Ideas for increasing power in a pair of Merc 454 L29s
 

Just to be up front about this, I'm just toying with the idea of how much it would cost and what would be the best increase for the money/work required.

The boat:
'99 Formula 330 SS
Dual Merc 454 L29 engines (SN: 0L34xxxx) w/ about 400hrs/ea (stock AFAIK)
Bravo 3 outdrives, rebuilt by the previous owner two years ago (at the insane cost of $14k!!!)
26P props

What I've done so far or is in the works (all done after winterizing):

• New NGK BPR6EFS spark plugs, the old ones were Champion RS12PYP and look WELL past their service life.
• New MSD ignition wires
• New fuel filters
• New Sierra distributors and caps
• New K&N Air Filters/Flame arrestors (don't worry, I don't expect miracles from these)
• fuel/water separators changed
• Oil/filers changed
• Drive fluid changed
• All ethanol fuel should be out by now, replaced with ethanol free
• Replaced a thermostat including the gasket that was totally missing!

As of last year I could get to maybe 46-48mph on a smooth day, but, well, I like SPEED! I was hoping I could get it to 60mph+ safely, but I don't actually have a target speed. Currently the holeshot is VERY good (in my very limited experience) unless I have it seriously loaded down with people and gear. I haven't yet seen how much of an increase the work listed above will get me, I don't expect much...

So now with Spring finally hitting us in the DC/VA/MD area, I'm getting curious about some REAL upgrades I could do, here are a few of the things I've looked into: (listed by level of sanity)

• Bottom paint (needs to be done soon regardless)
• New props
• New intake manifolds
• New exhaust headers or more?
• New MSD ignition system.
• New heads
• New cams
• New forged (mine are cast) cranks/pistons/arms
• New complete engines
• Superchargers (quickly realized how bad of an idea this would be on my old engines and the price)

Is there anything I haven't considered? Which of these would be the most nag for the buck? Every time I look at prices I remember that I have two engines, so the price and work doubles...

Bottom paint will scrub speed . Two 500 to 600 hp engines and bravo I's would make you smile . Only question is , is doing this to the boat you have worth it to you ? It's a waste of time to try and soup up those 330's unless you want to invest lots o money . A simple tune up will gain you nothing in speed . Little tweaks that you can feel in a car do nothing for a boat .

Short of bigger motors with a lot more HP, there is nothing you are going to do to realize any significant gain in speed with your current setup. If you like speed, you need a different boat. With that said:

Bottom paint - costing you some speed. If you can get a lift or trailer the boat, remove the bottom paint.

Weight - gear that is rarely used or not needed adds up quick. Lighten the boat as much as you can.

Props - make sure you are hitting 4,600 RPM at WOT. Brett at BBlades can lab your propsets for a little extra speed but you will most likely give up cruise efficiency.

Exhaust manifolds - if you boat in salt or brackish water and the manifolds need replaced, you might consider Stainless Marine or other aftermarket aluminum manifolds. You might realize some slight gains due to the reduction in weight and slightly better breathing. Headers would be a waste of money on those motors.

Do note that some K&N marine filters are more restrictive than the flame arrestors they replace.

Hmmm, I really like the 330 SS, so I'll probably just make sure that it's running at it's peak and be done with it. I based most of what I said on hearing others say they can get their 330SS to ~55mph, although I take anything like that with a huge grain of salt.

I was told when I bought the boat last year that the bottom paint was on it's last leg, I planned to do that very soon. Unfortunately I can't trailer the boat though, I have no lift at my marina and no trailer or truck (that's big enough). I assume you meant remove the bottom paint and reapply it?

Very good point about weight, I think I'll be taking a lot of stuff out of it very soon... I'm also probably dragging around a lot more water than I should, since it only gets used for the toilet.

My understanding was that I should be getting 4800 WOT, which I'm getting on one engine while the other seems to hit a wall at like 4200. That was before I replaced the thermostat seal on that engine though, which was preventing it from getting to the correct temperature. Before I started investigating this further I wanted to rule out all preventive maintenance problems. The props were checked during the survey last year and I was told they were in very good shape. The seller claimed they were replaced the year before when the outdrives were rebuilt.

Nope, she stays 100% in fresh water. I've looked at exhaust before but I wasn't sure how much it would help...

I did some very simple breathing test for the flame arrestors where I held them to my face and tried to breathe, the K&N clearly let through substantially more air, but the stock filter looked NASTY!

What about the intake manifold? I've had a few people tell me that they made a significant difference on these engines.

Thanks for the reply,
Dan

You would be better off upgrading to 496 HO's. 425HP or even a 502 Mag EFI 415HP. Will give you some added pop without breaking the bank. Would definately put you in the mid to upper 50's.

Like the deep said, your not Going to feel anything with mild mods to those motors only effective route would be two healty 450 ish Hp motors...or get a faster hull...?

