Engine Prep Difference?

[GAWnCA]

I've got a question and it doesn't concern the engine type or make, so I hope this doesn't become a battle over which engine make is better than the other.
When it comes to boats in general, hot boats to be more specific, when comparing "JET" powered to "V" drive powered motors, is there a difference in the machining processes required? and, the kind of components that may be installed? how about clearances? I.E. Heads, pistons, valves, etc.

[DelawareDave]

I don't think you will find a lot of difference, except in how much time and effort the person building the motor wants to expend, when it comes to the little "details". Marine use engines generally make use of better quality parts, different clearances from automotive use, etc, due to more loading when under operating conditions. Of course, the higher the performance factor, there is usually a corresponding increase in throttle useage, etc, lol. :eek:

[GAWnCA]

I don't think you will find a lot of difference, except in how much time and effort the person building the motor wants to expend, when it comes to the little "details". Marine use engines generally make use of better quality parts, different clearances from automotive use, etc, due to more loading when under operating conditions. Of course, the higher the performance factor, there is usually a corresponding increase in throttle useage, etc, lol. :eek:
Thanks Dave, So I guess a hot rod marine motor, no matter if it's used in a jet or a "V" drive, they require the same specifications. Cool! I guess I'll start looking for a good BBF block and start from there. Greg

[LeE ss13]

Camshaft choices differ.

[058]

When it comes to boats in general, hot boats to be more specific, when comparing "JET" powered to "V" drive powered motors, is there a difference in the machining processes required? and, the kind of components that may be installed? how about clearances? I.E. Heads, pistons, valves, etc. The only issue between the V-drive and jetboat engine is the RPMs required for the application. A jetboat with a N/A engine will not, as a rule, spin much over 5500-6K whereas the V-drive can turn 7500-9000 depending on prop, gear ratio, hull, etc. An engine that isn't going to turn over 5.5-6K can get away with using stock parts and tighter clearances. An engine set up to spin 8+K will need much better parts and looser clearances than stock if you like to sleep well at night.:D V-drive: Forged pistons are a must as well as premium rods, steel crank, 4 bolt block, bulletproof valvetrain and related parts, cylinder heads and induction to support the 8K rpms, ignition, exhaust and the list goes on. Speed cost money...how fast do you want to go?

[ck7684]

Marine engines differ mainly due to the cooling system. When the engine is contantly running cold water through it, the block doesnt expand as much as the pistons, and therefore need more clearance for piston expansion. The rest such as camshaft selection etc. is going to be application specific, such as RPM range, exhaust type, etc.
Other marine items may be made from corrosion resistant materials due to wet environment boats are subjected to...

[GAWnCA]

Great info, and if and when I do get to build I'll be back to ask more questions. I'll be building on a Ford 460 block, if that helps. Thanks!! Greg :)

[DelawareDave]

I'll be building on a Ford 460 block, if that helps. Thanks!! Greg :)
I thought you didn't want to start any battles about which is better, etc! :D

[GAWnCA]

I thought you didn't want to start any battles about which is better, etc! :D
No battles, just stating my preference. ;)

[jkh04200]

Chevy man to the bone.
BUUUUUUUUTTTTTTT I have seen first hand how easy it is to make some serious HP from a 460.

[SmokinLowriderSS]

Run your bearing and ring gap clearances on the wider 1/2 of the stock factory clearance specs and those items will give you no trouble.
There really should be no major differences in engine build from a v-drive to a jet, other than the RPM expectations mentioned above, cam grind selection and valvetrain parts.

[Boostedballs]

The only issue between the V-drive and jetboat engine is the RPMs required for the application. A jetboat with a N/A engine will not, as a rule, spin much over 5500-6K whereas the V-drive can turn 7500-9000 depending on prop, gear ratio, hull, etc. An engine that isn't going to turn over 5.5-6K can get away with using stock parts and tighter clearances. An engine set up to spin 8+K will need much better parts and looser clearances than stock if you like to sleep well at night.:D V-drive: Forged pistons are a must as well as premium rods, steel crank, 4 bolt block, bulletproof valvetrain and related parts, cylinder heads and induction to support the 8K rpms, ignition, exhaust and the list goes on. Speed cost money...how fast do you want to go?
please correct me if I'm wrong-
I think a jet bottom end needs to be at least as tough as a V-drive bottom end. The V-drive has long shafts to absorb some shock loading. The jet pump has a short shaft that does nothing for absorbing the shock. And to top it off, I think pumps have more shock loading to deal with because the pump inlet doesn't sit as low in the water as a prop does. When you are screaming across choppy water in a jetboat, your impellor will see zero load, then max load, again and again...
The V-drive bottom end needs to be built tough because it will probably turn faster. IF it's properly balanced, I don't think it compares to the shock load of having a pump attached to it.
In either case, it's not a car engine and it must be built to higher and different standards; The bottom end is no place to pinch pennies.