4.3l to 5.7l swap ?'s

[Bergerson]

Hi all, I have been reading these forums for hours and hours on end, usually I come here to find answers and a little searching and I never even need to ask a ?. for the most part I see that this swap has been done a few times and some agree with the swap and some don't, I have a 1990 chaperall 1900 19' with the 4.3l in it and a alpha I outdrive , I am wanting more power and tourque, the boat does great with only one or two people in it but any more than that and trying to pull waterskiers up, and or haul butt to our favorite fishing spot it has trouble in the power department. I know I will need to change the outdrive to the 1.5 ratio, but I just want some honest opinions if this would be worth my while to do? I have located a low hour 1997 5.7l with alpha one genII outdrive for $2000.00 I should be able to sell my 4.3l with outdrive for close to the same shouldnt I? just wondering how much work the motor mounts are going to be and if anyone makes any adapter plates/mounts that would use the 4.3l's motor mounts. thank you for your time!

 

[180shabah]

Re: 4.3l to 5.7l swap ?'s

If you can get a complete setup in good conition for that price - I'd do it. If you are swapping everything it is simple.

That is going to be a huge jump in power, so be ready for some tricky handling. May not do anything scary, but it could, just be ready for it.

 

[Bergerson]

Re: 4.3l to 5.7l swap ?'s

bump

 

[danond]

Re: 4.3l to 5.7l swap ?'s

There are no adapter plates. I'm not sure how the engine mounts line up, but the fiberglass work wouldn't be a big deal if you had to move some things around.

It's up to you, dude. The swap will net more power, but not a huge amount.

There won't be a handling issue. A 19' boat will handle a 350 no problem. Plenty of them made with that size engine in them.

 

[TilliamWe]

Re: 4.3l to 5.7l swap ?'s

Making front motor mounts is EASY. You unscrew the mounts already in your stringers, and move them forward about 4.4 inches. And the mounts that are bolted to the engines should be exactly the same.
The other thing to check is clearance in the front of your bilge. When my father put a 5.7 in a 19' Sea Ray that had a 4.3, the fuel tank and some of its lines were in the way.
It will not turn your boat into a rocket, but it would help. Chaparrals are usually a little heavy for their size, and a 19'er should handle a 5.7, no problem. And i know others will freak out, but you could get by without changing your 1.81 ratio drive, if you had a high enough pitch propeller. My dad was able to use a 25 pitch prop on his SeaRay after the change to the 5.7.
But if you are buying a complete engine/drive, then it should have a 1.47. $2000 is a really good price on a complete engine/drive. Does it have a lot of hours or other problems?

 

[180shabah]

Re: 4.3l to 5.7l swap ?'s

The swap will net more power, but not a huge amount.

Beg to differ. his current 4.3 is pre vortec so we have a power range of 155hp to 185hp at the prop. The 5.7 is from '97 so it most likely(although it might not) has vortec heads, so the ratings will range from 250-290hp at the prop.

Now we don't know the power of the existing engine OR the new one but the difference will be between 65hp and 135hp at the prop. 65hp in a 19' boat is very noticable, 135hp is HUGE no matter how you slice it.

For the install - rear mounts are irrelevent, you are getting the drive with it. Front mounts are just screwed into the stringers. As stated above, pull them out, move them forward, screw them back in.

What are the powers ratings of the two engines?

 

[Rat Capri]

Re: 4.3l to 5.7l swap ?'s

The 5.7 is from '97 so it most likely(although it might not) has vortec heads, so the ratings will range from 250-290hp at the prop.

that would be crank rating, not prop

 

[mkast]

Re: 4.3l to 5.7l swap ?'s

If you in fact acquire a complete 350/Alpha power package, the swap is simple. Label anything you touch with a decent label, by the time you get back to it the writing disappears.
Some engine mounts are glassed in, some aren't. Suspend the engine with the rear mounts installed, insert the alignment bar, move the engine on the hoist until the engine is aligned , use a plumb bob to mark the location of the
engine mounts, install the front mounts, either bolt or glass.

 

[180shabah]

Re: 4.3l to 5.7l swap ?'s

that would be crank rating, not prop

Since the early '90s, all ratings have been at the prop. Prior to that, the prop rating was optional and most manufacturers listed the crank rating because it was obviously higher(30hp difference with Mercruiser).

There were alot of confused people when this happened.

4.3s dropped to 155 and 175
5.7s dropped to 210 and 230

Then the vortecs were introduced and 2bbl 4.3s and 5.7s went up to 190 and 250 - but still rated at the prop.

 

[dave1989]

Re: 4.3l to 5.7l swap ?'s

I just completed the same swap. A 1989 20' sea ray 4.3 to 5.7. While I am still ironing out some kinks, the motor is fantastic in my boat. I can run cruising speeds without feeling like I am running the motor to death the added torgue feels great. As for the moving the front mounts, I was doing a stringer and deck replacement so it was not that big of a deal. I would go for it.

