5.0 to 5.7 350 Mag Swap worth it?

[pmtom1]

So this spring I bought a 2007 Chaparral 246 (4200lbs empty) with a 5.0 and Alpha 1 Gen 2. I knew it was going to be under powered but the boat is super clean, EXACTLY what we were looking for (except power) and it was great deal so if I had to put money in, Id still be inline with values. After messing with 4 different props I found the right size that gives me OK holeshot and I top out at 40 MPH in most circumstances.

Started reading all the engine swap threads and don't think I want to push the Alpha to much with a 383 or drop the cash on on a bravo upgrade so thinking about 350 mag. I found some REALLY good deals out there but wondering if the 25-35 HP is really gonna be noticeable and therefor ...worth it.

I know Im never gonna see 50 mph but what SHOULD I expect out of the extra HP? thanks for the advice / opinions!

 

[pmtom1]

..Oh and we use the boat mainly for cruising the CT river, some mild tubing / knee boarding and occasionally hit the Long Island sound.

I will doing the swap myself so no labor. Pulled a couple boats engines before and not too worried about this swap from what ive read here.

 

[jimmbo]

At 24 ft, I would be looking for something with more low end torque than a 5.7 litre. A 7.4 would be my starting point, granted the Alpha would need to be replaced as well.

 

[Scott Danforth]

I would go with a stroker if you plan on staying small block or go to a big block like Jim mentioned. a boat that heavy should have had the 6.2 from day one.

 

[Bondo]

but wondering if the 25-35 HP is really gonna be noticeable and therefor ...worth it.

Ayuh,..... 35 hp increase Is noticeable,.....

You'll probably only pick up a couple or a few mph top end, but you'll get there quicker,.....

 

[QBhoy]

Be 40 hp difference and noticeable.

 

[Rick Stephens]

Vote for a 383.

 

[spunkyman]

I upgraded my 5.0 to a 350 MAG... save yourself the headache and get a complete drop in if you do so..... otherwise, trying to match a long block with the other parts from your 5L, will drain you in headaches, frustrations and big bucks in labour. Not to mention $1600 for the ECM alone. Also, the Alpha to Bravo is also gonna be labour intensive and drain you of cash !!

 

[AShipShow]

Another vote for 383... probably by far the most straight forward and best bang for your buck option

 

[alldodge]

Your boat weights more then my Rinker and it needs a Bravo 3 drive with a SB (383), or B1/B3 with BB. Could look for damaged hull (insurance)

Sell the boat and get one with more power.

 

[Cobe Marine]

So this spring I bought a 2007 Chaparral 246 (4200lbs empty) with a 5.0 and Alpha 1 Gen 2. I knew it was going to be under powered but the boat is super clean, EXACTLY what we were looking for (except power) and it was great deal so if I had to put money in, Id still be inline with values. After messing with 4 different props I found the right size that gives me OK holeshot and I top out at 40 MPH in most circumstances.

Started reading all the engine swap threads and don't think I want to push the Alpha to much with a 383 or drop the cash on on a bravo upgrade so thinking about 350 mag. I found some REALLY good deals out there but wondering if the 25-35 HP is really gonna be noticeable and therefor ...worth it.

I know Im never gonna see 50 mph but what SHOULD I expect out of the extra HP? thanks for the advice / opinions!

1) Putting in the 383 at 350hp would be really pushing the limits of that Alpha, which is why Merc shows their 383's as being used with Bravos (also, the 383's have more torque than the 7.4 base mods) 2) You were referring to a "350 MAG" so guessing you are looking for good used takeouts as, technically, they are no longer in production. The current mod would be their Plus Series 350MPI-ALPHA (#863611R11) which is 300hp, has the same 10 pin harness and Alpha shift interrupt plate as your 5.0 so essentially "plug and play". But you're looking at $9k plus....so not sure if that's within the budget. You didn't say so I'm assuming your 2007 5.0 is carbed (2brl that year) so if I recall they were only rated at 210hp (?). IMO, this 90hp gain is HUGE......we're talking 30% HP upgrade. But agian, do you have $10k room to put into this boat? Food for thought, good luck!

 

[alldodge]

the 383's have more torque than the 7.4 base mods

Tell us where that shows up?

Merc 383 reman 350hp 390Tq
Merc 454 330hp 405Tq

Also you get close to 400Tq at 2000 rpm, where the 383 needs to get to 3800rpm. Need to get up on plane

Boat Test

MerCruiser 383 MAG Stroker develops 350 horsepower and 390 ft-lb. of torque at 3800 rpms. It breathes through a long runner intake manifold with multi-port fuel injection, and is driven by the latest 555 ECM (electronic control module) with SmartCraft.

 

[QBhoy]

1) Putting in the 383 at 350hp would be really pushing the limits of that Alpha, which is why Merc shows their 383's as being used with Bravos (also, the 383's have more torque than the 7.4 base mods) 2) You were referring to a "350 MAG" so guessing you are looking for good used takeouts as, technically, they are no longer in production. The current mod would be their Plus Series 350MPI-ALPHA (#863611R11) which is 300hp, has the same 10 pin harness and Alpha shift interrupt plate as your 5.0 so essentially "plug and play". But you're looking at $9k plus....so not sure if that's within the budget. You didn't say so I'm assuming your 2007 5.0 is carbed (2brl that year) so if I recall they were only rated at 210hp (?). IMO, this 90hp gain is HUGE......we're talking 30% HP upgrade. But agian, do you have $10k room to put into this boat? Food for thought, good luck!

