2 LS1's

One thing not mentioned is with small blocks you can buy two new ones for less than the cost of one new big block.That is a plus.Suprisied to hear that the twins are faster though.Good luck with your search I would not own a single engine prefer twins.

Good thinking. Put in a set of 450hp all aluminum LS's and some shorty drives and you would have a fast and fuel efficient (at cruise) boat for not a lot of money. It would significantly reduce weight and drag at the same time while adding power.

For overall value and durability I'll stick with twin 350's any day...but the question to ask is: what are your goals? I prefer security, added weight, good cruise speed and range, and cheap replacement parts...

I say go with 2 540's.

No such thing as overkill! :drink:

Uncle Dave,
To answer your questions if the single was a good deal - yes i would buy a single, no doubt. Like i said pros and cons to both. If given the choice I would first search for twin small blocks first.

I would get the twin small blocks. In the long run the drives and engines will be more reliable and should last MUCH longer. The twins small blocks will cost about the same, maybe less, to replace than the 540.

Bottom line is, you COULD make a single as fast as a twin with stock engines, but the reliability factor of stock(or nearly stock) small blocks vs. what you would have to put into that single big block to get the same speed would be ridiculous, but the cool factor of a nasty blown BB would also be sick..

I have twins in my 242 and am very happy with it after rebuilding to 383's.

My 28ft Saber with twin built small blocks (470hp) out ran and out accelerated single big block boats when we raced in P4.
And the balance was great!!
Heck it even beat a few twin big block boats!!
Oh and this is a Old School straight bottom...

Pass on the 29 and buy a 32 with 496 HO's.

I have heard that singles are a little better balanced, but Wife + Kids + open ocean + twin 350 Mag = Peace of mind.

http://i809.photobucket.com/albums/z...ngtonBeach.jpg

I think the balance of a single engine is a catch 22. Obviously the rear of a twin is heavier, but the torque steer you get with a single can make the boat land on its side when it launches and will have a tendency to not run level. You will alway be messing with the tabs just to get it to drive level. In a twin, your just pointing the nose up or down. In a single your doing the same, but your also trying to get it level.

Were is that kryptonite video mastercraft posted. Watch when it launches the boat dipped to the starboard or port (can't remember) he didn't come down flat. I have had numerous bad landings trying to manage the torque steer of my old 24 python, which is why I sold it. The twin engine boat I have now is 5 times easier to drive, granted it doesn't have a pad bottom like the 24, but it was the torque steer that drove me nuts. Why do you think mercury made a special NXT drive just for single engine boats?

[QUOTE=TexomaPowerboater;3348219]I think the balance of a single engine is a catch 22. Obviously the rear of a twin is heavier, but the torque steer you get with a single can make the boat land on its side when it launches and will have a tendency to not run level. You will alway be messing with the tabs just to get it to drive level. In a twin, your just pointing the nose up or down. In a single your doing the same, but your also trying to get it level.QUOTE]

You hit the nail on the head with the torque steer. Plus i think the twins being a little heavier; give you a little softer ride in the rough.

Also, the fuel savings on a single engine boat vs a twin is not much. I would venture to say that a twin engine boat will use only 10-20% more fuel than a single at cruising speeds. That is because it takes 4000rpm on a single to do what 3000 rpm does for a twin application. Once you get past 3000-3200rpm the fuel consumption increases dramatically. This is also why the twin setup is often more reliable and can have more hours before rebuild.

Of course if you drive WOT all the time these facts go right out the window.

OHHHHHH.... so that is where the other twin SBC Savage is.:cool:

Tex, imo... your best post ever!:coolcowboy:

Great boat, 470HP, I seem to remember for you hunting for a drive a time or 2:evilb:

You are right the balance is a catch 22.
However - lighter is always better.

The singles do torque steer but a really good fully hydraulic steering system will minimize this - but it's its still there.

The original NXT "single skeg" was a disaster, and Merc changed it due to handling issues shortly after introduction.

Thing is ...small block parts - like exhaust systems aren't any cheaper than big block parts, and if you put in 2 potent small blocks you will spend very nearly if not more than what you will on big blocks on an HP to HP basis. The small block guy will still have a much harder time finding parts.

( I know because I built, and still own a potent small block boat)

So in a sense a good twin small block boat might as well be twin big blocks from a maintenance, cost and parts availability perspective.

True the small blocks are easier on the drives than the BB's.

From my ownership perpective having built both - the realistic choice is really a single BB or twin BB's.


Uncle Dave

Do you think 2 BB's will fit in the engine room of a Scarab 29 ?

Hydraulic steering does nothing to counteract the torque from a single propeller.

