Upgrading Power on 5.7 300hp

[Naf]

I have a 2009 Volvo Penta / Mercruiser SBC with Multi port Fuel injection. It has Vortec heads and Marine L31 Intake manifold.

Stock it suppose to make 300hp, but when i try and pull a skier it bogs in the low rpm. I dont know what the cam is, but i do have hydraulic roller lifters.

I am thinkin of installing Compcam 08-417-8 with 218/224 and roughly .500 lift. I will also use self aligning rockers, ls9 valve springs with the correct ti retainers.

Now given the fact everyone will say anything to sell everything, am i on the right path for more low to mid range power?

I am also thinkin of installin the wet timing belt from compcams pn 5100. This way its less load on the bearings...

I am also controlling the injectors with Dynojets CMD Marine tool and also adding Autotune to keep the AFR in check.

Has anyone else done something similar?

 

[Bondo]

Re: Upgrading Power on 5.7 300hp

I have a 2009 Volvo Penta / Mercruiser SBC with Multi port Fuel injection. It has Vortec heads and Marine L31 Intake manifold.

Stock it suppose to make 300hp, but when i try and pull a skier it bogs in the low rpm. I dont know what the cam is, but i do have hydraulic roller lifters.

I am thinkin of installing Compcam 08-417-8 with 218/224 and roughly .500 lift. I will also use self aligning rockers, ls9 valve springs with the correct ti retainers.

Now given the fact everyone will say anything to sell everything, am i on the right path for more low to mid range power?

I am also thinkin of installin the wet timing belt from compcams pn 5100. This way its less load on the bearings...

I am also controlling the injectors with Dynojets CMD Marine tool and also adding Autotune to keep the AFR in check.

Has anyone else done something similar?

Ayuh,.... Welcome Aboard,... The simple answer is to go to a smaller pitch prop for skiin',...

What rpms ya turnin' at Wot,..??

 

[lg260ss]

Re: Upgrading Power on 5.7 300hp

What kind of boat?
What kind of outdrive? Or is it an inboard?
What is your gear ratio and prop size?
How many people or gear do you have on board?

a 2009 300hp 5.7 installed in a 20-25ft boat properly setup will pull a skier out of the water with no problem

 

[Tail_Gunner]

Re: Upgrading Power on 5.7 300hp

Ayuh,.... Welcome Aboard,... The simple answer is to go to a smaller pitch prop for skiin',...

What rpms ya turnin' at Wot,..??

Im all for the upgrades but as Bondo pointed sounds like a prop...a 5.7 should pull out the arm sockets when propped correctly....22' boat about a 19p prop. So what is your rpm levels with the boat loaded and at wide open throttle...5000?

 

[Naf]

Re: Upgrading Power on 5.7 300hp

I have a 24' Fourwinn

Typically i have 2-4 ppl in the boat, with an 97 quart icebox i slide up front.

Duoprop F6 Props. Originally cam with F5 props but i only got 45mph at 5250, now getting 48-49 at 4750 in

I dont know the gear ratio of the drive.

Basically, i have to give it full throttle, the bow points to the sky, even with the icebox up front. then when i get to about 3200rpm it planes and then screams to 4000rpm. I installed trim tabs to take care of the bow movement, but it only slows the acceleration.

I was hoping if i give the engine the ability to breathe more it will accelerate quicker and the use of Full throttle wouldnt be needed.

I was hoping for a boat i can get over 50mph at wot and still be able to pull a skier out of the water. My last boat did, so i dont see why this boat couldnt do the same...

Could i be too rich at low rpms and that is causing my delay in acceleration? it idles at 13.5afr cruises at about 12.5 afr and drops to 11.5 at wot

 

[aerobat]

Re: Upgrading Power on 5.7 300hp

i cannot comment much on your specific boat / engine but it matches the behaviour of my parents 2010 searay 240 sundancer with a 260 hp mercruiser 5.0 MPI and bravo III drive. the boat is heavy on the back and the engine has to work hard to push it on plane - and the bow skyrockets initially.

gunning it out of trolling speeds the 5.0 does not act much more powerful than my 3.0 Volvo in a 21foot cabincruiser (and thats a lot of boat to ask a 3.0 for ) , simply because my boat lifts up the back much more easily. when on plane the 5.0 MPI leaves my 3.0 of course.

it would be interesting if somebody has deep knowledge on the engine mapping - is the engine somewhere castrated to meet californian emission standarts ? i have to agree i would expect a little bit more punch from a multiport injected vortec V8.

 

[Walt T]

Re: Upgrading Power on 5.7 300hp

Something isn't right. He should be leaping on plane with the F5 props and that engine. F4s are not appropriate for that. How about gear ratio? Has the boat ever performed right? What 24' Four Winns? Deckboat? Horizon? Signature? Vista? Answer our questions and we will help.

That motor is plenty for that. I driven many Four Winns with 5.7s and they all were fine. Vista cruiser, well ok its a little slow.