If one motor is turning 4800 and the other only 4200,you do realize a strong one will kind of drag a weak one along .Are you sure drives are same ratio?. Same props ? . Tachs right? if they are, start figuring out what is wrong with 4200rpm motor. Fuel pressure? bad hole? You may just need what you have to run right to get 50'ish.Just food for thought

the one thing to try if you can bum a pair is installing Bravo 1 lowers. of course the hole shot suffers a little but a B3 is built for comfort...and then you have prop options...

In op's second post he states one motor turns 4800 and the other hits a wall at 4200.Shouldn't we make sure we have two healthy soldiers , before we start spending money on more motors, drives..etc.

I agree. And for the most part, I wouldn't recommend modifying the 7.4L L29 MPI engine. In stock form, they last a long time, and run great. Not big power, but they are nice mild user friendly engines.

If you wanna go faster, I'd sell the engines you have in stock form, and replace with either 496HO's, 502 Mag MPI's, or something like that. As for the Holeshots, go easy, bravo drives don't like to be hammered on out of the gate. Good luck.

But, before anything, I'd find out why the one engine is down 600RPM. It could be either a engine issue, prop issue, or hopefully, when they rebuilt the drives, they didn't install a different ratio gearset in one drive. .

To the OP. I kind of went through the same steps as you after having my boat. Did some of things you did, but in reality those are all good maint type things that will only help your engines live longer. I really had to go through a cost effective approach to it and what I needed. Really came to the conclusion getting a different boat was the best option. But I ended up stick with that what have, I rarely go the top speed anyways, and having those bigger engines opens me up to a whole new world of performance boating and spending money.

Thanks for all the replies, I agree with you guys that I can't do much within reason to increase power. With that said, I have some new info to add...

I took the boat out last Wednesday and again yesterday, the water yesterday was absolutely amazing and I figured it would be great for testing where I currently stand...

My results: at WOT I hit 46mph, but at only 4100RPM. Both engines read exactly the same RPM so I doubt it's a tach problem (the tachs are brand new too, just replaced last year). The strange thing is I hit 4100RPM a fair bit before I am at WOT, but the last few inches of throttle don't seem to be doing anything, so I doubt it's a cable problem (as I previously suspected).

I don't know the outdrive ratio but the Props are 26p. I know the outdrives were rebuilt two years ago by the previous owner so the gearing may have been changed at that point. Since this is my first and only boat I don't really know if my holeshot is as quick as I think it is, but I seem to get up on a plane extremely quickly.

If you were under propped you'd hit the rev limiter, instead you're about 20% short. A pair of 24's may help.

Dan, any change in wide open rpm when adjusting trim up?

out of curiosity, did or can you do compression test. might hook vacuum guage and timing light to be sure they are good. want to make sure engine's sound prior to spending time when somethings not right.

I have not, but I doubt this is the issue since both engines are hitting the EXACT same RPM and have the same oil pressure (40PSI) and temperature (180° F) while on the water. I highly doubt they would both be having the same exact compression issues.

It didn't seem to, but I didn't raise it very high, I never seem to need to... unless my understanding of how I'm supposed to be handling trim... I thought the goal was to keep it as far down as possible unless I'm having trouble getting on a plane. Is there a comprehensive guide somewhere on how to handle outdrive trim?

A lot of rpm and mph can be had in proper trim and tab settings. Assuming everything else is mechanically sound this may be your problem.

Update: assuming the drives didn't get changed during the rebuild, they should both be 2:1 drive ratio.

Also, a seemingly dumb question, but since I don't bring the boat out of the water I don't know... For the trim tabs, when I press up on the switches should it move the tabs up or the bow up? I need to figure out how to fully retract them.

You needed a compression check, sounds like the motors are not performing nearly as efficient as possible, I have twin 454s on my 31 sonic and hit high 60s low 70s, I had heads machined and valves redone and was a huge difference, get a trusted boat mechanic to take that baby for a spin. If you can't get anymore speed out off that boat, then sell it don't sink drastic measures in a lemon, chicken salad/chicken ****

Do I have a costly story for you.
My wife and I purchased a 2000 330SS in 2004 with the 7.4 efi engines. After a few years I felt I should go faster. Part of the problem is I feel the walk through windshield is safer for my wife that doesn't want to swim. This is another story. We want a walk through transom. In other words the layout is as good as I can find for the money.

When we purchased the boat there was a pair of bravo 1 drives available that I purchased and had installed. On the best day the boat wend about 51 mph.

The next thing is we rebuilt the 454's into 489's. This brought the boat to about 58 mph. This proved to be less expensive than 525's however nowhere near as mush power.

I had the 22 pitch props lab finished. This brought the boat up to about 58 on the GPS. I know but when the drives are lifted they no longer start cavitating.

The next thing was the above water exhaust. This gave us another 25 rpm or almost 59. Sound great.

I ground off some of the 3/8" hook on the bottom. This got us to about 59.5

I have installed CMI heders last year. Still not 60.

I talked to some other comrades and I am thinking about shorter drives. One recommended drive extensions.

You can really spend money if you try just a little bit.

On Formulas, up is tabs up, not bow up. Put tabs down for planing and start bringing them up once you get up to speed. If you have been reading them as bow up instead of tabs up, then you will be shocked what happens when you get the tabs to level or just above.