David Haag

I just purchased a 97 hammer with the 310hp 454. Its stock and I want to know where to start with the mods. I am new to marine engines so I know basically nothing. Dave Haag

Madmax

Fuel injected or carbed? If it's fuel injected, lab the prop, and leave it alone. If it's carbed, we can go to work....

Caincando1

I believe a 97 should be carbed. There are a ton of thread on engine mods for this engine. Do a search and see what you come up with.

Brian

SledgeHammer

I have a 2001 that was a 310 with fuel injection. I pulled the engine and sold it and put in a 468 with Merlin heads, Crane 731 cam(because I have captain call exhaust), 750 Holley on a Dart intake, and roller rockers. Changed prop to a labbed 25 Mirage plus. Speedo went from 70 to what would be about 84 -85 if the markings went that high. The GPS is 77.8 on a hot day with two aboard and 3/4 tank of gas. The speedo in these things are way optimistic. The boat came alive. I did put add on hydraulic steering which helped considerably, but it would be better if I went to the full system. I am considering going to a shorter lower unit for more speed and better handling.

David Haag

I have the 454 with the carb. I think they have a 454mag with fuel inj. I would like to add around 100hp.

Pat McPherson

Well it's getting cold out (not as cold as where Max & Cain are from, but...) so talking about our off season mods to our boats will have to do...

I have a 1999 310HP/7.4MPI which I believe is the same L-29 base engine as yours. I have been told by engine builders that have modified them that about 375HP is about the best you can expect from the GM fuel injection system. I am going to make some changes and we'll see how it goes. If I'm not satisfied then the MPI will come off and a carb will go on.

My plan:
The heads have been bowel ported and new stainless valves installed with a set off double springs to match a hotter cam that I have not yet purchased.
As for the new cam: it will likely be a Lunati 218/226, .534/.544, 112LSA. If you plan to upgrade your exhaust to something with a longer than stock riser, the ZZ502 cam with matching springs, is the most cost effective up grade.
The exhaust system I will be using: Stainless Marine aluminum manifolds with short stainless risers for captains call.
The fuel injection goes back on with a reprogrammed ECU from Arizona Speed and Marine. AZS&M has told me that they are vary familiar with the L-29 and can remap the ECU for my upgrades... We shall see

If you have a carb engine, you can skip the $300 MPI experiment and just buy a new Holley double pumper...

Good Luck!

Pat McPherson

I was writing my reply when you came back that you have a carb engine.

Anyway, Madmax has experience modifing this engine and will give you good advise.

Another 100HP may be beyond the safe limits of the L-29 base engine as it has a cast crank, cast pistons, and small rods. I have been told by a number of people to keep the max RPM below 5000...

If you would like to tinker though, there are many things to make more HP. Just depends on you budget...
New cam, intake, carb and exhaust can give big gains.

David Haag

After searching and reading alot of posts, I think the whipple s/c is the best bet. What do you think about the s/c madmax?

excalibur al

not much you can do with a 7.4 best thing you can do is sell it . and put a 496 in it.i just did it to mine .

Madmax

I'm not sure of the installed height of a whipple. I had a hammer, and when I checked into installing a regular supercharger, it was 8 inches from the deck to the top of the supercharger, and then add a carb and spark arrestor on top of that. Mine was about 3 inches 2 short with the hatch closed. If you have the larger oval port vortec heads, you cannot install a whipple on them anyway, they are VERY detonation-prone.

There are some cost-effective mods that can be made, but sometimes ya hafta ask yourself if you are going to own this boat for any duration. There are some very fast Hammers on this board, but they are (at least mine was and the 1 other I have ridden in) a chine walking nightmare above 70mph. Hydraulic steering and real tabs (not the cheesy pieces of tin they put on them) are needed. Any mods on a smaller boat like this you can pretty much count on not getting any $$ back at sales time. Talk to most dealers, and they will tell you most of them take add-on superchargers OFF boats before they sell them because they are a dead horse with them on. I had a blast with mine, and sold it after 2 years for way more than I payed for it and upgraded to a bigger boat. A 25 outlaw or 272 is a very nice step up that can take some power mods.

If you wanna go ahead with it, just tell me to shuttup, and i'll give ya what I've done to my latest that had a 310hp. Picked up some good horsepower!