Need improved holeshot on 95 Baja 208

[Boatman296]

Sooo I bought a $1,500 "fixer upper" 18' Baja with a 4.3 a month ago as a winter project. Two weeks later I noticed a very nice 21' 1995 Baja 208 with a 350 Mag at a local auction repo lot. As of 2 days ago, I now own two boats! My wife couldn't comprehend why I bought one when I already had the other. The reason why is because the 21 footer has captain call exhaust, very clean gel coat, good interior and we were able to use it yesterday instead of next May.

The boat fired right up after having set for a while. After richening up the carb a bit, it got on plane a faster. I would still like a bit more hole shot since I like to slalom. The boat has a SS 21 pitch prop and went 58-60 on the speedo at 4900-5000 rpm. I would like to stick with the current prop for the top end (plus it has a prop lock nut on it and the key didn't come with the boat). I have read that smart tabs really help with getting on plane. Those would probably be my first option. I have also read that Vortec heads flow a better on the 350's. I am not sure if this boat has a stock cam.

My questions--

Would Vortecs help with low end hp and torque or would they kill it? I assume a bit of performance will also be gained from the necessary aftermarket Vortec compatible intake upgrade.

Will in need to go up in carb size from stock if I use the Vortecs? It has the original Carter.

How good are the Carter's vs a marine Holley with vac secondaries?

Thanks in advance for your thoughts.

 

[HT32BSX115]

Re: Need improved holeshot on 95 Baja 208

My questions--

Would Vortecs help with low end hp and torque or would they kill it? I assume a bit of performance will also be gained from the necessary aftermarket Vortec compatible intake upgrade.

Will in need to go up in carb size from stock if I use the Vortecs? It has the original Carter.

How good are the Carter's vs a marine Holley with vac secondaries?

Thanks in advance for your thoughts.

Howdy,

You have the optimum prop already on that engine/drive combo....if you're getting 60mph at max rated RPM....

Adding different heads will at most give you maybe a 20 hp gain at max RPM. You said you wanted better hole shot and that is not something that comes with upper RPM HP increases but comes with torque increases.

Your boat is probably not that different in size/wt from my Liberator. When I had the single prop 460 (340hp) King Cobra in it, it was pretty fast (60mph at 5000 rpm) but pretty slow out of the hole.....That was with the Bennett Sport tabs all the way down too....

When I put the same HP (330) 454 and Bravo III in it, there was a HUGE increase in hole shot and a slight reduction in top speed (about 3 mph or so but I don't care)

Your hole shot is more related to torque and prop slip than total HP at top end.

If you want more hole shot your best bet is probably a 454......I don't think spending time & money on heads and a carb will make enough difference to satisfy you.

You'll probably also be happier with cockpit adjustable tabs instead of spring loaded fixed tabs...

Your mileage may vary...


Regards,


Rick

 

[Boatman296]

Re: Need improved holeshot on 95 Baja 208

Rick and Bubba,

Thanks for the input. I totally agree that I need to focus on low rpm torque and not max rpm hp. I am wondering if the Vortec's improved chamber provides better low end torque vs the stock heads. I've read that they have great mid-lift flow but I don't know how this translates into low end torque.

The hole shot isn't bad enough that I would swap the motor out for a BB but I would like to quicken things up just a bit. I've also looked at aftermarket aluminum heads but most of their torque data starts at 2,500-3,000 rpm. I would like to see some off-idle numbers that would better reflect use in a boat.

In the end, it would probably be helpful to know the specs on the cam. If it is a higher rpm marine cam, the boat may benefit from a proper cam swap.

Jeremy

 

[wca_tim]

Re: Need improved holeshot on 95 Baja 208

Cool on the other boat!

Torque is torque, radial force, horsepower is torqe times rpms.

torque changes with gear ratio and the effective torque you can apply to the water to move forward (as in hole shot) is changed by prop pictch.

While a better set of heads will most likely give you a bit of increase in both peak torque and peak horsepower, it may or may not give any benefit down where you want to keep from drowing while tring to get up on your narrow backed slalom ski (I love to slalom).

There are a couple of things that I would try before adding heads etc... if you add some more horsepower, you'll be able to prop up t oget your wot rpms in the right place and will go faster as a result... and get the same off the line problem right back again - unless you underprop to get the holeshot back and overrev at wot if you let it run out.

two easy options in my opinoin (will still apply if you add horsepower, gain speed and increase pitch to make top end use of the extra horsepower). Neither is an engine mod.

1. pick up a good vented prop and add progressively larger vents to induce cavitation / prop slip when you put the hammer down. If you go with a merc prop they come drilled and you can buy the plastic inserts to change the size of the vent holes. Acts very much like a stall converter in your street rod and gets the rpms up to where torque is higher right away and can make a dramatic impact on your holsehot. I would try this first for all around performance and then option 2 if it's not enough to suit your taste. What 21" prop do you have?

2. I simply carry two props. ideally a good 4 blade, can be fairly cheap like a solas titan (worked great on my boat) in a 19". You'll lose some top end with that one on, but it'll hook up and pull like a train out of the hole and be better for a boat full of people. Then when you're out on your own or with just a couple people and want to fly, take 3 min and put the faster 21" back on. I lost about 4-5 mph going from a 23" laser 2 to a 21" solas titan 4, but the the holeshot and smoothness for skiing, etc... was great. (that was when had a 4.3 in the boat).


Those are things that have worked for me... neither preclude you from a big step up in horsepower later, like after the season is over for the year...

Thumbs up on the tabs. smarttabs work fine, get the stainless ones...

 

[John_S]

Re: Need improved holeshot on 95 Baja 208

"(Cam is a certainty and lifters almost a certainty. One thing is absolutely certain. $$$$$ )"

Vortec heads do not require any special cam. If engine has the stock marine (flat or roller) it will work fine with vortec heads. If it has a non-stock cam, valve clearance will need to be checked. Stock vortec heads can not take that much lift.

BTW, a '95 350 Mag has the high likelyhood that it has the stock roller cam, ie the same one used latter in all Mercruiser SBCs, including ones with vortec heads.


Note: Remove that prop lock now vs when it becomes a "need to".

 

[Boatman296]

Re: Need improved holeshot on 95 Baja 208

Thanks for all the input. It's funny, I just came from outside where I was assessing the best way to get the prop lock off. I think I might be able to take a cutting wheel and notch the ring that surrounds the lock nut. Then I can take a chisel and chip the ring away. I will have to be very careful not to damage the hub or the shaft threads.

Once the prop is off, I will try a 14.5 X 18 four blade that was gathering dust in my garage. This unit came off a boat I had a few years ago. It should bump me down to 50 mph according to the prop calculator. No biggie, I will just have to watch the revs. I am also planning on buying a set of smart tabs tomorrow. Between the prop and the tabs, I'm hoping my boat will come out of the hole a lot better. I was drowning on the slalom today.

If I still have a need for hole shot speed, then I will look at engine mods when the budget allows.

 

[HT32BSX115]

Re: Need improved holeshot on 95 Baja 208

I changed the engine and drive in my Liberator.

But I also changed from a single prop drive to a "duo-prop" drive too...

My brother, who bought the boat new, told me that the boat "hole-shots" more than twice as good as it ever did even when it was new. Same HP.

Hole shot is VERY related to prop slip, which is FAR LESS with a twin-prop counter-rotating system like the VP Duo-prop/Bravo III system...


Before, with the 460 King Cobra drive, it was a "dog" outta the hole....with the Bravo III it just ROCKETS out of the hole.....