Formula 233 Registry

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Hello everyone. I'm looking at 2 mid - late 70's 233 Formulas. one has a 351 bored to 408 ci. And the other has 2 4 cyl. engines. Excluding outboard engines, what do most 233 owners prefer. 1 8 cly. engine, or 2 4 cyl engines ?

Thanks, John Hedlund

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 I have an '82 233 with a single Merc 260. I would love to have twins for docking etc. I had the 260 rebuilt last spring and it has plenty of power and the boat handles really well so I am not looking for ore speed. I have seen some of these boats with twin 260 merc's crammed in that space.

twin 4 cyl would be fun.

Hello Steve thanks for the response. Yes i agree docking and general maneuvering in tight places would be easier with twin motors. One of the Formulas i'm looking at has the twin 4 cyI. I heard that two motors are twice the maintenance and hassle, but on the plus side i guess you could limp back in if one quit working. I'm sure there are advantages and disadvantages to each setup, which is why i posted the question here. I figured the people with experience owning both types would have the best advice. Thanks again.

Best regards, John


I just purchased a Formula 233 with twin 4 cylinder 3.7 liter Mercruisers. This is a project boat but I have weighed the options for a long time. I think I have the right boat for me. I started looking into twin engine boats several years ago. Last year I looked at a Formula 233 for the first time and fell in love. 

I have owned inboard competition water-ski style boats for the last 30 years, most with 351W motors. I do all my own mechanical upgrades and repairs.

Stay away from the modified engine unless you know the engine builder and they have a lot of experience with modifying marine engines. Boring an engine reduces the amount of metal in the cylinder walls. This reduces block strength around the pistons. If the engine is older and not a closed system I would be concerned that the block might be susceptible to cracking.

My guess is that other modifications have been done to that engine as well. 351 to 408 is probably stroked too. What pistons and rods does it have? Has the camshaft been changed? what are the modifications to the valve train? Modifications make it difficult for anyone other that the person who developed and installed the performance upgrades to diagnose, source parts and repair. Most performance modifications reduce reliability.

Now that you have increased the performance has the out-drive been upgraded to handle the additional torque, horsepower and RPMs. Most mustang guys I know with 408 ford small blocks are trying to get around 500 horsepower. No stock Mercruiser out-drive from the '70s is going to handle that.

I can tell you my expectation based on my research is that maintaining two 3.7l Mercruisers will be 3 to 4 times the cost of one stock small block Ford or Chevy based engine. The 3.7l is a special built engine with an aluminium block designed by Mercury Marine. Most other inboard and stern-drive engines are marine versions of high production car and truck motors. Parts are more expensive for the 3.7l. There are a lot of good marine techs who have no experience with this engine so they are afraid of it. There are some quirky issues with this motor.

That being said, I purchased my boat because it is what I believe will suite my upcoming needs the best. I intend to travel a lot by boat so I had to really figure out what was important to me.

Here is a simplified version of my list.

Cuddy cabin and toilet: I want to be able to sleep overnight

Twin Engine: need ability to drive boat in the event of power failure with one engine.

Closed Cooling System, salt water compatible: I want to be able to run the Intracoastal and maybe even venture out into the Gulf when I'm ready.  

Trailer-ability: I didn't want a boat with a beam width that required a permit every time I want to move it.

Economy: I am hoping the 3.7l is relatively efficient. 

Upgrades I intend to do: larger heat exchanger, alternator conversion, Pertronix Ignition, Holley Sniper EFI, Improved seating

Hope that helps. Pictures coming. Mike

Hi John, Given this particular choice I’d go with the single... 351 is a good engine. What did you end up going with? 




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