SC V6 or MPI V8?

About inboard or outboard motors.

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Denon Osterman
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Post by Denon Osterman »

well i'll take your word for it. but im confused...i would have thought jets would have favored high RPM's, because then the velocity of the water beeing shot out(and there for max top speed) is raised.

who wants to explain in professional terms how a big block V8 is the safest/most reliable option???

and so then caber, IYHO, what would be the best engine?

what would you use if money was no object, but reliability was prime concern, as long as top speed was 70-80

Denon

rasorinc
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money is no object

Post by rasorinc »

CRUSADERS CRUSADERS CRUSADERS V-8s
Wood lasts generations.

Denon Osterman
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Post by Denon Osterman »

CRUSADERS CRUSADERS CRUSADERS V-8s
man do you work for them or something?

rasorinc
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No NO NO

Post by rasorinc »

They are simply the best gas engines on the market and have been since the 1950s. There is a reason Chris Craft painted their engines Crusader Blue. 50 year old boats still have original Crusaders although they may be rebuilt. See my posts and links under Boat Power. especially the links.
Pure touble free, clean operation, touble free for decades.
Wood lasts generations.

Denon Osterman
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Post by Denon Osterman »

I read the links. One of them was from back when EFI was bad, not good. They may very well be good engines, but they do not offer the power/weight ratio that other companies with 3 year unlimited warranties do, and so for my purposes, they are not ideal.

to be honest, i was more thinking something like this:

http://cgi.ebay.com/ebaymotors/Big-Bloc ... ccessories

but the michigan motorz 8.1 HO doesnt look that bad. a bit long tho, not very flashy

the indmar dont have any specs listed...look nice though, anyone know what they put out?
Last edited by Denon Osterman on Fri Jan 16, 2009 7:04 pm, edited 1 time in total.

Nova SS
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Post by Nova SS »

remember the clearances on a motor built for a car will be a little too tight for a marine application

Denon Osterman
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Post by Denon Osterman »

My bad. fixed the link to a "marine spec" engine

Denon

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kens
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Post by kens »

Denon wrote:
"who wants to explain in professional terms how a big block V8 is the safest/most reliable option??? "

I'll take a shot at this one.......it's the K.I.S.S. method.
Keep It Simple Stu...
A simple BigBlock with MPI fueling is by far simpler than taking a smaller displacement and trying to cram more HP out of it. you keep saying you want reliability, then you say you want high HP out of small displacement. It is just 2 different equasions dude.......then you say you want TORQUE. Well, nothing makes torque like HP@low RPM. A big block making 300hp @ 4200 is more reliable tq than a blown V6 making HP @ 6000.
Its just a math formula that you cannot get around.
HPx5252 divided by rpm=torque........no way around it.

rasorinc
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Post by rasorinc »

Car engines are not built like marine engines. A Hot Rod car engine will not last long. But that's O K if you don't mind replacing it.
Wood lasts generations.

Denon Osterman
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Post by Denon Osterman »

rasorinc,

I had mistankenly posted a link to a car engine, it has now been replaced with that of a purpose built marine engine-albeit not a crusader one. though it may not be thoroughly built to marine specs, whichever engine we end up purchasing will, for sure, be purpose built for a marine environment, if we do not end up buying a premade engine from a company such as michigan motorz, mercury, crusader, indmar, etc.

Denon

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Rich Coey
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Post by Rich Coey »

Kens is right.

Go with a marine big-block. Jets are very power-hungry. If you want it to be reliable, that's the way to go.

Rich

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Caber-Feidh
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Post by Caber-Feidh »

A Jet engine is not a real "marine" type engine either, the environment is the same, but that is where it ends. you will forever regret trying to make a regular marine-type engine (setup for prop) turn a performance-jet well. I guess it is fine for a regatta with the old geezers, or a flotilla for the water carnival.