Do NOT modify a fuel injected motor. The ECM is not programmed for that. Trust me, I've seen engines guys have tried the old school mods on these motors. It will end badly and expensively.

 

[MikDee]

Re: Upgrading Power on 5.7 300hp

If it wasn't a duo-prop setup, I'd say look into venting the prop, but that may not be practical? If you're basically looking for a better hole shot, try a Doel fin. This will have a tendency to lift the transom on take off, hence leveling the boat, & taking a load off the motor. You might even get more top speed. Ya got nothing to lose, but a few bucks.

 

[Tail_Gunner]

Re: Upgrading Power on 5.7 300hp

I have a 2009 Volvo Penta / Mercruiser SBC with Multi port Fuel injection. It has Vortec heads and Marine L31 Intake manifold.

Stock it suppose to make 300hp, but when i try and pull a skier it bogs in the low rpm. I dont know what the cam is, but i do have hydraulic roller lifters.

I am thinkin of installing Compcam 08-417-8 with 218/224 and roughly .500 lift. I will also use self aligning rockers, ls9 valve springs with the correct ti retainers.

Now given the fact everyone will say anything to sell everything, am i on the right path for more low to mid range power?

I am also thinkin of installin the wet timing belt from compcams pn 5100. This way its less load on the bearings...

I am also controlling the injectors with Dynojets CMD Marine tool and also adding Autotune to keep the AFR in check.

Has anyone else done something similar?

Ahh missed the dynojet part i was very intrested in that product but stood down when i tried to implement the o2 sensor. If you have a dry exhaust it should work if your running a wet system i cannot see how it could work. One big issue would getting the sensor to the appropriate operating tempature and then surviving in that wet enviroment..Id pull it and see what happen's

 

[Maclin]

Re: Upgrading Power on 5.7 300hp

How did it behave with the F5's when pulling up a skiier?

 

[Walt T]

Re: Upgrading Power on 5.7 300hp

I got a chance to play with a Dynojet, I suppose on a car it would make a difference but not on a boat. Its just a few HP up or down. You must have a O2 sensor for it to know how to manage fuel and even then it cant be accurate without a dry O2 sensor on both banks. One isn't good enough so you have to buy the two sensor package. I dunno about wet exhaust, I don't see how it can work. As I said, there is so little benefit power wise. It just goes to show how well the original ECM is programmed.

 

[Tail_Gunner]

Re: Upgrading Power on 5.7 300hp

Actually what very well may be happening is the engine is in a lean burn situation causing knocking under launch in return the knock sensor's would retard the timing and dumbing down the whole system. You would not be able to hear the knocking the sensors pick it up far in advance to audilbe knocking.

 

[Walt T]

Re: Upgrading Power on 5.7 300hp

Good point Tailchaser

 

[Scott Danforth]

Re: Upgrading Power on 5.7 300hp

Im leaning toward two things - wrong prop for water sports and a retarded ignition

the OP put higher pitch props for a top end and now is complaining of the lack of low end. duh. :facepalm: put the F5 props back on for skiing and the F6 props on for high speed runs. this is a case where you have only one gear and your trying to do everything. Not going to happen. if you want to go fast on the top end, you sacrifice the low end. if you want the low end, you sacrifice the top end. the only way to fix this is with a 2-speed outdrive. Yes, there is a company that makes one for volvo penta legs. on my DP290 I have a set of B5's for water sports and B6's for top end. will soon be running B7's However to get the boat to pop out of the hole when full of beverages and people and skiis, etc, I need the B5's. Takes way too long with the B6's

Also, as Tail_Gunner pointed out, if your getting a lean ping, the ignition will be retarding making the motor fall on its face. a bit of water in the fuel will cause a lean sneeze which will be caught as a ping and the ignition will be retarded.

I am also all about mods. Changing a cam is a great power adder. However you will need to re-program the ECM to take advantage of it. Regarding the wet timing belt. Not sure its worth the $400 to have a wet timing belt over a $50 double roller timing chain. heck, for that cost I would go with a cheater gear set. Again, not going to improve anything over a $50 double roller timing chain.

 

[Naf]

Re: Upgrading Power on 5.7 300hp

With the original props it acted about the same. I havent played with anything. It came with side exhaust ports that i use so i can spin the props quicker but same problem. Points the bow straight up then starts to plane.

I asked compcams about the timing belt but they said it was for serious racers. I see a benefit of more accurate timing And no stretch for about 100hrs which for me will be about 2-3 yrs

I am gonna ask my friends about changin the cam and rockers. That may help me spin the props quicker and not shoot for the stars.

There use to be a dolphin for my drive but the company has stopped makin them. I have the fins but no bracket to attach to my drive unit

 

[Walt T]

Re: Upgrading Power on 5.7 300hp

Timing chain will NOT help this nor will cam and rockers. You will simply be wasting money. Get it out of your head. Once again, what boat are you talking about? 24' Four Winns what? We try to help but some folks already have it in their head what they want to do. It's your boat, your money, your sweat, have at it let us know. Hopefully I'm wrong.

