Converting Standard 4.3 to Vortec. Is it worth it?

[jserr68594]

I have a 1994 Regal 20' open bow with the 4.3LX w/ 1.84 gearing. The boat has a 4 brl. carb and is rated at 180 HP. I run a 23 pitch prop and turn around 48 MPH @ 4900 RPM. I am looking to pick up more top speed. I know to get that I will need to change props due to over revving. I know I am also out of power as well though too.

How much power will I pick up by adding the Vortec heads and Edelbrock intake? With the proper prop, how much MPH will I gain? I do have the vortec heads off of a 2005 Chevy truck I can use. I have also considered a 5.7 swap as well, but that is pricey and a lot of work! I am open to any suggestions!

Thanks in advance for any input!

 

[NHGuy]

Re: Converting Standard 4.3 to Vortec. Is it worth it?

The heads are in your possession, put them on. You will get a little top end and a little mid range torque. But you'll only get a 1 to 3 mph increase in speed.
A 5.7, sure. But as you are aware, there is much more money needed to do that. Hard decision. Doing it right would call for a different ratio in your drive too.

 

[Howard Sterndrive]

Re: Converting Standard 4.3 to Vortec. Is it worth it?

I run a 23 pitch prop and turn around 48 MPH @ 4900 RPM.

stainless prop?

if not, that's where you want to spend the money and feel a significant return

 

[dollarten]

Re: Converting Standard 4.3 to Vortec. Is it worth it?

The stainless prop gets my vote too

stainless prop?

if not, that's where you want to spend the money and feel a significant return

 

[achris]

Re: Converting Standard 4.3 to Vortec. Is it worth it?

With the 23" prop you are near the top end of efficiency. If you change the top box gear set and got yourself into a 1.65:1 ratio you would run a 21" prop and that would pull the revs back to about 4750. Also vote for the SS prop.

Don't know where you are, but 42 knots is a decent amount of speed for a 20' open deck boat already. Trying to break the '1 minute mile'? My boat will do the same speed, but there is maybe 3 days a year I can use it. Most the time I'm cruising at 18-24 knots. Seems like an awful lot of work (and money) for something you can use a few times a year.

Chris......

 

[Silly Seville]

Re: Converting Standard 4.3 to Vortec. Is it worth it?

Yeah, I've never understood this "need for speed" thing when it comes to little boats. If you are truly getting 48mph GPS in a 20' bow rider...that is fast enough! I mean, where do you need to go in such a hurry that a 1-3 mph gain is going to benefit you any? I would enjoy watching you trying to go 50mph across a three foot chop! In any event, the Vortec conversion is indeed a cheap horsepower upgrade, and worthy of doing. However, if you really need to test your own mettle, install a 300hp 350 MAG and you will achieve your goal of flight over water. Just wear a crash helmet and kill switch lanyard for when you encounter the inevitable rogue wave or confused seas at that speed!

 

[Alwhite00]

Re: Converting Standard 4.3 to Vortec. Is it worth it?

Is it freshwater cooled? Is the edelbrock intake aluminum?

LK

 

[jserr68594]

Re: Converting Standard 4.3 to Vortec. Is it worth it?

I boat mostly in the Maumee River, which is usually almost like glass. You can run full throttle all day out there if you would like! The prop I have is stainless. It is a Quicksilver Power2 variable pitch prop. It starts at 17 pitch and shifts to 23 pitch at any shift point I set it at. It works very well. Here is a video of both the river and the prop in action. Watch the tach and you will see it shift. Also, the boat is freshwater cooled.

http://www.youtube.com/watch?v=jNU_E7q5TjU

If I were to do the upgrade, it would be with an aluminum Edelbrock intake. However, if the upgrade is only going to bring me two MPH, it isn't worth it to me. I do have another variable pitch prop by Land & Sea called the Torqueshift. I am in the process of rebuilding it. The prop starts at 11 pitch and ends anywhere from 20-26 pitch depending on where you set it. So that would take care of my over revving issue.

I am not going to lie, I like power and I like speed! I am in a area where I can take advantage of both. That is the only reason I have considered messing with the boat. I do also like the old saying "If it isn't broke don't fix it" though. My boat runs good, so I am probably better off leaving it be.

