Mercruiser 470 swap to Mercruiser V8 302

Im trying to swap a Mercruiser 470 4cyl motor, for a Mercruiser 302 v8. The question/problem i have is that the mounting screws for the motor,in the boat, dont match with the new motor. I am very unfamiliar with boats, but familiar with motors. I was just wondering if anyone could help with a solution. The boat is a old TCraft and im not sure of the size roughly 20ft with a v-nest cabin. Any help would be apreciated. Just let me know if you need anymore information. And the motor is blown thats the whole reason for swap. Also the reason for the v8 is that i cant afford a motor really and this is a deal at 200 running.
The well, or whatever its called were the motor is sitting roughly 4 inches below floor level, has 2 front mounting screws about 1ft apart and the motors mouting screws are about 2 ft apart.

Re: Mercruiser 470 swap to Mercruiser V8 302

You will need everything from the inner transom plate foreward to complete a successful swap, as well as possible stringer modification to accept the V8 front motor mounts.....
Your drive ratio will be wrong as well....
The 302 needs a 1.5 : 1 ratio, you most likely have a 1.84 1 no amount of propping will make it right.....
This is quite an undertaking, make sure the boat is worth it.....
When it is all said & done, it would be cheaper to find another 470.....
Welcome to iboats, btw.....

Re: Mercruiser 470 swap to Mercruiser V8 302

Well i also wanted to shy away from the 470 because i have heard such bad things and while working on getting this motor to run before it seized it was just a pain. Basically i dont have the money to spend more than 500 on a motor and i dont want to just give up on the boat. The motor would also come with the gimbile ,housing,exaust,cables,and gauges, and i can opt to get a outdrive for the motor just with out the lower unit for another 150. So basically i think its a deal, but i could be wrong thats why im here first before spending some money thanks for the help

Re: Mercruiser 470 swap to Mercruiser V8 302

I would still look at the mounting situation for the front mounts.....
If there is alot of modification needed, you are looking at a lot of work....

Re: Mercruiser 470 swap to Mercruiser V8 302

So basically your saying that the amount of work needed to make the new mounts would out weigh the price of the motor. I have no problem putting in the work as me and a few friends are taking this project on together. We have refab the entire interior of the boat and now are just stuck with the motor. Im not not sure what i would need to do for the mounts since the well for the motor is just about 2ft by 5ft and the v8 motor is 2ft by 4ft. I just have never fabricated with fiberglass. So i dont know what tools or what all will be needed to complete the mounting fabrication

Re: Mercruiser 470 swap to Mercruiser V8 302

I have no problem putting in the work as me and a few friends are taking this project on together. We have refab the entire interior of the boat and now are just stuck with the motor. Im not not sure what i would need to do for the mounts since the well for the motor is just about 2ft by 5ft and the v8 motor is 2ft by 4ft. I just have never fabricated with fiberglass. So i dont know what tools or what all will be needed to complete the mounting fabrication

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Ayuh,... You need to go to the Restoration forum for the Fiberglass Knowledge.....
It's All Doable,... With the Imagination, Time,+ some Money....

Re: Mercruiser 470 swap to Mercruiser V8 302

I also have a 'sick' 470 in one of my boats...and I toyed with the idea of replacing it with a 3.0.

I figured that I could have a local metal fabricator come up with a crossmember, that I could locate in the engine bay to match up with the front mounts.

Here is a rough sketch of what I was going to do:

Re: Mercruiser 470 swap to Mercruiser V8 302

Rocky_Road said:

I also have a 'sick' 470 in one of my boats...and I toyed with the idea of replacing it with a 3.0.

I figured that I could have a local metal fabricator come up with a crossmember, that I could locate in the engine bay to match up with the front mounts.

Here is a rough sketch of what I was going to do:

Click to expand...

Rocky Road, your sketch is VERY VERY similiar to exactly what my dad fabricated for a boat that he put a 5.7 in place of a 3.7 (470). Only he made his out of wood. It worked well, and is still working well.

