE drag, …i.e. keep the 44 mph with the FAE?  …ideally solutions that don’t  consume too much extra gas.

 

Regards,

Rob

 

 

40 minutes ago, Slurpee said:

I put an FAE on my ‘01 Sunsetter VLX. V-Drive. I ran a 537 prop. Dropped my top end about 2mph like you said. I noticed no real impact on the slalom table. If I were you I would also consider changing your prop to a bit higher pitch to make up the speed on the top end. 

Funny, I was just looking into that as an option.  Perhaps bumping the prop pitch up 0.5” or 1”, but also getting a better performing prop.  Does anyone have some suggestions?  I suspect it wouldn’t  be a huge loss on the hole shot, but the boat currently has more than enough hole shot for slalom 

Edited December 4, 2022 by Footer613

[Slurpee]

6 minutes ago, Footer613 said:

 

Funny, I was just looking into that as an option.  Perhaps bumping the prop pitch up 0.5” or 1”, but also getting a better performing prop.  Does anyone have some suggestions?  I suspect it wouldn’t  be a huge loss on the hole shot, but the boat currently has more than enough hole shot for slalom 

Call OJ and tell them what you want. They’re awesome about shipping you one prop after another till you find the right one. You’re only out shipping on returns. Acme not so much. But they’ll chat with you on the phone. 

[smileysteve]

To dampen your mood, the sound dampening features apply less as the boat gets higher up (so on waterski plane)

That said, as long as you don't buy the single piece, it's reasonable to adjust the center down spout up and back manually to target avoiding a wake or speed impact.

On my vRide, the exhaust will be in the water creating drag starting in the early 30s, I don't ski 36 off or 34/36 mph very often, but I think you'll see more center spray.

[braindamage]

@UWSkierdid a great write up onan inexpensive option. I followed suit an it has really worked great!!

 

Edited December 4, 2022 by braindamage

[Steve B.]

Seeing the above photo makes me wonder if it's possible to have the exhaust exit straight forward of where it is now, but on the bottom of the hull instead of the transom ? A small primary elbow inside the boat could act as a flapper to keep water from entering the engine... maybe.

Steve B.

[justgary]

The two things I have done that made a significant difference are 1) stainless turn-down tips (bought from a member here who was switching to FAE) and 2) Marine-Torq stainless exhaust manifolds.  The turn down tips don't have the popping noise since they don't have flappers.  The stainless manifolds have much more water damping the exhaust sound, so less noise gets through the engine hood.

[braindamage]

I found @UWSkierthread. His is the same era response as yours.

 

[braindamage]

Also consider that FAE can affect the wake…not sure how badly, but anything sticking in the water will have an effect.

[Slurpee]

19 minutes ago, braindamage said:

Also consider that FAE can affect the wake…not sure how badly, but anything sticking in the water will have an effect.

Potentially. But. Never ever noticed at all. Just a sample of 1 here. 

here’s an ‘01 VLX with an FAE installed. And am improvised surf gate just after they teased us with it, but before it was released. I was so happy it worked so well. But we take it for granted now. 

On turns you definitely here the engine when slaloming or even wakeboarding. But straight line you just hear the board. It’s so nice. And idling through no wake zones at the marina and the neighborhood is bliss. No CO. Or engine farts. 

Dang I miss that boat a lot!

Edited December 5, 2022 by Slurpee

[UWSkier]

which prop is on your boat right now?  I get about 44 MPH with a 525 (13x11.5) with two adult men and about 150 lbs of weights all forward of the engine.  I could get more speed out of it if I'd take out the weight in the front or move it to the back.  Pretty sure the boat ran closer to 47 or 48 with the factory stainless prop, but replacing that was the first mod I made when I got my boat a few years ago.

[Woodski]

@Footer613 - for footing and skiing, I would steer away from disturbing the wake as a noise reduction technique.  The FAE pipe in the water can very well still affect the wake / table farther back at the footing line length along with the speed reduction aspect.  In addition, the added weight will affect the wake, think of it as adding more fuel.  As for the CO effect, a very valid concern for activities right behind the boat.  I keep my boat shut off when people are on the platform or getting on to avoid exhaust breathing.

