What do I need to convert

[dkunesch]

I am taking the 260HP Mercruiser out of my ski-boat that has a omc stern drive and putting it in my sedan that has a 302 Ford with a Velvet drive. Both are in the 70's.
What do I need to convert? I see the obvious Bellhousing, Risers, and possibly manifolds, but I am not sure which ones to get and where to find them.
Any hep with this would be greatly appreciated!

Thanks

[mongo75]

Is your Merc a Ford or Chevy block? What gear do you have in your sedan?

[dkunesch]

The Merc is a Chevy Block and the V-drive is a 71C with a 1:1 ratio. The Sedan is a 28" Silverton

[mongo75]

I just got responses to a similar question I had, and they said a 1:1 wouldn't be enough for a boat that size with a small block. Check this out What's the right Velvet drive ratio??

[Jango]

The 260HP motor with a 1:1 gear will not work properly unless the total weight is less than 3500lb which is unlikely. At 6000#and 260 hp, it would require a 13x9 prop which is, not Ideal (high slip)or available. As you slow the shaft down (higher ratio), larger Dia props, with increased pitch are required to utilize the HP.
The 302 Ford w. 1:1, probably was NOT a planing Hull, but semi displacement with a top speed of 22 - 24 mph

[dkunesch]

The 302 Ford was the original motor that came with the boat, you hit the top speed right on the head. The specs for the boat rate its top speed at 24 with a cruising speed of 20.
The skiboat is falling apart but has a brand new motor (The chevy 350). I was just trying to see if I could adapt that motor as it only has about 15 hours on it. The sedan must weigh quite a bit as it sleeps 4, and has a flybridge.

[Jango]

You can put the 1:1 gear on the 350, but it will not be Ideal. Try using the existing prop and keep rpm,s to a reasonable level. You will need a new Bellhousing with flexplate from 302.
I'm assuming the 350 is a stock marine motor. If it has a "wild" cam (low torque) you might not see much improvement in speed.

Existing manifolds should work and posibly Risers

You can get most of what's required from either eBay or Overton's
http://www.overtons.com/productindex.shtml

[dkunesch]

Thanks, I will have to check the manifolds on the merc as the sedan manifolds have the hose on each end for the antifreeze. I don't know if the merc has that. I don't know a lot about the internal cooling systems on the bigger boats.

[Jango]

dkunech, No reason why you can't use the 350 with cooling as it was in the Ski Boat. All that might need changing is the Risers depending on exhaust configuration. In addition, you will need to Add a belt driven "raw water pump"
If your Ford Mercruiser was Stock, the way it came from the Factory, the two hoses are In and Out to "preheat the Engine water", with a third hose going to the riser. Your 350 engine most likely does not have hoses at each end of the manifolds.

[dkunesch]

Ok, after going out and looking at the 2, I see what you are talking about. I doesn't help when I know nothing about this cooling system in the sedan. The sedan has osco manifolds FLCR818. They have a hose coming straight out one end and out the top of the other. It looks like those go to a small dual radiator tank back by the transmission. Then the riser Osco GRR1 has a hose opposite the exhaust hose that looks like it goes to a raw water pump. The ford motor in the sedan has Palmer on the valve covers if that means anything. The chevy motor in the skiboat looks like the manifold only has 1 outlet going to the gooseneck from the water pump and has no raw water pump. And I see where I will need to change the risers for the exhaust configuration. I will need to find a book on the different cooling systems. What is the purpose of pre-heating the engine water, and what does the antifreeze tank do?...Thanks for all your help

Don

[Jango]

Don, It sounds like your "anti Freeze" tank is part of "A closed cooling" system which utilizes Fresh water w. anti freeze to cool the Engine and has a heat exchanger to remove the heat from the Fresh water. This type of system is desireable when the Boat is in constant contact with salt water, since salt is very corrosive. If the Boat is occasionally taken out of the water and cooling system purged of sea water it is less critical, but still desireable. If you choose to use a closed cooling system on the 350, It will most likely require a new larger sytem then used on the 302.
The following should provide some answers:

http://www.boatpartsinfo.com/cooling-systems.html

Pre - Heating cooling water was thought to be helpful, since exposing the Hot engine to Cold outside water was believed to be harmfull. This has since proved to be "overkill" and is no longer done.

[dkunesch]

Thanks, that was a big help. I see I do have a closed cooling system.