Sgthobo, your post worries me a little. You say you are looking at buying a 302 V-8? As in a Ford 302? In my opinion, you are somewhat jumping from the frying pan into, well, another frying pan. Ford hasn't made a 302 in several years, and they quit supplying engines for the marine industry 20 years ago. There are marine only parts for Ford engines that you can no longer get at any price. And whn you need exhaust manifolds, be prepared to pay about twice as much as what you can get Chevy manifolds for.
Also, the 302 Ford was called an 888, and it used a 1.32 ratio outdrive. Not sure why, but it did. It usually needed much lower pitched props that you would normally use. Like a 15 pitch instead of your buddy's boat that uses a 19 or 21. You might get away with using your 470 outdrive with it's ratio, you just would have to experiment with props.

But really, if you are looking at a Ford motor, I say keep looking. Others disagree (and I love Ford 302s), but it's just another can of worms.

Re: Mercruiser 470 swap to Mercruiser V8 302

Well since many have know said a design like this will work thats what im going to try, but will this affect the motor since it will be sitting higher than the original 470?

Re: Mercruiser 470 swap to Mercruiser V8 302

Sgthobo said:

Well since many have know said a design like this will work thats what im going to try, but will this affect the motor since it will be sitting higher than the original 470?

Click to expand...

Not necessarily true...your 470 is on a 'stringer' now. It is more than likely that anything larger will need support slightly forward of your current stringer.

You'll only know when you take some measurements...but, if a fabricated cross member interfers with your current stringer, then you could be using the stringer already there!

Besides...it would be easy to cut out what you have now....

Re: Mercruiser 470 swap to Mercruiser V8 302

have you look craiglist houston for that 470 mercruiser i think i seen one there

Re: Mercruiser 470 swap to Mercruiser V8 302

In case you get overfed with neg. reply's, i have a complete 3.0 4 cyl. for sale(94). a lot easeir to fit in. i'll let it go for 550 + shipping. Can you try to rebuilt your 470, they are good motors. Have fun.

Re: Mercruiser 470 swap to Mercruiser V8 302

TilliamWe said:

Rocky Road, your sketch is VERY VERY similiar to exactly what my dad fabricated for a boat that he put a 5.7 in place of a 3.7 (470). Only he made his out of wood. It worked well, and is still working well.

Sgthobo, your post worries me a little. You say you are looking at buying a 302 V-8? As in a Ford 302? In my opinion, you are somewhat jumping from the frying pan into, well, another frying pan. Ford hasn't made a 302 in several years, and they quit supplying engines for the marine industry 20 years ago. There are marine only parts for Ford engines that you can no longer get at any price. And whn you need exhaust manifolds, be prepared to pay about twice as much as what you can get Chevy manifolds for.
Also, the 302 Ford was called an 888, and it used a 1.32 ratio outdrive. Not sure why, but it did. It usually needed much lower pitched props that you would normally use. Like a 15 pitch instead of your buddy's boat that uses a 19 or 21. You might get away with using your 470 outdrive with it's ratio, you just would have to experiment with props.

But really, if you are looking at a Ford motor, I say keep looking. Others disagree (and I love Ford 302s), but it's just another can of worms.

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you can still find many parts even from kijiji, Ebay,craigslist and buying sell these will help you find MANY MANY of parts. Plus i know a lot of marinas, In Canada that still work and find parts for the 302. DONT forget not much has to be done to marinize a engine, a lot of shops would be happy to do it for you for a price. OR if you have the know how you can do it yourself. i have a 302 ford mercruiser and parts are everywhere, just take a second to look like this forum

Re: Mercruiser 470 swap to Mercruiser V8 302

I see from your other posts that you have been looking through the older posts. That's great, but replying to them at this point is probably not helpful. This post is from a year and a half ago. But welcome aboard!

Re: Mercruiser 470 swap to Mercruiser V8 302

May 28th, 2009

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Ayuh,... Welcome Aboard Dude,...

This all happened almost 2 Years ago... You're alittle Late...

The archives are for Learnin',... Not posting too...