To add some more noise reduction here are some thoughts:  1. silent rider exhaust, @Michigan boarder can post some pics or look up some of his posts.   2. different exhaust tips (turn down) or MC style with a slip in silencer:   https://www.hardin-marine.com/p-12622-4-slip-in-silencer.aspx    3. ensure your flappers are in good shape or even a bit thicker to deflect water downward.  There are good examples of ski boats that are much quieter than a typical Malibu Response, Nautiques and Master Crafts employ more sound reducing exhaust systems without resorting to FAE, via some of the techniques noted above.

For some more grunt, the SBC (small block chevy) has a plethora of available components to help you.  From a simple 1.6 ratio rocker arm, improved exhaust manifold (see JustGary post), mild camshaft change (GM ZZ4 camshaft), feeding engine with cold air to internal engine components to increase displacement.

[Michigan boarder]

I took my stock 260hp engine to a 390hp stroker, and it's ended up much quieter than stock even with the added power.  Exhaust mods include ETX manifolds, removed the baffles from the silent rider exhaust (but kept the tube shell), 3.5" exhaust all the way back, and SS turn down tips.

[FL33XN275]

I can do an ECU remap and new Stainless steel manifolds to replace the cast iron/alloy 2 piece original/log style manifolds. 

 

with the stainless steel manifolds the increase is between 10-15% with a ECU tune and manifolds 15-20% 

 

[SkiPablo]

Speaking of ETX. My buddy’s 2005 response has been slowing destroying them.  We put a bunch ofJB Weld in the spots that are leaking.  Does anyone know of a cheaper price on these than 1500 each?  Also been tempted to drill/grind them and someone weld new caps on 

Edited December 12, 2022 by SkiPablo

[Woodski]

@SkiPablo - I have noticed the exhaust manifolds have gotten pricier over the years and don't have any help on price.  As for replacement, I would consider alternate materials as my guess is the water (contaminants) running through the manifolds is the corrosion cause.  Stainless steel options may be a better option for longevity, check with @justgary on his manifolds. 

[Woodski]

@FL33XN275 - curious as to what parameters you change when doing a manifold swap?  Fuel map / timing curve changes?  

[FL33XN275]

9 hours ago, Woodski said:

@SkiPablo - I have noticed the exhaust manifolds have gotten pricier over the years and don't have any help on price.  As for replacement, I would consider alternate materials as my guess is the water (contaminants) running through the manifolds is the corrosion cause.  Stainless steel options may be a better option for longevity, check with @justgary on his manifolds. 

MarineTorq make stainless steel manifolds with 10 year warranty. 2 mm 304 grade stainless steel to protect against rust, and has a large zinc anode which protects against electrolysis. 

[FL33XN275]

9 hours ago, Woodski said:

@FL33XN275 - curious as to what parameters you change when doing a manifold swap?  Fuel map / timing curve changes?  

we change all parameters fuel/timing/injectors/air/fuel/boost if the customer has a turbo or supercharged application. MarineTorq's engineer would work with you/dealer to understand what you are wanting to achieve with the boat/tune. 

[FL33XN275]

the manifolds on the engine, are they the cast alloy one piece ETX or long tube style ETX CAT manifolds? have a replacement for both $3168 for a set including GST

[Steve B.]

1 hour ago, FL33XN275 said:

we change all parameters fuel/timing/injectors/air/fuel/boost if the customer has a turbo or supercharged application. MarineTorq's engineer would work with you/dealer to understand what you are wanting to achieve with the boat/tune. 

Don't want to change topic too much. I'm wondering if there are 3rd party computers available that these engines could use with the right software, etc. Work with existing injectors, relays, everything. My guess is gauges would need updated. Just googling quickly now, didn't really find anything other than dedicated ecm's.

Steve B.

[FL33XN275]

35 minutes ago, Steve B. said:

Don't want to change topic too much. I'm wondering if there are 3rd party computers available that these engines could use with the right software, etc. Work with existing injectors, relays, everything. My guess is gauges would need updated. Just googling quickly now, didn't really find anything other than dedicated ecm's.

Steve B.

There are a heap of ECU you could buy, as an example on my boat i use a Holly EFI ECU just depends on what you are wanting to achieve and how much you want to pay.

https://www.holley.com/products/fuel_systems/fuel_injection/hp_efi/hp_ecu/parts/554-113

 

[FSSPCat]

I have the exact same boat and put an FAE on it this year. Noticeably quieter. Didn’t notice any difference in the wake. Still topped out at 44mph. Not that I ever need to go faster than 36mph. 
 

As for noise reduction, probably going to dynamat the doghouse now.