454 Mag/Carb upgrades

[Dooger]

I would like any advice as to some smart upgrades to make in the near future. I just purchased a 1997 261 26" Checkmate Persuader with 286 original hours. The boat is in mint condition with a 454 Mag/Carb with I was told 365 hp matched to a Bravo One. The only change now is the Corsa quick and quiet exhaust. The exhaust is not select choice/silent choice just straight thru-hall.

I'm considering on some upgrades to pick up some performance and speed. I'm thinking of updating the manifolds/headers, maybe E.M.I or Stainless Marine manifolds & risers due to the cost and reading like they are a good product? I know CMI makes a great header but they are so expensive. After finding the right exhaust, I'm thinking of porting/polishing the heads with upgrading the hardware and rockers with a nice matching cam shaft. Are the heads worth opening up or should I consider new aftermarket heads? I was reading that Dart and Edelbrock make a nice flowing head for the 454 but I'm trying to keep the cost down. Then on the top end matching a good flowing intake manifold and carb set up. From there I was told I could probably pick up 80-100 hp pretty easily. What are your thoughts on this setup or motor and do you have a bolt on package with these components that can be matched up to perform the best for my boat/motor.

Thanks for any help,
Doug

 

[boatn70]

its my understanding the best mods are intake carb and cam change. some here may be able to tell some more details. the heads arent that bad, the intake and carb usually stink, check around all the boat sites and do some searches, your bound to find a ton of info.

 

[vinny p.]

Hello Doug,

Welcome to the board. I can definetely help you out with this.

I am not sure of what cylinder heads your engine currently has. If they are oval port, I would say dont spend any money on them. If they are rectangular port, you have something to work with. You are heading in the right direction with your thoughts. If you do anything, you must match all your components. Cam, lifters, springs, retainers, keepers, rockers, intake, carb, exhaust, heads or head work. The choice of either aftermarket heads or doing some port work is simply $$$. Aftermarket heads would be the better choice. One problem to consider is whether you run in salt or fresh water. If salt, you have to worry about rotting out any aluminum components you get. Closed cooling is highly recommended. Exhuast is your next biggest expense. I would recommend CMI's. If not within your budget, look at something that has a water bypass between the manifold and riser, like Gils. They eliminate the problem of a gasket being the only thing keeping your engine alive. Cams-- definetely choose a hydraulic roller, stay away from flat tappets. They are old technology that should be buried with your old rotory phone. Be careful of your valve overlap. Ask your exhaust manufacturer what their exhaust system can withstand without reverting water. They may not even want to tell you. If they dont, ask others what they are getting away with. Keep the lobe seperation at 114* , that will knock down some of the reversion. Holley or Demon carbs are the same in my book. Just make sure you use a marine version. You will have to upgrade your fuel system as well. The stock pump and small lines may not keep up with the engines demands. Better off having more fuel supplied than less.
Dont forget to add into the budget for a new prop. You will need a good Bravo 1 4 blade, maybe a labbed 26" or so.
Keep your upgrades to a reasonable level so you can safely and reliably enjoy your boat. By this I mean, dont build a bigger powered engine than your hull can safely handle. Or you will find you need hydraulic steering, tabs and an XR drive to keep it running.
The problem with doing this, is the cost of the incidentals that kill you. You can budget for the big parts, but then all the small ones come out of hiding when you least expect it.
I just upgraded to T&D shaft rockers. I have a complete set ot Comp Cams Pro-Magnum 1.7 rockers, with ARP nuts and AFR studs with guide plates, I was going to put on E-Bay. I also have a labbed 26" B-1 that may work for you. If interested, I can cut you a deal on them.

 

[cdaallison]

454 upgrade

I had a 454 mag ( 365 hp) in a 23 velocity that I too wanted to bump the horsepower. I had Jomar engineering flow the heads and put in new offshore valves ,we put in new forged pistons (bumped comp up to 9 to 1),roller rockers , high rise intake manifold , 850 holley carb, K&N aircleaner, stainless marine exhaust manifolds and pipes and put in a 10 quart oil pan and aftermarket oil cooler. The results were less than spectacular. I gained about 4 mph (68 to 72) if perfect conditions 73 gps. A friend with the exact same boat bolted on a weind super charger and a bigger carb and was 1 to 2 miles an hour faster with way more low to mid range power. He didn't put exhaust or anything else and motor has been very reliable last 10 years.I thought based on Jomars claims that I would have been faster. If I would do it again I would have bought a low boost blower and added exhaust and a intercooler later (with an increase in boost) and had a 80 + mile per hour boat like I wanted. I ended up selling my Velocity and buying an Allison Grandsport with a 225 promax (93 gps and 1/2 the fuel use) Allisons ROCK!!! Put a blower on...Just my 2 cents, for what its worth. Mike

 

[Dooger]

Vinny,

Thanks for all the great advise, sounds like were both on the same page. I'm trying to be smart about the upgrades for sure. I don't have $10,000 to put in my motor and don't want a big motor or certain parts like you stated, the smaller ones will come out. Come out they will, broken. It's like building a car, I wouldn't build a 600 hp motor with stock trans and rear end as well as chassis. I just want to bump up my power to have it on hand if needed. I run on Lake St. Clair in Michigan and some of my buddy's have some nice go fast boats I know I won't beat them but just sick of being way behind in the pack. They run a 33' Powerplay with twin 502's and just pulled them to build to 650 hp apiece, as well a a buddy from Flat Rock that runs a 32' Active Thunder with twin 540's 750 hp each. I feel like I have the dinggy of the group but hey it works good for me.