 

[wca_tim]

Re: 4.3l to 5.7l swap ?'s

I did it last year in a 17 ft checkmate. a couple of things. movoing the front mounts is straightforward... and most everything else should just about bolt right up.

Even if the engine combo you're getting has a set of exhaust manifolds, I would probably leave room in the budget for new manifolds and risers.

I'm going to disagree with a number of other folks on the gear ratio. I am running a 1.81 gear ratio (stock 4.3 gear ratio) even though I have a 1.5 ratio upper in the garage (and have run it). I'm guessing based on the limited info that you're running somewhere in the neighborhood what? a 19 or 21 pitch prop right now if that. If you assume you pick up enough power to add something like 10 mph on the top end (and a lot of accelleration, etc.. below wot), then you're probalby going to wind up running something from 23-27 pitch after it's all said and done... there are a number of GREAT performing reasily available 3 and 4 bladed props in that pitch range.

Don't let anyone fool you, even though it is not a huge amount of weight difference, it will make a difference in handling. Mainly just a good bit of extra weight in the azz end of the boat. shouldn't create any real handling problems though...

 

[Bergerson]

Re: 4.3l to 5.7l swap ?'s

Making front motor mounts is EASY. You unscrew the mounts already in your stringers, and move them forward about 4.4 inches. And the mounts that are bolted to the engines should be exactly the same.
The other thing to check is clearance in the front of your bilge. When my father put a 5.7 in a 19' Sea Ray that had a 4.3, the fuel tank and some of its lines were in the way.
It will not turn your boat into a rocket, but it would help. Chaparrals are usually a little heavy for their size, and a 19'er should handle a 5.7, no problem. And i know others will freak out, but you could get by without changing your 1.81 ratio drive, if you had a high enough pitch propeller. My dad was able to use a 25 pitch prop on his SeaRay after the change to the 5.7.
But if you are buying a complete engine/drive, then it should have a 1.47. $2000 is a really good price on a complete engine/drive. Does it have a lot of hours or other problems?

No Problems with the motor or drive, it only has 174 hours on it, the boat was totaled by the ins co. when it fell off the trailer at the boat launch!

What are the powers ratings of the two engines?

my 4.3l is rated at 175hp, I put on the vortec heads,intake and a 600cfm carb. so around 190 I am guessing, the 5.7 is a vortec and is rated at 250, but with a upgraded intake and a 750cfm carb its prob just a little more than that.


Thank you all for your input and help.

 

[Bergerson]

Re: 4.3l to 5.7l swap ?'s

I did it last year in a 17 ft checkmate. a couple of things. movoing the front mounts is straightforward... and most everything else should just about bolt right up.

Even if the engine combo you're getting has a set of exhaust manifolds, I would probably leave room in the budget for new manifolds and risers.

I'm going to disagree with a number of other folks on the gear ratio. I am running a 1.81 gear ratio (stock 4.3 gear ratio) even though I have a 1.5 ratio upper in the garage (and have run it). I'm guessing based on the limited info that you're running somewhere in the neighborhood what? a 19 or 21 pitch prop right now if that. If you assume you pick up enough power to add something like 10 mph on the top end (and a lot of accelleration, etc.. below wot), then you're probalby going to wind up running something from 23-27 pitch after it's all said and done... there are a number of GREAT performing reasily available 3 and 4 bladed props in that pitch range.

Don't let anyone fool you, even though it is not a huge amount of weight difference, it will make a difference in handling. Mainly just a good bit of extra weight in the azz end of the boat. shouldn't create any real handling problems though...

I am running a Quicksilver Power2 2 speed prop that is 17p-23p, I am only able to maintain 4350 rpm, at wot with 2-3 people in the boat, 52mph top speed, but add a couple adults and gear and my 4350 goes down to about 4100, so does speed and i hate running it wot all the time just to get cruising or up on a plane in a reasnoable ammount of time. I am guessing I will run the same prop with the 5.7 or have it re-pitched one or two inches if needed. thanks for the help

 

[wca_tim]

Re: 4.3l to 5.7l swap ?'s

I am running a Quicksilver Power2 2 speed prop that is 17p-23p, I am only able to maintain 4350 rpm, at wot with 2-3 people in the boat, 52mph top speed, but add a couple adults and gear and my 4350 goes down to about 4100, so does speed and i hate running it wot all the time just to get cruising or up on a plane in a reasnoable ammount of time. I am guessing I will run the same prop with the 5.7 or have it re-pitched one or two inches if needed. thanks for the help

I'm assuming that your 52 mph is by the speedometer - otherwise something is wrong. at that rpm mid 40's is much more realistic.

your current wot is way too low, the 23" prop you're running on top end is way too much for your set up the way it is. It needs more like a 20 - 21 now.

If you do the swap, I would be really surprised if you have enough gain to run a 23 " prop with a stock 350 and a 1.47 gear ratio... You would probably be able to run the prop you have now with the current 1.81 outdrive behind a 350..

To turn the prop you have now with a 1.47 gear ratio at wot 4800 rpms, you're talking a 20 mph gain. That'll take a good bit more than a step up to a stock 350...

