replace 3.0L in 19' with 350/383 @ 400hp?

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i have a 19' bayliner capri 1952, with the merc 3.0L inline-4 @ 130hp and alpha drive.
gear ratio is 2-1 and I run a 14x21 prop and the boat will do 43-45mph on a good day with low weight @ 4900-5000 rpm.

thinking of dropping in either (a) a 350 @ 300-350hp and (b) a 383 @ ~400hp. I would most likely scrounge a 350 block and build it myself going from parts & builds published by chevy hiperf and gmhtp so the hp #'s should be fairly accurate. So, toss around outdrive ratios and prop pitches, humor me with what kind of speed you think I could get and what problems I would have.
 
1] will the drive handle the power?
2] will the engine fit under the engine cover?
3] what about the exhaust manifolds,motor mounts ,waterpump,a marine carb,feul pump backfire arrester drive line?
4]will the increase in the consumption of gas matter?
5]how much will the gears cost to change in the drive unit if available
6] how much for the new prop and instead of an aluminum prop will a stainless prop be needed with the increased horse power?
7] there are boat tests that include the mph and gph on line that would be the best idea to get an idea the performance increase .
8] will the hull take the horsepower and speed ?
 
I don't know if they came with V-8s, 400HP might be pushing beyond what the hull can handle.

Stress unpredictible, handling etc. Can the drive take the horsepower etc.
 
1) yeah probably, it's standard on the 5.7L for the past 20 years.
2) no
3) buy a set, scrounge and make a set, no brainer, regular carb (and fuel line) just to tick everybody off, no brainer, last of my concerns, what u mean about drive line?
4) no
5) couple hundred not including proper tools to put them in last i checked/remember, might just buy whole new drive.
6) $300, no not "needed" at least initially.
7) super
8) well if it don't i throttle back

boat dealer- don't have one don't want one and last one I think told one to g.f.t. they are worthless. I know i'm looking at around 311 lb increase going off the advertised weights of 635 and 946 for the 3.0L/5.7L at merc website. I can run the boat now with 2 guys sitting at the transom which is +350-400 lbs and boat runs fine minus the extra few seconds to plane.

i wouldn't bring this up if I already didn't look into it and know for the most part it will fit minus little things. Biggest things are motor mounts which I can fab up and bolt to the stringers, the original engine box is just plywood covered in carpet and vinyl. I have to find out for sure unless someone knows the dimensions are all common that the bellhousing of a 5.7L will will bolt up to the transom assembly of the 3.0L. And there's the exhaust downpipes which i also hope are common and will bolt to the transom assembly, so from there it's just getting a set of exh manifolds which hopefully just bolt up.
 
Be sure you are wearing your life jacket when you get that thing up to about 60.
 
Not sure a gen I Alpha or the Bayliner hull structure can reliably put up with that much HP.

Especially this season, why are you increasing fuel use? 45 is pretty fast already if you're not racing.

A 4.3 is a better upgrade within the framework of what you already have.
 
my dad has a 1987 21 foot cobalt, the thing ways like 3600 pounds. Any ways with a 350 rates at 250 hp it still gets up and goes at like 50 to 51. So um yeah a 400 hp 19 ft bayliner would be a bit crazy unless you want to race or something.
 
The 350 block gets that small gear case yet today.
There have been upgrades inside the Merc drive in the last twenty.
The problem is the horsepower.
Lower rated 350s get that small gear case. A hopped up engine is another matter.
The gear ratios would be a good deal different as well.
Dealer should have a chart for prop size/pitch for the bigger motor if you insist.
Be prepared for bearing and drive shaft failure.
 
Originally Posted By: FZ1
Be sure you are wearing your life jacket when you get that thing up to about 60.


ok mom, thanks
 
Ahhh, the never ending thinking of "more power." Boating is the one thing that if you want more speed, it's going to cost you. My dad had a plaque on his 30 footer that says "a boat is nothing but a hole in the water from which one pours money." That has been so true to me.
First, not just the engine concerns, but have to change out the whole cooling system. You'll need to water exhaust manifolds, expensive, a U tube to collect both sides that then dump into the outdrive. You could go with through the hull exhaust, but that is loud and a lot of marianas have regulations against that. Your older gen I system will not handle the torque. They are good up to about 275. You'll shear the gears right off the outdrive. Then, you'll have to get a new engine management system. This is only the start.
 
Originally Posted By: oilboy123
Put the 400HP in a flat bottom drag boat.
You will want way more horsepower than 400 in a flatbottom ,that is sissy horsepower.
 
Originally Posted By: 1 FMF
Originally Posted By: FZ1
Be sure you are wearing your life jacket when you get that thing up to about 60.


ok mom, thanks
Just trying to keep you out of the trouble you usually get yourself into. Luv,Mom.
 
Originally Posted By: Schmoe

First, not just the engine concerns, but have to change out the whole cooling system. You'll need to water exhaust manifolds, expensive, a U tube to collect both sides that then dump into the outdrive. You could go with through the hull exhaust, but that is loud and a lot of marianas have regulations against that. Your older gen I system will not handle the torque. They are good up to about 275. You'll shear the gears right off the outdrive. Then, you'll have to get a new engine management system. This is only the start.


current engine is raw water cooled, whatever i drop in is also going to be raw water cooled.

engine management system.. what are you talking about? carb & distributor... like it's been done for the past 40 yrs.

shear the gears right off eh? like, as soon as I start the thing or put it in gear?
 
With all the cautions posted ..... I would say in the spirit of hot rodding and more power do it and keep us informed on the progress. I would like to add and this is so important, the problem with boats is the exhaust .The log type manifolds choke the power and you will never realize the power available in the higher rpms. I have messed around over the years with flat bottom drag boats and run wet log style manifolds and headers on the same engine and the loss of power is incredable . I would build a low end torque motor . Also you will want to with a covered motor run a marine carb, it is modified to not leak gas through the throttle shaft and the float bowl breathers are shaped to drain the feul into the carb if a float gets stuck.I think the alt and starter are marinized for explosion/fire safty also.
 
Steve is correct.
The marine carb may be jetted a bit richer as well.
Hi flow exhaust manifolds are available(water cooled) from
Marine high performance divisions: MercMarine Racing for example.
But take your credit cards along; they are very pricy.
 
Originally Posted By: 1 FMF


current engine is raw water cooled, whatever i drop in is also going to be raw water cooled.


Why would ANYONE dump high dollars into a marine grade racing powertrain and then pump seawater through it? Do it right and run FWC.

BOAT. Break Out Another Thousand.
 
Not when you put it in gear and the dog clutches activate, I'm talking screaming down the water when you reach peak HP and high torque. Engine management, well I was refering to a Mercruiser setup. If your just going to do a drop in and wire it up yourself, then maybe you can get by with it. Your also going to have to change out your throw shifter and kill switch, I think. Haven't really put a lot of thought into that kind of setup when I realized the cost involved on doing that to my 3.0LX setup on my 19 footer. Just not worth the money to be King of the Lake, especially now with gas running 4.30 at the docks.
Good point on the carbs, they do run a lot richer than the automotive version. Never failed that some customers would come in and complain that the engine is burning oil by looking at the exhaust port inside the prop. Even though they checked the oil themselves and said that the dip stick level hadn't moved any.
 
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Since the 1952 is only offered with the 3.0 the fiberglass layup schedule will be light. Models offered with various engines have a stronger layup schedule for the larger engines. Bracing the stringers near the stern would be a priority in my book. The alpha drive (depending on year) is supposedly good for 300 propshaft horsepower.
 
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