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Engine swap
skidrow
Member Posts: 45 ✭✭
I have a 2004 FV 270 with the 350 mag mpi. The motor will get me up on plane in 8-9 seconds
with 2 people and full fuel. Top Speed that I can get out of it is about 36 mph at 4900 rpm fully trimmed out.
Cruise is around 3800 rpm @ 25 mph.
Looking for more power and top speed.
I'm wondering if I can swap out the motor for a big block 496 H.O. or other larger h.p. motor?
Would it fit?
Thoughts?
Thanks
Comments
I hear you and know exactly what you are talking about. I have always believed that getting (within reason) the biggest engine you can in your boat makes for a better ride that will be LESS expensive on gas in the long run! Sooo here goes, my marine dealer now only brings in the 290s with the 8.2 mag in them. I don't think there is a huge hull difference between the 270 and 290 HULL. It would be easy for any decent tech to tell you iif you can drop a 496 into your engine bay. An 8.1 (496) would be a great choice. You will also need a new drive IF you have an Alpha drive. If you have the B lll that should work as I don't think you need the X drive for a 496. Two thoughts: First - If, for some reason I am unaware of, a 496 won't fit into your engine bay, try going out in a "sister" ship with a 377 mag and see if that will do the trick. The 377 (6.2) would not pull nearly as well as a 496 but might be adequate. OR - Plan two: It might be cheaper to sell your present boat and buy the same model (or a year or two newer) with the 496. Good Luck MT BTW just thought of a third option: I had a 350 mag that I had stroked - turned it into a 383 with 390 HP. It pulled all the way from 0 rpm to 5000 rpm in a straight line, a REAL beast with huge torque. You could see what the cost of that was. It would work with a Blll drive or a Bravo1. Just another thought.
Those stats are 10% below what I get in my 270 with the very same engine, and that's 10% you really need back. I don't have any bottom paint so maybe that's the difference if you do. Is the bottom squeaky clean? Are you running a Bravo3 OD with the right props? Recent tune up? Fresh E0 fuel? Tabs fully down on start with drive fully down/fwd? I'd start there.
Would all the work/time/money and addl weight really add up to enough of a performance increase that'd give you what you ultimately want? It'd be my opinion that while you could go with an engine transplant/upgrade (especially if yours is tired/overdue/you have easy access to a new one), it might just be simpler to trade out of your 270 and get something more performance driven rather than an RV of a boat.
That's not a bad thing, and coming from a guy who also owns one. As a fact, all of these boats are a lot less "express" than they are "cruisers". She's a beast but we love ours for what she provides.
If you do upgrade I'll be interested in your outcome for the inevitable day when my 5.7 gets too tired to get it up....... on plane.
Hope that helps. Mike
Part of getting your engine HP is the luck of the draw. Mercruiser will admit that the HP of their 350 Mags (for example) is +/- 5% of the "advertised" HP. That is true for ANY mass produced marine engine (and likely automotive too) from ALL manufacturers. My engine building guru friend who built racing engines from all over N.A. said the difference is more like 8%. BTW guys, on any given day the air temperature and humidity have as much bearing on an engine's performance as load. AND then there's the altitude, which really saps an engine's ability to perform. That's before we get into hull weight. Want to guess the difference between two hulls of the same model coming off a production line that doesn't vacuum bag and heat cure their hulls but just relies on "roilling out" the resin? BIG differences. Very, very hard to compare the same boats as they really aren't, for scientific comparison purposes, the same boats at all - too many variables to compare a 5 mph difference. What you have to do, in my opinion, is decide if the boat YOU have is performing well enough for YOU and then do something about it. MT
Hi Skidrow I have a 2006 270 with a 8.1 Volvo cruise at 3600 rpm 32 mph top speed 45 at 4500 rpm wiyh 2 adults and full tank gaz full tank water
WaterWolf I bet you actually get better gas mileage with your 496 than a 350 or 377 would get because they would be working real hard when that big 496 would be loafing. MT
If someone/me did need/want a new larger displacement Merc engine I'd have to wonder:
Invest in whipple and dental floss..
Whipple for super charger, floss to clean bugs out of your teeth..
Mike with your ability and awesome shop, I'd pull my engine and take it to a builder and turn it into a 383. Some builders will swap engines and charge for the upgrades. A 383 still has decent gas mileage plus the awesome power AND torque. You could do a 377 but why stop there for about the same price? MT
It's far too clean, ry... I don't trust it..
Thanks for all the comments guys....
Yeah it's a hard choice....either spend money and upgrade to a newer
boat with bigger motor(s) or cheaper route, replace the motor.
I'm running a B3 outdrive with 2:20 ratio. Have a genset as well to weigh it down.
Running 23p props , so wot its near the top of the RPM range of 5000.
Tune up every spring and boat is clean, no paint on hull.
For my wife and I, we love the boat.
I have been looking around for direct replacement drop in motors.
Cheapest I found so far is Michigan motorz that sells 496 **** for $16500.
wondering if it will fit. Dimensions are very close to the 350 map mpi...then wiring harness etc...
hmmm .......decisions decisions
Yike$$$. That's a lot more than I thought. At that rate if mine gets sick and tired I'll pull it and have it massaged for more ponies like MT and Drew said. I'm going right home and check the oil. I can't lose that engine or it's curtains for this ride.
Skid, That's exactly what our boats setup is and I don't have any issue with how it performs.
I'm sure that new motor would fit if the motor mounts are even close. Otherwise it'd be time to glass in some new front stringers, write the big check for a repower on a 10y/o boat, buy harness, etc, etc..... I just can't imagine the payback would be worth the outlay of time/money. Good luck in your decision. Mike
Skid, what would you find suitable? Expectations? Something a few more ponies can provide or something requiring a stable?
