Mercruiser 470 repower 1978

[surchin]

Hey guys
From california here,

After chasing years of intermittent overheat problems it seems I have a bad head gasket as I'm still losing coolant after running about 5 min now.

So I plan to repower as the boat trailer and transom and outdrive are all good. I've searched old forums but have not found a good thread of someone replacing a 470 with a new motor.

Any advice is appreciated there must be a bunch of these thst have been done. What works and what doesn't?
Thanks much.
Scott

[cfelton]

Hey Scott, have you considered a rebuild or at least repairing what you have. I have a 170, basically the same motor and they are very easy to rebuild and repair. Rebuilt mine in 06 and its still kickin hard.

[surchin]

That's what I have been doing over the years. Is keeping it going piece by piece but this overheat has been ongoing and at this point it's got a lot of exterior corrosion and just not worth the cutting it would take to get all the bolts off to see what's inside. I'm not like you east coast guys with barns. Neighbothood rules about tearing a boat apart in your driveway for my house. They'd turn me in!

So I'm at a point of repair with new or shop for used replacemt cuddy to get me out on the water.

Got new outdrive SEI. Brand. New trim pump. Hull is ok. Usual wet foam below Good transom good trailer. So Ya that's where I'm at.
Just wondering the overall process if someone been through it.

Thanks c

[THEFERMANATOR]

I would seriously consider a replacement 3.7l if it was mine. There are companies out there rebuilding them. And if everything is updated, they're not bad engines. They make similiar power to a 4.3l v6, weigh a good bit less, not bad on fuel, and I always thought they were a perfect fit for a V20. Otherwise your looking at a 4.3l engine, and most likely having to redo your engine bed as the 4.3l mounts in considerably different than the 3.7l. You could also consider a 3.0l, but then you will most likely need to regear your outdrive, still have to do quite a bit of work for the engine bed, and be borderline underpowered when its all said and done.

[surchin]

Thanks ferm

That does make sense. And I have good motor mounts now and the accessories to go with a new motor from my old motor.

My mechanic is reccomending a V8. He is looking into what it would take to make it work. That's where my question to you all comes from. Anyone done this already and how did it turn out.

Can't seem to find any forum where someone has done this swap

Any links to 470 rebuilt?

[THEFERMANATOR]

I have no affiliation or 1st hand experience with any of these remanufacturers, just some I found in a google search. Or you can normally pick up complete running engines for under $500 off of craigslist. I wouldn't go with a V8 myself, too much weight, a gear change will most likely be needed in your outdrive, completely new engine bed, new mounts, most people agree the added power is a waste as you will rarely ever be able to use it, and the cost. Mercury reccomended the 4.3l V6 to replace the 3.7l 4 cylinder.

http://www.michiganmotorz.com/37l470...ww0aAjgM8P8HAQ
http://m.ebay.com/itm/470-MERCRUISER...-/171828567100
https://www.perfprotech.com/first-ma...product/245003
http://bpi.ebasicpower.com/shop/inde...=406_1733_1734

[surchin]

Thanks ferm
I picked those sites up too, feels like the best way to go. I'll let you know how it works out
Thanks sir
Sb

[step up here]

Some time ago a fellow named Aussie supposedly had the hot lick on the 470 motor! Have not hear from him in years and don't know if he ever completed the project.Hope he didn't get licked!

[surchin]

Oh Ya I remember that guy. That was funny. He was all fired up everyday.

So got off phone with mechanic. 10k to put in a 3.0. So instead. We are going to try to bypass the coolant system making it open raw water system. Anyone tried that on this. It makes sense to me. I've been chasing the pressure coolant system. So to eliminate it seems like it will work. No evidence of water in culindRs at this point so head gasket may be ok. We ran a blue devil sealing kit through it

See how she goes

[surchin]

Getting back out there.