davids94

Hey Guys,
Im thinking about some new additions to my 5.0L Fi Volvo Penta(ford 302). I've been told by some that keeping the engine as close to stock is my best bet for reliability. I understand where these guys are coming from but could changing the setup drastically affect dependability? The changes Im thinking about making are pretty generic when it comes to cars but I don't know whether they make sense on my boat. They include:

Boring the cylinders
Shaving the heads
Adding a roller cam and lifters
Increasing the cam size
Adding roller rockers

Will any of these changes cause issues? In addition is there anything else I can do that will give me a few HP safely? Thanks for all your help in advance!

mcollinstn

Boring the cylinders won't do squat for performance unless you have scored cylinders to start with. You can rpelace with high compression pistons for better performance, but you can do that with your stock bore..

Shaving the heads will raise compression. You may see some benefit there, but usually increased compression goes hand in hand with a cam change.

You neglected to tell us the year of the motor, but you probably ALREADY HAVE a roller cam. A DIFFERENT roller cam should allow some gains.

roller rockers are usually not going to make a world of difference on a dyno. They are usually dropped in when a high lift cam renders the stock stamped rockers either unable to move far enough without binding, or flexibility concerns arise with stiff valvesprings.

Be aware that any significant modification will probably require reprogramming of your FI computer. In some cases, an aftermarket pressure regulator can "be good enough" for the increased WOT fuel flow you will need, but at the expense of idle quality and low speed mix.

With that said, a 5.0 ford has WORLDS of inexpensive and effective modifications available.

A cam matched to a pair of performance heads will net you the biggest gains.
If your boat is heavy, you may benefit from a 347 stroker kit.

davids94

Its A 1996

Sean H

that motor can make 350HP all day without any trouble, get a cam/head package that works together, go roller on everything, i probably would even look for a gt-40 intake set.... probably some more die hard 5.0 guys on here, i haven't messed with them for almost 10 years now..

davids94

I've been told that increasing the compression on inboards is not a good idea. Is this true? In addition I think the same gent told me that if I got a new cam it might allow water into the cylinders. I don't know that much about all this (obviously) so all and any advice is welcome.

In addition, The engine was rated at 220 HP by the manufacturer. Im almost sure that when this same engine was put into the mustang it produced 270. Do you really think with the upgrades (but without a supercharger/procharger) I can get 350HP?

mcollinstn

The '95 5.0 Mustang made 215 SAE net hp. That's pretty much the base for your marine motor. The '96 Stang used an all-new modular "Romeo" SOHC 4.6, also at 215hp.

Hot street cams with a lot of overlap will cause water reversion issues in a boat with wet exhausts. You can still get a much hotter cam than your stocker without much trouble. After market heads (TFS, Edelbrock) will really wake it up.

I'm not familiar with the EFI setup on your boat. It may or may not be genetically related to the auto stang motor. 350hp is indeed attainable, although you'll have to carefully match the cam with your exhausts. Stock exhaust manifolds will not tolerate a wild cam. Also, being a smallish (302ci) motor, big hp will come at the expense of low end torque. Depending on your boat's size and weight, these may not be good trade-offs.

bglz42

I've been working on my Ford 351W in my 1970 Donzi, blew a head gasket. In researchng these Ford small blocks I found TONS of good info about them. Lots of heads, cams etc available. Lots of efi stuff. Most major cam companies sell marine cams for Fords. Just match everything, and you'll be good.

deboatmon

As Sean H stated, that motor can make 350 horsepower all day long. Well, that might be pushing it a bit actually. But at what RPM can it make that much power. I really don't see making those mods to a very small marine motor. It will have to rev high to get anything and that may not be a great design for most marine applications unless you're racing. A light, easy planing, fast hull might be pretty nice with that combo. But, if you're a middle of the road lake boat, hauling 4-5 persons, turning 4000+ RPM to cruise might not be what you're after. The bigger power most likely won't enable much of a larger prop because of the HP/torque curve. You will have to utilize the HP with higher RPM. I've built and owned several hopped up 327 Chevies and they were great. That is in my 1966 Chevy II w/4.88 gears. To make more power, you'll have to turn it faster. With a 302, lots faster. The torque and HP curve will go up substantially along with the valvetrain mods. A 351 would be a better choice in my opinion and would offer lower cruise RPM and more low end torque as well. After all the mods you would have to make, the costs might be similar. One main difference would be that one idles hot and requires 93 and the other idles smoothly and runs all day on 87. And, the stock, lower cam profile would offer greatly extended valvetrain maintenance intervals and little chance of water reversion problems with stock exhaust.

Just my .02.

Good luck, whichever way you go. Either way will be lot's of fun.

cstraub

Your best bet would be a stroker kit to make the engine 331 CID. the 331 kit adds a .250" more stroke to the crank for the added cubes. If you want to go heads I would look at the Roush/World Windsor Jrs. These are by far the best bang for the buck and will give you some excellent power for the money. The stock hyd roller in these engines is a good cam. I would just add 1.7 rockers to the block and reuse the camshaft. You may want to change the lifters if they have some time on them. These mods will net you an easy 300 to 320 reliable HP that will idle like the original.

Chris

davids94

Thanks for all the great advice.

My boat is a Four Winns U-19 Unlimited (essentially a donzi hull) It weighs around 2400lbs (hull motor & outdrive) I believe the hull alone wieghs in right around 1000lbs.


Would it be a better idea to leave the engine stock and bolt on a supercharger? As opposed to modifying the existing one?