If we consider stock power you could compare stock 350 Mag MPIs (300 HP) to eg. a HP500, my guess is that most likely you will get many more hours out of the small blocks without any need to rebuild anything compared to a HP500.

If you want a lot more horsepower out of a stock setup I agree BB is the way to go.

Scarab 29 beam is 7' 6".

I honestly dont know if they would or not. Ive never crawled around inside an engine room of a scarab 29.

Good hydraulic steering does not "counteract" the torque, only an equal and opposite prop does that (our good buddy newton) but it makes a hell of difference in keeping the boat going straight because you dont "fight it" at the wheel itself or very minimally fight it at the wheel. The steering setup pays off huge in the ocean where you are always leaving the water and being pushed off course by directional current.

After boating with SB and BBC's about 30 years of my life I get about the same amount of hours out of both to be honest between 4-700 hours before a full rebuild. The small blocks work harder than the big blocks and typically spin faster to deliver a given level of HP and Torque- its all about the heads BBs simply breathe better.

I love my small blocks- but I dont save any money compared to a BBC I have a 500 HP small block right now. To make 500 HP out of a small block that has a nice flat torque curve and idles with good dockside manners but still pumps out the beans simply costs a lot of money. The marine parts market is geared toward BBC's plain and simple to you can rarely get good used SB parts.

You will save on drive maintenance costs with twin compared to a single for sure- (as long as they both have hydraulic steering) except that you have to buy and maintain 2 of them out of the gate.

Twin engine boats are really great, but its not twice the work, its like 4x the work, as different things go out on each engine at different times.

I've only "baby sat" boats with twins for several summers - never owned one.

Everything in the world of boats is a tradeoff.

Uncle Dave

I dont see twin BBC's fitting in a 7' 9" beam , atleast not to the point where you could work on them.. And you will work on them.. I dont know what you guys are talking about torque steer on singles... Tabs and or the right prop selection will minimize any ill effects of torque steering.. A single engine boat should fly just as level as a twin , if driven correctly. A boat that lands on it's side isn't because of a torque steer, its out of ballanced somewhere.... It's all in SETUP guy's...

Its true most crooked landings start with a crooked launch to begin with.

I would say that very few guys rigs actually make enough beans or hook up hard enough from a slip perspective to make it a relevant concern.

Drive a 8-900 HP blown single boat on a calm river or lake you can feel the boat roll on its side when you put your arm in it during a speed run when the prop is really hooked up.

Poll a few of the guys on this site with 100+ MPH single engine cats and see what they have to say about it.


Uncle Dave

I have had a 400 + hp donzi 18 classic and 700 + hp 24 baja.. setup makes all the difference

Those sound like great boats and Id like a ride!

Whats your setup advice to counteract Newtons 3rd law of motion ?




Uncle Dave

prop selection

I understand what you are saying, however the original question was:

what would be a better package in a late model 29 scarab ?
small blocks = 350 mpi's = 300 hp x 2
big block = 540 ci. 575 hp

My guess is that the stock 350 Mag MPI will go longer between rebuilds than the 540 ci. 575 HP.

So what prop will you advice for a Scarab 29 where the "torque" from a single propeller is elliminated ?

All things being equal in a 29 foot boat- I would pick the single BB because it will be easier to work, on easier to mod, and easier to find parts for. - and overall deliver much if not the same fun for less money and maintenance overall.

I do not believe you will get significantly longer if at all longer engine life out of twin small blocks , than a single big block.

I myself have participated in many threads where guys with twin small block are looking to rebuild or rework them for a few more MPH.

chase down my threads and look at the questions these owners are asking.

I typically tell the SB guys they really need to start with exhaust and they are shocked at the cost and end up just doing stock rebuilds.

Uncle Dave

http://www.offshoreonly.com/forums/g...ll-blocks.html

Heres is a classic twin small block thread started by a great guy with a great boat facing a dilemma.


Uncle Dave

It's trial and error.. On the donzi I had .. 4 blades were too much and I wound up finding a predator 3 blade that was awesome.. On the baja, the only 1 that worked right was a 4 blade Mach patriot..

?? We only blew one drive and that was while testing in Hollywood, Fl. It was a older style Bravo drive... (and I wasn't throttleing...:evilb: )

I did do some searching to find what lowers the boat like best!! Best all out speed was the -2in Imco's but the Best Handleing was the -2in Merc. sportmasters...

I'd love to try a set of the newer LS small Blocks in my boat!! With the power they make and how light they are it would be AWESOME!!:eek:

Just joking, that was the time I remember, I was working with Trent, and we were having drive issues also.