Thread: Marine Application

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My buddy and I are doing a 350 buildup for a 21 ft. boat. I want to tune the engine for the high rpm band because that is where it will spend most of it's time. We don't want to dump a lot of money into it (of course). The chambers and pistons look good. We will get a new cam and intake but want to try to use a set of heads we have. I think the one set are 76cc 350 heads. I'm checking on the other set. I guess my questions are seeing my probable block/head combo and my goals, what should I look for in a cam and intake? Second is there anything else I should be considering since this is a marine application and will be at wot a lot? Thanks. ---Rich

OK we just grabbed a Torquer II intake with a Holley 650 Dp carb. From what I've read this should be a good high rpm manifold. Now the million dollar question is what cam? Also I'm hoping I'm correct in thinking I can bolt the pre 1973 heads on an 1988 block. I am correct aren't I? ---Rich

I've seen aluminum intakes lined with brass or something of similar color for marine purposes with salt water cooling. If your boat is a trailer boat and you flush the cooling system after you take it out of the water, you'll be fine with standard automotive parts.

Another option possibly? The boat has a somewhat rebuilt 307 in it now with low hours that's been bored .40 and has pretty new pistons. We just ripped it apart and it looks pretty clean. I have a stock 88 350 high miles. Can I move the crank from the 88 350 into the freshed 68-73 307 block? It's the same block itself isn't it? Would the rods still be the right length still? 350 heads were on the 307. We'll clean them up.

No, you can't put the 350 crank in the 307 block without changing either the rods or pistons.

My dad's new boat has a heat exchanger, which does the same thing as a radiator but, is not cooled by air, the coolant ( same coolant as regular radiator ) is cooled by sea water pumped into a second tank in between the inside tank ( contaning radiator coolant ) and the outside of the exchanger itself so, no sea water gets into the engine, just cools just like a normal radiated engine is cooled ( cept basicly being a water cooled radiator ) though, his motor is a 488 Mercrusier L4, it all depends on the cooling system of the boat.

Build for mid range torque, not high end RPM. Boats need torque. Is this engine going in a jetboat or eggbeater? I've seen many car guys get into our sport and have these great claims of having a killer engine that they will be putting in their boats, only to be very dissapointed with it's performance.

Small blocks are what I run. We shoot for a RPM of 5500. In these Eagle hulls they work great. We get 98 MPH out of 565 HP. Torque is over 500 ft/lbs from 3200 rpm through to 5100 rpm. This is my 434ci small block powered race boat.

It is way too much fun. It's the last refuge of "no speed laws apply" I can go boating any time I want and run as fast as I need or feel like. I was taking plenty tickets with my old Camaro and this just felt like the thing to do. I have seen several small block build ups, but none would work that great in a boat. Cars have the benefit of gears. Boats don't. Our races generaly are 70 - 100 mile legs in one day X 6/7 days for a total of 500 miles. To run a engine at 6500 / 6900 RPM, there's a good chance that parts are going to come apart. Some have tried and many have failed. Like in any race; you need to finish to win. Those UFO are geese!! You should see the pelicans try to get out of the way! We smoked one in Mexico in 2002. Here's another shot, from New Zealand in 2001

Here's one more. Just let me know if I'm hijacking the thread. BUT, Motor heads and motor heads, be them in a car or boat!! This is 2003's winning engine - Nasty 468ci 780 HP, profiler headed engine. Boat ran 115 MPH.
Link to more: www.eagleracing.ca

Darn things got wings!

That is too sweet!! I know what you mean about the freedom on the water. I've been running a modded Seadoo that hits about 73 on glass. Some friends have a sick twin 454 speedboat. I asked about the handle in front of my seat. I found out how neccesary it is once we took off. Last couple of years we ran around in a dog 25 ft cabin cruiser. It was cool but s...l...o...w. Took forever to plane with people on board. We traded it for this 21 foot little speedster. As for our project boat, It's prop driven. I'm starting with the worked 350 and see how it feels. The 307 in it was pretty weak at the top end. Low end torque wasn't bad but it had been sitting for three or four years and we figured it was a good time to rip it apart. I guess my idea of the start of high rpm band is your mid range so we're still on the same page. The Torker II intake is supposedly good for mid to high rpms(2500-6500 RPM). I'm just unsure how much cam to go with on the setup.

Hey Bald Eagle, I got a simple question for ya, why do the stainless steel props make a boat go 4-5 miles an hour faster than the cheap painted props? Just wonderin.

Heres my dad's new boat, a 1984 Imperial VC230 powered by a 488 Mercruiser L4 rated for 180 Hp, it isn't very fast, on plain it will reach about 55 MPH, but my dad bought it as a fishing boat and, that's actually what it was designed for, it has 2 livewells and came with 2 fishfinders, 2 raido's and it is wired for 12 volt and shore power. It runs 2 tanks =ing 85 gallons.

Originally posted by Matt167
Hey Bald Eagle, I got a simple question for ya, why do the stainless steel props make a boat go 4-5 miles an hour faster than the cheap painted props? Just wonderin.

Can't comment a bunch on props; I'm a jet guy. But a good stainless impeller will normally out perform a cheapo aluminum one, because there is more time and effort put into it. It makes for a smoother surface with in turns reduces friction. Just one photo then I'll quit.

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