350 mag mpi engine upgrade options?
 

I have a 2004 21 lightning with a 350 mag mpi & bravo 1 setup. I'm looking for options to get more speed out of the boat with possibly an engine upgrade. The current motor only has 200 or so hours on it and runs good but just not fast enough for me anymore. I played with alot of props with the help of Brian at Valley prop in Ventura and I'm where I need to be RPM wise (4800 - 5200) 17 - 19 pitch. The best I've seen out of the boat was 55mph with 3 people and low on fuel. Most of the time I run around with 5 people, somewhat loaded down, a big stereo system and hit about 51mph.

What are my options with wanting to stay turn key and reliable? I've heard some people mention whipples and prochargers and also had some people mention the 383 stroker upgrade engines? I'd love to see the boat run 65 - 70 or more.

My mechanic has looked over my current motor many times and says there is absolutely nothing wrong with it. I just need more horsepower I guess to turn a bigger prop to get more speed?

I talked to one of the builders of these boats (John West) and he said I should be able to run a Merc High Five 21p all day long at 60mph. I tried this prop first, could only pull 4200 RPM at 50mph and it was a dog out of the hole. Currently I'm running a 17p 4 blade Solas.

I have not had the engine put on a dyno, I don't know about place around me (Ventura County, CA) that has one.

Any advice without breaking the bank?

Sell the smallblock, and buy a bigger motor, it'll end up quicker, and a lot cheaper than trying to mod your current motor.

heads-cam-exhaust-intake. you will get about 100-150 hp. boat will do 10 to 12 mph faster. engine won't last 1 season. if u wanna go 70, get a big block...

[QUOTE=dereknkathy;3837900]engine won't last 1 season.QUOTE]

Can you explain this statement?

You need an additional 250-300 horsepower to reach your 70 m.p.h. goal. It would make better sense to me to look for another boat with the performance numbers you desire. A 27' Fountain with a big block would hit an easy 65-70 bone stock. While I'm sure you could build a 500-600 h.p. small block (454 stroker motor with supercharger) and reach your goal with your current boat I think the tab would be huge and the motor would need 92 octane fuel and lots of attention.

I was able to gain an additional 12 mph out of a modified small block (350 converted to a stroker) with a much slower and heavier hull. This motor is still going strong and for more than one season.

I don't think I can get much more unless I really get radical on the cam & compression which would then hamper driveablility.

To get to 70 you'd want to get a big block. This is probably your best route.

You have the Bravo so drive capacity is a non issue. Look for a 6.2 marine take out and tweak it to 450~500 horsepower and about the same torque numbers...and torque is where it's at in a boat.. You won't be adding any weight and will have tremendous potential. If you shop hard you can find one for $2K~$3K complete. You could put the same $ in that 350 and see 400+ # of torque but that's not enough to put you where you want to be.

A big block in a boat that size is always going to be ass heavy...period. I have seen it done in F3 Formulas with success but they won't run 70 and with the extra weight in the stern they become a handful. This is my suggestion if you want to keep the boat.

As Wes suggested...dollar for dollar you are better in the long run to sell your boat and buy something larger with twins or a stout big block.

like mentioned...pull yous and sell it complete...you cant tune the pcm on that engine to make it worth a chit! if you just want a reliable faster package look for a 496HO with lowe hours on it..that should put you at 65 mph..

I leaned on the 350s in my former ChrisCraft Stinger260. I got a 4-5 m.p.h. increase updating heads, intake, cam with roller rockers, and rejetting the Quadrajet carbs. I also added taller flame arresters and stepped up from 21" clever 3 blades to 23" clever 3 blades. It was expensive times two! (Not sure HOW Trash got a 12 mph increase w/his 350 hop-up...) I now have a 29' Fountain with twin 6.2s. To increase the output of these engines would require a "whole package" as the stock state of tune has a combination of well coordinated parts. This is not my opinion but the opinion of professionals who contribute to this site and build engines for a living. The 6.2s are 20 h.p. stronger than the 5.7 m.p.i. with about an equal increase in torque. They made a high output version of the 6.2s for a time. The rating was between 350 h.p. (probably VERY conservative) and 420 h.p. (a Mercruiser aftermarket build with CMI headers - required 92 octane). If I had a boat with a tired 350 I would not hesitate to replace the 350 with the 377. But the additional 20 or so h.p. is not going to make a huge difference in the performance of your current boat. A hop-up of the 6.2 would require at least 2k in parts (cam & kit, heads, intake, throttle body) plus the rebuild, machining, and labor. If someday I want more performance than my current 29' Fever I'll purchase a faster boat. JMO

i agree,a hp500 is a 200 hp increase and will net you at least 10 mph faster,and is a much better starting point if you want to go up above the 500 hp range,building the small block to produce over 500 hp is just not cost effactive.