 

[jserr68594]

Re: Converting Standard 4.3 to Vortec. Is it worth it?

Also, if I were to upgrade to the 5.7 260HP with a 1.47 ratio gear, how would the boat run? Is there a way to caculate gains assuming I am using the same prop?

 

[achris]

Re: Converting Standard 4.3 to Vortec. Is it worth it?

Rule of squares. To double the speed you need 2 squared, 4 times the power. As a guide, I changed engine from a 4.3LX (same as yours) to a 4.3 MPI. That 180hp to 220hp, I gained 3 knots. (The change was not done for speed gain, btw). So, based on that, you might get about 5 knots increase going from 180hp to 260hp....

Chris.....

 

[machz1000]

Re: Converting Standard 4.3 to Vortec. Is it worth it?

i did the same upgrade to my 20ft i had nocetably more power through the whole rpm range and went from 47 mph before upgrade to 52mph after on gps it was well worth the upgrade in m case

 

[jserr68594]

Re: Converting Standard 4.3 to Vortec. Is it worth it?

i did the same upgrade to my 20ft i had nocetably more power through the whole rpm range and went from 47 mph before upgrade to 52mph after on gps it was well worth the upgrade in m case

That sounds promising! Did you already have a 4 brl. carb on the 4.3 before the upgrade? Did you use automotive or marine heads? What intake did you use?

Thanks!

 

[Silly Seville]

Re: Converting Standard 4.3 to Vortec. Is it worth it?

Did you use automotive or marine heads?

There is simply no such thing as "marine heads" for your V-6...or any OEM automotive based engine.

 

[90stingray]

Re: Converting Standard 4.3 to Vortec. Is it worth it?

Wow... that setup seems like you are getting the absolute max out of the package. That prop is sweet... i would leave everything as is. Seems like you have a nice holeshot and good top end. If you are for all out speed... you have the room in the rpms to go with a bigger pitch prop.

 

[achris]

Re: Converting Standard 4.3 to Vortec. Is it worth it?

Just looked at your video. Very nice... But you do seem to have quite a bit of pitch/porpoising at the higher speed. If you get the engine to push you any quicker, that is going to get way worse. But if you are out for sheer top speed, ditch the shifting prop! (very in-efficient at high speeds. You currently have 29% slip, way too much). Put a 23" Laser II on with the vent plugs removed and watch that thing pull the arms out of a skier's sockets! My calculations say with a 23" Laser II, your top revs should drop to about 4800, but your top speed will go to about 47 knots (54 MPH)...

How's them apples?

 

[machz1000]

Re: Converting Standard 4.3 to Vortec. Is it worth it?

i am running edelbrock intake and edelbrock 600 cfm marine carb heads are 1998 off a s10

 

[jserr68594]

Re: Converting Standard 4.3 to Vortec. Is it worth it?

Wouldn't I loose a whole lot down low with that prop? I had a Vortex 23P aluminum prop on it before and it was doggish coming out of the hole.

Why do you you think the shifting prop has so much slip?

 

[jserr68594]

Re: Converting Standard 4.3 to Vortec. Is it worth it?

i am running edelbrock intake and edelbrock 600 cfm marine carb heads are 1998 off a s10

Did you run into any problems with the swap? I have heard that you should change the valve springs out on the automotive heads, did you have to do this?

Was it worth the headache? Thanks for the input!

 

[achris]

Re: Converting Standard 4.3 to Vortec. Is it worth it?

Wouldn't I loose a whole lot down low with that prop? I had a Vortex 23P aluminum prop on it before and it was doggish coming out of the hole.

Why do you you think the shifting prop has so much slip?

The blade shape (particularly curve at the root) are different between a 17" and a 23". A shifting prop can't be the best for both, so it's a compromise between the 2 different pitches. The best thing you can do is to decide on the day whether you want hole-shot or top speed and fit the prop appropriate for that job.

Chris.......

 

[machz1000]

Re: Converting Standard 4.3 to Vortec. Is it worth it?

had no problems with valve float.First run of the year only had a 19pitch prop it would rev 5500 with that on it seemed to like 21 would rev 5000 ran a rebuilt 23 had a vibration in it would rev 4600-4700 boat had more speed with the 21 the motor likes 5000 rpm never checked to see how far my tach is off