 

[mkast]

Re: 4.3l to 5.7l swap ?'s

I am running a Quicksilver Power2 2 speed prop that is 17p-23p, I am guessing I will run the same prop with the 5.7 or have it re-pitched one or two inches if needed. thanks for the help

The weights inside your propeller have a number stamped on them, that's the pitch your prop is. If you want to change the pitch, you have to change the weights, all the blades, 19, 21 or 23 are the same.

 

[dontask]

Re: 4.3l to 5.7l swap ?'s

I would not swap motors. Not worth the headaches. If you don't need top end, drop the prop pitch by 2". Also find a good "out of the hole prop". You may need to find a prop that slips more out of the hole to get the revs of the engine where its producing better horse power. Ck out why people have drilled their props (not for the novice). Obviously don't over rev the engine when going for speed. If your worried about over revs ck out "rev limiters" if your engine does not have one already. Tune the engine, make sure its putting out the horse power it originally was built for. If needing more horse power (after the engine is tuned up) and you don't want to drop prop pitch & design ck out a different intake manifold and carb. I'm running a 4.3 Alpha 1 on a 19 ft rated 9 passenger br right now and I'm having no power problems under normal loads. I did swap props for what I normally do with the boat though and I don't run at top end.
Second option - Have 2 different design props to accomplish what your planning to do that day. One for speeding to your favorite fishing spot and one for bottom end pull when your wanting to ski. Keep both props on the boat along with a $10 prop wrench. The prop your not using that day can be the emergency back up prop if needed. This 5 minute prop exchange sure beats a 2 day expensive engine exchange your thinking about doing .

 

[Bergerson]

Re: 4.3l to 5.7l swap ?'s

The weights inside your propeller have a number stamped on them, that's the pitch your prop is. If you want to change the pitch, you have to change the weights, all the blades, 19, 21 or 23 are the same.

Do you know where i can obtain these weights? I was thinking I could still just have the blades worked over???

 

[wca_tim]

Re: 4.3l to 5.7l swap ?'s

I might see if you can find a 19" 4 blade or a 21" vented prop to try. I'm guessing that with a good 19" 4-blade you'll lose 4-5 mph on the top end, but it'll feel like you put a bigger engine in it in terms of accelleration, planing, etc... I bet compared to now it would literally leap onto a plane. Lots cheaper and a lot less headache to at least try. Lots of the boat shops here keep a stash of used props that you might be able to "try" a couple of with a deposit - especially if you're a good customer and aren't a butt to them (not saying you are, but you ever see how some people act like jerks and then get mad when people won't be helpful??).

I wouldn't drill the blades, nor hub yourself, biut if you want a vented prop buy one of the merc series that comes drilled for plastic inserts. You can either use the solid plugs or one of three sizes to vary the amount of slip you create on takeoff...

 

[Bergerson]

Re: 4.3l to 5.7l swap ?'s

I'm assuming that your 52 mph is by the speedometer - otherwise something is wrong. at that rpm mid 40's is much more realistic.

your current wot is way too low, the 23" prop you're running on top end is way too much for your set up the way it is. It needs more like a 20 - 21 now.

If you do the swap, I would be really surprised if you have enough gain to run a 23 " prop with a stock 350 and a 1.47 gear ratio... You would probably be able to run the prop you have now with the current 1.81 outdrive behind a 350..

To turn the prop you have now with a 1.47 gear ratio at wot 4800 rpms, you're talking a 20 mph gain. That'll take a good bit more than a step up to a stock 350...

Just asking a ? the boat the 5.7 is comming out of was a 20' wakesetter, I personally rode in this boat many times, he is running a 4 blade 23" SS Quicksilver, and is able to maintain 5k wot with that prop, I dont know the speed but it is fast, spedo says 60, but we all know that is just a guess... so you dont think i can run the 3 blade 23" on the same setup? I am really hpoing to keep the power2 prop, I love the shift from 17p to 23p feels like a two speed tranny behind the motor, on my 4.3l i am obviously able to redline the motor starting on the 17p if i want to, it jumps great out of the hole unless i am loaded down with people and pulling a skier, but i dont have the power to run that prop at 23p, like i said i can only get 4350-4400 rpm at wot. i figured the added power of the 350. would be able to run it out to 4800-5000 with the 1.5 outdrive, this motor does have a rpm performer intake, mild cam, beehive springs in the head to occomidate the extra lift in the cam and a 750 4-barrel carb, I know when he did these upgrades to the engine it netted him some HP, that you could feel in the seat of the pants when in the boat. I just want to get all of this right the first time. I am bound and determined to drop this 5.7 in my boat. it just flat out hauled *** in his boat and its like comparing a VW with a viper, when we were out on the water, he would leave me in his wake with no problems anytime he wanted with little effort. Thanks again for all of your guys replies!!

 

[mkast]

Re: 4.3l to 5.7l swap ?'s

Do not get upset, I have to ask.
You are adjusting the propeller when the load (the number of people on board) changes, aren't you?