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Formula/Thunderbird
 BoatUS Boat Groups/Manufacturer Forums>>Formula/Thunderbird
Subject Topic: Mercruiser 233 Ungrade? Post ReplyPost New Topic
 
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26SC
"Seaman Recruit"




Joined: September 08 2005
Posts: 5
Posted: September 08 2005 at 00:00 | IP Logged Quote 26SC

Does anyone know if a ford 351 can be conveted from 2bbl carb (233hp) to 4bbl (255 hp) ?
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233 Double E
"Deckhand"




Joined: May 05 2004
Posts: 116
Posted: September 08 2005 at 00:00 | IP Logged Quote 233 Double E

26SC,

Welcome on!  Glad you're here.  You're in good company on this board. 

Do I understand that you now have 2 Formula units?  ...a 26 and a 233?

The 233 is the SC model?

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26SC
"Seaman Recruit"




Joined: September 08 2005
Posts: 5
Posted: September 08 2005 at 00:00 | IP Logged Quote 26SC

Hello,

I only have a 26SC. It has twin 233 Mercs (Ford's)

Your boat is a beauty!

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233 Double E
"Deckhand"




Joined: May 05 2004
Posts: 116
Posted: September 08 2005 at 00:00 | IP Logged Quote 233 Double E

Thanks!  Cuda thinks I need to lower the Captain Ahab bow rail unless I'm using the harpoon but I'm still making mistakes and it's a handy thing to have and easy to get the rope under when anchoring.

So the 26SC has the raised cuddy area that you can stand up in right?

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26SC
"Seaman Recruit"




Joined: September 08 2005
Posts: 5
Posted: September 08 2005 at 00:00 | IP Logged Quote 26SC

Yes, it has a stand up head and a decent amount of room inside. It is 9'6" wide and has a huge cockpit. It still has great lines despite the size (i think anyway..)

I'd like to beef up th engines since I probably will replace them

This is a solid Formula.

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233 Double E
"Deckhand"




Joined: May 05 2004
Posts: 116
Posted: September 08 2005 at 00:00 | IP Logged Quote 233 Double E

I think you're the first on the board with that expanded cuddy model (forgive me if I overlooked another...)

The Vintage Formula section at the OEM site shows a 233SC model and I've always wanted to see one oer one like it on this forum or visit someone's.

I'd imagine that a 2 to 4bbl is a typical carb switch.  I have the Rochester Quadrajet 4bbl unit that came originally on mine (the orig owner later put on a Holley and sold the Rochester with the boat as a backup)  The Rochester was working when he took it off but it has not been used in a few years.  If it turns out that the Rochester unit will work on yours, It's yours for cheap.

I have the 350ci engine though so it may not be of any use on the Ford.

Maybe Fintage can be of assistance?

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74Formula233
"Seaman"




Joined: April 01 2004
Posts: 73
Posted: October 06 2005 at 00:00 | IP Logged Quote 74Formula233

It probably is not as simple as "just" a carb switch.....

The 255 probably has a more aggressive cam (slightly), and possibly slightly larger intake valves.

Remember, you have to be able to handle the extra intake air properly or you could end up with a poorly running/performing motor.

For example.....

The 302 2-BBL version of my motor was rated 188HP and I think also 215HP was another.

Mine is 225HP.  Mine is 4-BBL.  HOWEVER, mine ALSO is the only 302 of the "line-up" that has a different (more aggressive) cam than the others, as well as the only one that has 351W Heads, with larger valves.

So, going from a 2-BBL to a 4-BBL is not necessarily a good idea in-and-of-itself....you need to address the rest (cam, intake, exhaust, etc components) or your engine will most likely run like crap.

What I DID do is go from the Factory 450 cfm Holley to a 600 cfm, simply because the 450's are hard to find, and also VERY expensive!  The 600 is the same setup, but much more common, therefore, much less costly.

And, I did pick up a few hundred RPM's on the top end, but remember, I was already 4-BBL, so the increase in cfm (only 150) was much easier for the motor to handle/adjust to.

Remember, boat engines are run at high rpm's, they are MUCH more sensitive to things like Timing, etc, or they will not last long.  In fact, timing MUST be adjusted to factory spec or you will likely shorten your valve life.  It's not as wise to start playing around with a boat motor's intended design as it is an automobile engine.