If it were me, and I were looking to move fast, not break the bank... too bad, and look reasonably good doing it I would look at a 454 crate engine, carb and low open plenum manifold, spinning an AA or A+ impeller cut. On most any lightweight jet you will be well into the high 60's, maybe low 70's with the pump setup well. If I were spending like a semi-drunken sailor I would be looking at a 502T. and a 9.25" pump, little taller intake, exhaust is going to be critical with any 500 cube+ engine. Over the 500 HP barrier things start getting expensive fast.

Cheap way, look for a 454-powered truck toasted somewhere, install forged pistons, and jet cam, marine starter & fuel pump... you are ready to go.

The actual weight of a small block is only between 100 & 180 pounds lighter. In the case of a 454HO with alloy heads it's about 100 more than an iron 350. I am really not sure why everyone thinks there is such a big dif. (now back in the "old days" an all-iron LS6 vs a 350, there was a significant difference, but never near 400 pounds.) The advantages of using a stock & common displacement is the ready availability of performance marine-parts. Something sadly lacking from the vortec line.

Denon Osterman
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Post by Denon Osterman »

502T.
whats the "T." for?

If we end up going the 454 crate route, why not MPI? and if we do go down that road, would you be able to help with specific parts? I'm ashamed to regret i don't know engine specifics nearly well enough :oops:

high 60's/low 70's is perfect

what width do the stringers have to be for a 454?

Thanks,
Denon

rasorinc
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motor mount

Post by rasorinc »

If you want the engine to sit low with the oil pan down between the motor stringers I would use 2 x 8s with 1/2" ply on the outside of each stringer--and the whole length of the stringer. In addition I would use 2" x 3" x 3/16" steel angle to mount the motor mounts. I would run these long both fore and aft bolted through the 2 x 8s to spread the torque out a bit.I was not able to find a measurment for the width of the motor mounts. They will only bolt through the steel angle not the stringers. Stan
PS If you use aluminum angle go to 3/8s" thick stock and I would use 6061 or nothing less than 5086
Wood lasts generations.

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Caber-Feidh
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Post by Caber-Feidh »

the "T" signifies a tall deck block. (common error is to think truck). All tall decks are 4-bolt (although I have never seen a GM big block drop a crank in a normal marine app, it's still a good point to have them. The 4-bolt caps spread the stress over 2/3 more thread contact area, not to mention reduced stress on the web. Not so critical on the SBC (imho)but the mass in motion is getting pretty high on the big motors.

The deck of a tall engine adds about 1/2" to the cylinder length. It is of great value if you ever want to build a stroker... but more, since the crank sits lower in relation to the wrist pin and uses a longer rod, the maximum angle of the connecting rod swing is lower, it reduces lateral loading on the piston web, pin and skirt, not to mention helps keep the cylinders from undue wear.

It does cost engine height, but with a boat, that is not so critical.

I've owned both EFI and carb engines. From the standpoint of jump in & hit the key, EFI is a little better, it starts easier, but that's where it ends. My dominators are a fuel line and a throttle, no wires, solenoids, mass airflow, injector, regulator, and sensor shinnanigre. They tend to run a little less efficient, but a "field repair" involves beating it with a shoe to free a stuck float, or the famous rev-it-to-4k & cover-the-carb fix. Carbs cost less, and are not prone to moisture related electrical/sensor failure. A carb failure usually leaves an engine operating, but badly. ANY failure with the above injection shinnanigre causes a complete halt to the system. Heck, maybe I just like smelling like gasoline. It sure beats smelling of elderberries... or burned hair, believe me.

Incidentally, the 71-series blower designation came from GM's 2-smoker diesel engines. Each cylinder was 71 CID, and the engines were designated by the number of cylinders. a 3-71 was a 3-cyl, and so on. It has zip to do with blower actual/true displacement. There was also a 53CID series, but it's been a LLLLOOOONNNNGGGG time since I laid eyes on one. They were cute little buggers. Some even had a bypass circuit built into the rear of the case. I would forget the 71-series if I were looking for a reliable long-haul engine. they were never designed for the stresses of marine & gasoline. I love 'em, but they are not for the non-gear-head.

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