Given the performance numbers, I'd say the F5s are right. F6s get you to nearly 50 mph so obviously there's power. The RPMs are perfect. If you change cams you will make the low end acceleration worse, not better. Yes your car guy friends say it adds power, it does but at the TOP END. If you try an "RV" cam there will be absolutely no difference since your current cam profile is similar. Timing belt could get you 5 hp max. As you said, it's for serious racers grasping for every available HP. If you go for higher lift and change rockers, make sure your Vortec heads are compatible. DO NOT go over .490 lift without modifying those heads. You will damage them and your wallet. Be aware of duration, long lopey cams will bring water into the cylinders and bye bye motor. Lopey cams may not even get your boat on plane. Automotive HP improvements are much more noticeable because a car doesn't have to push an enormous wall of water out of the way. Forget auto performance mods. That's the wrong tree you're pissing on. Your friends mean well, I'm sure they know what they're doing. You are trying to learn. I'm calling it like I see it. We are trying to help, and hopefully keep your money in your pocket and only spend it on what will really work. If I have to get a little riled up and make you mad well then so be it.
Just to be clear, Everything you have mentioned will not get you what you want. We've all been there. Aint no dummies here. Well ok maybe one who shall remain nameless but his name starts with a W.
You say you installed trim tabs and made it worse. That can't be right. With drive trimmed all the way down and tabs properly installed that will do wonders for this blue sky pointing. Something else is wrong and your motor is fine. It's time to stop, regroup, and look at it again from a different perspective.

 

[JustJason]

Re: Upgrading Power on 5.7 300hp

You need to get rid of the CMD thing and go back to stock ECM fuel/air curves. I don't know if you have a Mercruiser or a Volvo. (you said you somehow had both , but you appear to have a Volvo drive).
None of those aftermarket fuel/air controllers work worth a squat. I can guarantee that Mercruiser as a whole has way more engineering experience than this dynojet company does. And Volvo has 100x more experience than Mercruiser.

As to this;

Could i be too rich at low rpms and that is causing my delay in acceleration? it idles at 13.5afr cruises at about 12.5 afr and drops to 11.5 at wot

A rich engine will bog when punched, and almost always followed by a little bit of black smoke out of the exhaust. A lean engine will sneeze in the intake. But in the real world, in marine engines, these engines are full load engines. And because of that they need to run rich. They need to just rich enough that your not bogging. Your on the lean side of stoich, when you should be on the rich side. You should be 15 to 16 to 1, in that area. With the ratios your running, your going to burning up your valves. (if you have not already, I don't know how long you have been running it like this for).

What I would do is get rid of the aftermarket stuff, put everything back to stock, and re-run the boat.

 

[lg260ss]

Re: Upgrading Power on 5.7 300hp

I think you are dealing with some user error. You say that the bow points to the sky, well I once owned a 24' fourwinns horizon with that same engine and never had an issue planning. Are you sure your drive is down all the way? Have you tried lowering your trim tabs, you shouldn't have to but it would help.
When you say it bogs down in low rpm, maybe you need to be a little easier on the throttle. If you go from idle to full power too quickly the engine will bog down for a second. Try starting your hole shot just above idle, between 800 and 1000 rpms and use a smooth motion, don't just gun it.
I agree with some of the previous posts that you will just be throwing money away modding the engine.

 

[Naf]

Re: Upgrading Power on 5.7 300hp

I have a horizon edition.

If i drop my tim tabs all the way down then yes the boat remains level, but the acceleration time is increased as well, more drag to overcome.

I havent changed anything yet, i used Compcams to find the Marine cam. They have three, mild good and wild. I took the good cam for lift is only 0.500. I am well aware of the coil bind and will upgrade the valve springs to LS9 with Ti retainers. They are good till 0.55 lift and the seat pressure isnt too high.

I will stay with the stock cam timing chain.

I understand the engine is at high loads all the time, but you all have to remember, to much fuel is just as bad as too little. I am running 95 octane fuel and i change the oil, plugs and filters at the beginnin of every season. I barely put on 20hrs a season, and i use synthetic oil and KN oil filter.

I chose the 218/224 for the cam mimiced the LS7 cam. That cam had great bottom end torque, but i think it was because of the wide lsa. We have narrow LSA. i need an LSA, Lobe seperation angle, greater than 115, then i will make more bottom end torque.

 

[JustJason]

Re: Upgrading Power on 5.7 300hp

I understand the engine is at high loads all the time, but you all have to remember, to much fuel is just as bad as too little.

That is where you are incorrect.

But.... Your the one playing engineer here. Like everything else, you will either figure it out... or you won't.

On another note, if your pulling up a full size adult, and your using a bridle attached to the D rings on the transom, that is going to pull the bow of the boat up in the air. Until the skier is up on plane, it's about the same as dragging a 1000lb weight. Make sure you start full trim in.