Captain YARRR

Hey everyone,

This is a long ways off, but I think it would be an interesting conversation. I have got both of my engines running smooth now, so this is going to be my year of reliability. Maybe next year I'll get itchy for upgrades.

I am pretty happy with the performance of my boat right now, I am getting low 70s with my twin 6.2 MPI Dominator. But I am curious, has anyone upgraded the heads and cam on these engines? How were the results? What heads and cam were used?

I know these threads are bait for the big block fans to come out and tout small blocks being a waste of time. But let's get down to it: I am pretty happy right now, extra speed is always fun and heads/cam is much cheaper than new engines. Right now my boat already surprises people, a little more surprise would be fun.

Knot 4 Me

Contact Bob Lloyd at Full Throttle Marine (www.fullthrottlemarine.com). I believe he has done a few 6.2's in various boats.

Wes Burmark

I have twin 6.2s in my Fountain. I looked into possibly warming up the stock combo and the good advise I got on this forum was not encouraging. It seems the stock heads do not flow much past .480 lift and the valve guides are tall enough so even a swap to 1:60 ratio rockers is not possible without changing to beehive valve springs. The intake is a bottleneck and the throttle body will need to be relaced too. Then there will be a computer reprogram needed. If you look at the specs on the 383 Stroker Scorpion (A remanufactured Mercury engine no longer available) they used RHS iron heads, 1:60 rockers, 9.5 forged pistons (91 rated fuel needed). They also use a Scorpion intake that was about $500 each and had limited availability. If you are already in the low 70 m.p.h. range you are doing great. IMO there is no inexpensive solutions beyond prop blueprinting. By all means check with the experts (which I am NOT!). I would move up to a bigger boat with big blocks if I wanted to go faster at this point. Let me know if you decide to build up your 6.2s. I'd be curious to read what you do and how it all works out.

Captain YARRR

I suppose it depends on what budget you are working on if it makes sense. If I were to get in to it, I would expect to replace those parts because those are pretty typical for any engine upgrade.

Looks like top quality new heads can be had for $1500-2000, I expect a cam around $500, associated other parts probably around $1000. Under $5k an engine would be inexpensive compared to an engine swap or a boat upgrade.

cp5899

iTrader: (1)

Is the 6.2 an LS based engine? If so, there is a huge aftermarket for the LS motor and I would think it would be easy to find power.

But, I don't know what the 6.2 is so I'm probably way off.

Captain YARRR

Man I wish, I have had LSx based vehicles since I was 16 and know them extremely well. They are easy to make more power because of that aftermarket and cheap. The 6.2 MPIs are not LSx unfortunately. I am not sure what they are categorized as though. Anyone?

Expensive Date

We have had a lot of discussions on here about the 6.2s. It always comes back to the heads and manifold (F.I. system) are very restrictive. Unless you are procharging the need to be changed if you want any real gains.

Wes Burmark

The 6.2mpi is a standard 350 block with a 1/4" stroker crank for 377 c.i. I believe for 5k per motor you could probably build a 425 h.p. version. With twins you would gain about 10 m.p.h. after springing for new props. I'm happy with mine stock tho I could be tempted to do the props if ever I ding one or two.

bobl

Your heads are not bad. The intake is the weak link, unless you have the early 6.2's with the 4 bbl type intake. I did a 6.2 a few years ago. Some port work, cam change, roller rockers, after market intake and stainless marine exhaust. It was before I had a dyno so I'm not sure of HP, but the boat picked up a solid 5-6 mph.

Bob Lloyd

Trash

Look around for a Scorpion intake (as mentioned) system. I don't believe they will be limiting. I believe there are actually two styles. One from around 1995 (pre Scorpion line) that fits non-Vortec style heads. The later one fits the vortec style heads. The throttle body on the 1995 style was the same TB used on the 454 and 502 MAG EFI/MP motors.