I may be wrong but I assumed he meant going from a 260hp 5.0 mpi to a 350 mpi at 300hp.

Would need an new ecu at least with it.

 

[pmtom1]

thanks for the advice!!

Yes... I have the 5.0 MPI @ 260hp. I'm searching the wreck sites daily because I need a trailer too. So if could find a trailer, bigger motor and a bravo 3 for 6-8k, I'd still be way under book value on the boat with what I paid. Then I could sell my 5.0 and alpha. And more importantly, id be happy for 4-5 years. Frankly, its not TOO bad now.

The reason for my question was i had found a 350 mag with under 300 hours pretty cheap. ($4,000). I'm not afraid of drilling a hole here and there to get the bravo three performance and the headroom for a bigger engine....but the 350 mag would be a super quick and easy upgrade and would end up costing me peanuts after I sell my 5.0.

I am pretty convinced to do a complete drop in regardless of where I go. Aside from the headaches... I think I can get back what I spend by selling mine.

 

[AShipShow]

So re-reading your original posts, if you are just cruising/tubing/kneeboarding/etc... then what are you really after with the extra 40HP? I would think 40HP is definately going to make a difference, but it still might now give you enough to make you happy...
Sounds to me like if you REALLY wanna go faster you need to jump on the bravo/bigblock wagon... Most planing hulls of that size are going to come factory with a bravo setup, so you already know thats what you SHOULD have.

 

[Scott06]

I have a friend who has a 24 ft crow line deck boat similar in size his has a 350 mag and B3 drive. With both our families (9 ppl total) on it is adequate for skiing tubing etc. bottom line I think you would absolutely notice the performance improvement with swapping in the 350 mag. It wouldn’t be an ideal power plant for that boat but probably a relatively economical solution when proped correctly.

One thing to check is if 350 mag is set up for alpha or bravo, as you need shift interrupt if you are keeping the alpha. Or were you going to go right to the bravo drive?

I would think your take out 5.0 mpi if complete and assuming good compression and oil pressure would get the same price as the 350 mag

 

[QBhoy]

thanks for the advice!!

Yes... I have the 5.0 MPI @ 260hp. I'm searching the wreck sites daily because I need a trailer too. So if could find a trailer, bigger motor and a bravo 3 for 6-8k, I'd still be way under book value on the boat with what I paid. Then I could sell my 5.0 and alpha. And more importantly, id be happy for 4-5 years. Frankly, its not TOO bad now.

The reason for my question was i had found a 350 mag with under 300 hours pretty cheap. ($4,000). I'm not afraid of drilling a hole here and there to get the bravo three performance and the headroom for a bigger engine....but the 350 mag would be a super quick and easy upgrade and would end up costing me peanuts after I sell my 5.0.

I am pretty convinced to do a complete drop in regardless of where I go. Aside from the headaches... I think I can get back what I spend by selling mine.

You won’t need to change the alpha for a bravo 3 for a 350 mpi change. In fact the alpha will run quicker than the bravo, if you get it propped right.

 

[QBhoy]

But the bravo might help out the hole if your boat is on the heavy side. A huge extra expense though.

 

[Cobe Marine]

1) Putting in the 383 at 350hp would be really pushing the limits of that Alpha, which is why Merc shows their 383's as being used with Bravos (also, the 383's have more torque than the 7.4 base mods) 2) You were referring to a "350 MAG" so guessing you are looking for good used takeouts as, technically, they are no longer in production. The current mod would be their Plus Series 350MPI-ALPHA (#863611R11) which is 300hp, has the same 10 pin harness and Alpha shift interrupt plate as your 5.0 so essentially "plug and play". But you're looking at $9k plus....so not sure if that's within the budget. You didn't say so I'm assuming your 2007 5.0 is carbed (2brl that year) so if I recall they were only rated at 210hp (?). IMO, this 90hp gain is HUGE......we're talking 30% HP upgrade. But agian, do you have $10k room to put into this boat? Food for thought, good luck!

The unit I was referring to was the 383 MAG BRAVO, part #865108r90. From Merc website: [h=2]383 MAG Bravo 4V[/h]
350 Crankshaft Horsepower

Same power and more torque than a 454 HO carbureted engine. This torque monster delivers 429 ft-lbs of raw torque at 3800 RPM to launch even the heaviest boats with authority. When equipped with the same marine exhaust headers as found on the 383 Scorpion®, this engine produces 370 HP and 456 ft-lbs of torque—more than a 502 carbureted engine. This is the ideal replacement engine for 454HO and 502 HO carbureted engines that power cruisers, large runabouts, and sport boats. Marine exhaust headers sold separately.

 

[Cobe Marine]

Tell us where that shows up?

Merc 383 reman 350hp 390Tq
Merc 454 330hp 405Tq

Also you get close to 400Tq at 2000 rpm, where the 383 needs to get to 3800rpm. Need to get up on plane

Boat Test

I was referring to the 383 MAG BRAVO 4V #865108r90: [h=2]383 MAG Bravo 4V[/h]
350 Crankshaft Horsepower

Same power and more torque than a 454 HO carbureted engine. This torque monster delivers 429 ft-lbs of raw torque at 3800 RPM to launch even the heaviest boats with authority. When equipped with the same marine exhaust headers as found on the 383 Scorpion®, this engine produces 370 HP and 456 ft-lbs of torque—more than a 502 carbureted engine. This is the ideal replacement engine for 454HO and 502 HO carbureted engines that power cruisers, large runabouts, and sport boats. Marine exhaust headers sold separately.