I maybe interested in those extra parts you have. I have been talking to CP Performance Marine and they have some real nice combo parts. They have a matching Hardin Marine Manifold/800 Holly Carb set up, matching Cam. This is the 500HP set up they advertise. This is what they recommended:

Doug,
The Dana Manifolds are $1375.00 with the aluminum risers and $2040.00 with stainless risers. We also have Gil's with a stainless riser at $2199.00 for the set part number 420-901030pol. The cam kit I'd use is part 295-011008K at $1190.00 for a gen 6 or 295-011008K at $999.00 for a gen 4 engine. We also offer an intake and carb package part 620-54000 at $790.00. (this is on sale through Dec for $725 right now)
I think that 80 to 100 horsepower from these parts is alot to ask 50 to 75 would be more realistic. If your heads are in good shape go ahead and use them

 

[vinny p.]

At least CP was honest about their intended hp increase. If you can, get more specific information, especially the cam profile. Is the price he quoted for a hydraulic roller. I dont think it would be since the kit includes springs. I would say go for the extra few $$ and get the Gil manifolds. They are a much better piece.
If the heads are original with nearly 300 hours on them, I would pull them off and have the angles cut. Installing bronze guides and inconel valves would be a plus as well. At your target hp, the inconel valves are not imperative, but bronze guides should be high on your list

 

[Old Navy]

Good exhaust if you don't already have it. Then add a Weiand 177 at moderate boost. Good bang for the buck. You don't have to re-invent the wheel here. There are a million other options that will work, just depends what you are wanting to do. Be aware though, BOOST IS ADDICTIVE! You will always want more..........

 

[Dooger]

Vinny,

What are your thoughts on building my boat as far as a 1997 26' Checkmate goes thinking of it more over the weekend. I was talking to a buddy of mine that has a 33' powerplay that he's building. He knows a buddy that has a used set of CMI headers and tail pipes that would fit great on my boat and should be able to get a good deal. He was stating that depending on what Money and movements I want to make in the future I may want to just open up the exhaust and stick with that. He stated that if I start building the motor and get above 70 mph I should probably think about Hydraulic Steering, Also if I build the motor will the rest of the boat handle it. The more I thought about it I'm not sure if it's smarter to open the exhaust and save my money for something bigger down the road or build the boat and run with it. I plan on keeping the boat for a few more years for sure. I just picked it up last July and had a blast with it. But I don't have $10,000 to put into it if I'm going to build the motor and then have to build/strengthen the rest of the boat as well.

Just thought I would get your feedback since your response was dead on with upgrades and what may work or won't work.

Thanks again for you input,
Dooger

 

[boatn70]

which boat do you have?

 

[vinny p.]

If you can get a good deal on a used set of CMI's, I say go for it. However, I would not cut the deal until the headers are sent back to CMI for a leak check. If they check out good, then great. How old are the headers? Do they have cool collar? I am not sure what hull you have. You say its a 26' Persuader? In any case, any 25 or 26 Checkmate HULL , is going to handle any power you can throw at it. The question is how is the hull set up? I would not recommend going any faster than 70 mph without hydraulic steering. A good inspection of the gimbal is imperative. Loosing steering at speed, wouldnt make for a fun day on the water. If the gimbal has any play, fix it NOW.
A good set of aftermarket tabs is next on the list. You said you may want to open the exhaust. What exactly do you mean? Simply porting the exhaust ports? If that is the caes, it wont do a damn thing for you. Going through the trouble of removing the heads, just to port the exhaust ports, doesnt make sense to me.
As I have said here many times before, which has gotten me into trouble here, its the incidentals that add up. Going fast on the water is not as simple as adding a cam and headers. There is alot more to it, to do it safely and efficiently.

 

[happy]

happy new year to all, and its good to be back home...

I've read all the threads on this one, and i may have confused some, or mixed them up.. but i'm sure i'll be straightend out on them soon.

as far as beating the powerplay, you'll have your hands full, beating the thunder will depend on who can take the most beating, and all the thunders i've driven are light and on the squirlly side, this would be on your advantage..

based on what i read your trying to keep up with the pack instead of the continious fallying back, and back .. considering your budgett you sent out, perhaps you should consider beefing up your mid range and being able to maintain a set goal speed, and base your future mods on what you have in the engine, and not outside the engine.

another option is to look for an engine pull out (and they happen all the time) which is going to be sold for what ever they can get, vs spending the money retroing.. you need to keep your eyes open cause you can get 525efis cheap , full dress.. with full factory warranty.. keep your eyes open

if your set on building your own.. start on the inside of the engine and build from there.. buy all the components fixed on a set outcome.. building outside in costs more.

the addage speed cost money is true, hp, that cost money too, i reccomend settling somewhere where your comfortable, the speed demon can consume the best of us, however, i'd rather do a solid 80 all day than 100 for ten minutes..

just a lil food for thought..