Mike- you're on salt, I bet this explains the differences both in buoyancy and air pressure..
Steve, that would certainly do it but I think Skid can work with what he has to bump his HP or find a good used engine. I must say I do like the picture you posted of the Merc diesel. Is it a VW TDI? I guess if I want to know the cost of one of those I had better be sitting down - right? MT .....P.S. I see Defender marine now carries a number of reasonably priced in-boat diesel fuel polishing systems. Impressive.
MT you are right fellow boaters at my marina do have 5.7 and 6.2 on similar and a bit smaller boats and there performance is less and there gas milage is worst then me
All good points to think about...MT...
I'm also thinking of a supercharger...low boost with an intercooler.....
easy to install and no motor re and re..
any thoughts?
You'll be running boost all the time with the sc. I would guess your engine life would be a lot shorter plus you might have to deal with the MPI programming (I'll defer to others who know this part better than me). SC are good for low end power but become parasitic at higher rpm (like running your a/c on a car) unless you can clutch it. Diesels can run full boost all the time due to the combustion cycle.
BTW: You would have to make a water to air intercooler since you have no moving air for a traditional intercooler. You would need to use a raw water supply too, which means another thru hull, pump, strainer and an outlet. $$$$$ If it ever leaked in the heat exchanger you'd ruin your engine to boot unless you ran the water side at a negative pressure to the air in the intercooler. All doable for a cost.
Or bite the bullet and go with one of these conversions (and they can run on diesel RY!!) You can get 400+hp at about 160# of engine weight.
http://marineturbine.com/projects.asp
PC BYC, Holland, MI
I have the same boat - 2005 270 FV - but with a 6.2. My numbers are very similar to yours. Top speed is 38 at about 5000. I think I get on plane a little quicker, but not much, and it is hard for me to know when to stop the clock since it takes a little while to really level out.
I would think a 383 stroker would be the way to go. Longer stroke means more torque which is what you need to get up on plane, and no need to change your mounts or wiring. I do like the supercharger idea from drewactual.
The whipple chargers are great. As BD said you do have to reprogram the electronic set-up. This took us the longest time to do. We had to press a button every 100 rpm up the line but I think that has all changed now and become more user friendly. Again as BD siad, even at low boost there will be some shortening of engine life unless the engine has been built with supercharging in mind. Whipplecharger (a very ethical company) addresses this on their web site. I agree with JH that stroking the engine to a 383 would be a very good option. You'd keep your boat. You wouldn't have to worry about matching-up engine mounts etc. You should be able to find someone who could stroke it for a decent cost. That or a used 383 or 496 (if it'll fit). Lots to look at but hopefully all fun. MT
Steve, the 454 is no longer made for boats. However, you are 100% correct that it is one tough motor. Also, it's biggest bonus is that it is very easy to take its base HP of 330 up much highe -r safely. There should be a number of used 454's - even already marinized ones - out there. It will take Skidrow some time, but if he really wants to I think he can find a reasonably priced solution to his HP needs. MT
Here you go: http://www.usmarineengine.com/marine-454-engine-01-04.html
PC BYC, Holland, MI
I can t you RY for a first boat. it was a 1976 cc bicentennial 17ft with a 350 small block. Was great for barefoot skiing! Was my grandfather's, then passed to my dad, then I took it out every week in the summer when I was about 14.
Dream 'Inn III -- 2008 400 Express
X
ry- mpi manifolds are a plenty for the BBC's... agree w/ the EFI comment... i stepped back to a carb with this current engine (4.3), and i pretty much hate it...
megasquirt is a good stand alone program for managing fuel trim on a boosted engine, and likely the easiest and safest route.. you'll need bigger injectors and you'll need to be able to monitor exhaust o2, otherwise it's a guessing game. guessing isn't good..
if you only need a few ponies to get your expectations, you can install rocker rollers with a bit higher ratio (not enough to tap the lifter rod against the heads though!), that will net you 10~20hp... then.. you could pull intake, heads, exhaust, and port and polish them, do some bowl blend and fill work (machine shop, not too much $), enlarge intake valve face, ect... new beehive springs, one piece valve stems, thinner head gaskets to increase compression, all port matched to intake manifold and exhaust manifold... that will add another 20~30hp on top of the first 10~20hp... say you got it perfect, and added 50 ponies and manipulated your torque curve to a better range of say - 2500~5400RPM? would that suffice?
every 10cfm of air through that engine @ proper stoich ratio will net you a pony.. you can get 500cfm's through that thing with the above mods, and you can do most of them yourself for $1~1.5k or so, including machine work on the heads.
anything more will be costly... whipple=$5k or so entry.... programming and turn key install another $1~2k...
having a shop build and balance a short block/rotating assembly stroker (go short/rotating assembly, and specify camshaft, and an automotive shop can do this for you cheaper than a marine shop) and you're looking at likely $3k or so, and the beauty of that is you can put your freshened up heads, intake and exhaust mani's back on it, as well as the accessories you have now... all done for .... maybe $6k? and that stroker route could get you a benji pony pretty easily, and torque to waste.. still, though, short of s/c'ing it, you're still going to be shy of 500hp safely.. and now, you're at the limit's of your drive....
yup... I watched a dude fit a 40hp cover over a 100hp engine just to get past the TWRA, and it worked until... well, it stopped working.. it was hard to explain 50+mph on a jon boat.. :-)
Thanks for all the great info....the blower issue worries me so ...I think the
383 stroker works for the 50 added horse should do a good job and
since its drop in makes it easier...cheapest I could find so far is
$8500..will see
X
Go for the biggest you can fit and aford
350 mag
into a 383 stroker...balanced and blueprinted and will remove and install
engine...including a programmed ecm 555 to compensate for the
new build approx $8000..looks like I will use him..will wait another month before pulling boat out to do...