Whatever you decide to do, just make sure you thoroughly research your motor's specs and consult some GOOD marine mechanics first.




Edited by Sonja Lowe on September 20 2013 at 18:00
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truckerbob
"Seaman Recruit"




Joined: November 20 2005
Posts: 2
Posted: November 21 2005 at 00:00 | IP Logged Quote truckerbob

It is as simple as changing the carb and manifold. Although you should check with a few marine mechanics to get opinions on carb models for marine use.

 If it was for a car I would say Holley 750 dual feed. It is a great carb to compliment a 351. It gives the engine an excellent acceleration curve.

 A boat has less need for take-off power and more need for sustained power (much like a pickup pulling a trailer on the highway). You will not have the low rpm surges that a vehicle has when shifting, the engine will achieve a higher rpm quickly and need the hp at that rpm.

 I highly suggest that you get the opinion of 5-6 mechanics and base your choice on those

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74Formula233
"Seaman"




Joined: April 01 2004
Posts: 73
Posted: November 21 2005 at 00:00 | IP Logged Quote 74Formula233

truckerbob,

All due respect, changing the carb/manifold on a 233HP 351W to "make it" a 255HP 351W is not a simple swap UNLESS you find out that he cams and heads are exactly the same.  If they are not, you could wind up with a poorly performing motor.

And as far as less need for take-off power?  You have that backwards.  Take-off power is even MORE important in a boat motor than a car......sustained power is easy, once the boat is on plane.  Torque is more important in a boat than HP (why do you think diesels are used on larger boats?).  Which is why you could really wind up with a poorly performing motor by adding a bunch of fuel when the cam/valves/heads can't handle it properly.

Remember, a boat is run at 3,000+ RPMs for sustained periods of time, a car is not.....boat motors generate a LOT of heat, as a result, and the valvetrain is what always "goes" first.  Throw off your balance of fuel/intake, you're waiting for trouble. 

Same goes for timing.  NEVER tweak your timing out of factory recommended range, like you can in a car.  Boat motors need to be set to what they call for.

26SC, I have a factory '73 manual that likely lists all specs for both the 233 and 255 versions of the 351W, I will look at the cam, lifter, valve specs, etc to see if a "simple" carb/manifold swap is appropriate in this case.  (It was NOT appropriate in the 302's, due to my 302 having different heads (351W heads), and different cam than the 2BBL 302!!!)

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26SC
"Seaman Recruit"




Joined: September 08 2005
Posts: 5
Posted: November 21 2005 at 00:00 | IP Logged Quote 26SC

Thanks very much. I think I'll wait to th engines crap out and upgrade, maybe to big blocks if they will fit.

By the way I had a 76 233 in 1982. Great boat.

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Bound4River
"Seaman Recruit"




Joined: November 28 2005
Posts: 6
Posted: December 03 2005 at 00:00 | IP Logged Quote Bound4River

I would like to do a carb swap also from a 2-4 bbl. Can it be done and who has the good prices?

__________________
1973 Formula Thunderbird 18'
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74Formula233
"Seaman"




Joined: April 01 2004
Posts: 73
Posted: December 08 2005 at 00:00 | IP Logged Quote 74Formula233

26SC wrote:

Thanks very much. I think I'll wait to th engines crap out and upgrade, maybe to big blocks if they will fit.

By the way I had a 76 233 in 1982. Great boat.

 

This is your best bet.  Quite honestly, a plain old crab (& intake) swap will not yield anything realistically on a stock motor in a boat.  Just won't.

Talk to some mechanics that have been around a while, and they'll even tell you how the 302's and 351's all ran a particular hull the same speeds, although one would tend to think the 351 would be faster.  Just wasn't true.

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72/76formula
"Seaman"




Joined: November 22 2005
Posts: 24
Posted: December 08 2005 at 00:00 | IP Logged Quote 72/76formula

74Formula233 is right, you can not just change the intake and carb on a moter, and expect it to run as good as one that was set up with a 4 barel carb, its not going to work , whats worse is you will destroy the valves as well as carbon up the pistontops big time as well as fileing out plugs left and right. what happens is to much fule is loaded into the cylnders and the valves are not set up for the extra fuel, the plugs will file out and you will have one crapy running moter. best advice rebuild or replace the 2 barrel carb and stick with it.

 

jeff.



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