Mercruiser 470 repower 1978

S

surchin

Member
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
 
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.
 
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 :bat::bat: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
 
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.
 
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?
 
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/37l47...0NTEeTCBBc3zsemjsgtmns5W7SjFG3Uww0aAjgM8P8HAQ
http://m.ebay.com/itm/470-MERCRUISER-engine-3-7L-170-HP-CORE-REQUIRED-BEFORE-PURCHASE-/171828567100
https://www.perfprotech.com/first-m...ng-block-marine-engine-me224la/product/245003
http://bpi.ebasicpower.com/shop/index.php?main_page=index&cPath=406_1733_1734
 
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
 
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!
 
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
 
Santa Barbara harbor launch ramp. Always thankful to make it back to the dock with this old boat! My patient wife and loyal golden retriever
 

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I have a stainless and aluminum sheet T Top. Works pretty good. Bracing could be better.
 

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Craigslist and other sources I would look into a running 470 that would be the best way to go.It's not the fresh water system killing it. More riser bad operating when lower in coolant (steel head aluminum block) just a few reasons. Actually it boils down to general maintenance.
So that leaves it hard to fine a good one. Most of the time the good ones are usually in a boat that sat for years and rotten out. Maybe consider closing the transom hole go bracket and outboard. Ten thousand for a new 3.0 litre is out. I have two of these boat with the same motor that still run fine for now. Good luck with your decision.
 
Mercruiser didn't put a heat exchanger on that engine for no reason. The mixture of aluminum and dissimiliar metals is BEGGING for corrosion. If you're doing it for a short time and plan on throwing the engine aesy afterwards, go ahead. Otherwise install the 4" heat exchanger and fix your combustion leak.
 
Have you checked your bilge for coolant? I had an overheating problem with my 170 when my outdrive impeller was bad and the coolant pressure caused the back seal in my water pump to fail. The coolant leaked out a relief hole and into the bilge whenever the engine got up to temperature.

If I remember correctly, the front end of the cam shaft drives the water pump and it was scored a little so I got a sleeve for it, installed it, screwed up a seal putting the pump cover back on and with some advice from Spare Parts was able to get it done on the second try and no more leaking.

It's a bit of a job - you have to remove the harmonic balancer, which is part of the alternator. I found all of the magnets were loose, lots of rust on the iron balancer and some corrosion on the coils. I cleaned that up and got several more years out of the alternator.
 
step up here said:
Craigslist and other sources I would look into a running 470 that would be the best way to go.It's not the fresh water system killing it. More riser bad operating when lower in coolant (steel head aluminum block) just a few reasons. Actually it boils down to general maintenance.
So that leaves it hard to fine a good one. Most of the time the good ones are usually in a boat that sat for years and rotten out. Maybe consider closing the transom hole go bracket and outboard. Ten thousand for a new 3.0 litre is out. I have two of these boat with the same motor that still run fine for now. Good luck with your decision.
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I think another 470 is a good option but having to pay a mechanic to do it really makes it a gamble that I'm not sure I want to do. But I'm going to be looking for one now. I see them offered in boats here from time to time. Not real common. If I had time and skills to swap an old motor Id do it but I dont.
 
scook said:
Have you checked your bilge for coolant? I had an overheating problem with my 170 when my outdrive impeller was bad and the coolant pressure caused the back seal in my water pump to fail. The coolant leaked out a relief hole and into the bilge whenever the engine got up to temperature.

If I remember correctly, the front end of the cam shaft drives the water pump and it was scored a little so I got a sleeve for it, installed it, screwed up a seal putting the pump cover back on and with some advice from Spare Parts was able to get it done on the second try and no more leaking.

It's a bit of a job - you have to remove the harmonic balancer, which is part of the alternator. I found all of the magnets were loose, lots of rust on the iron balancer and some corrosion on the coils. I cleaned that up and got several more years out of the alternator.
Click to expand...

Oh Ya I've had lots of coolant in the bildge! I have replaced that gasket you mention here and water pump and impeller is good too. I think I have the h b removed for a standard alternator set up. I'm actually not sure what I harmonic balancer does.
 
THEFERMANATOR said:
Mercruiser didn't put a heat exchanger on that engine for no reason. The mixture of aluminum and dissimiliar metals is BEGGING for corrosion. If you're doing it for a short time and plan on throwing the engine aesy afterwards, go ahead. Otherwise install the 4" heat exchanger and fix your combustion leak.
Click to expand...

Yes I understand. I did put in a 4" heat exchanger few years ago. This is pretty much a last chance for this motor as the pressure in the coolant system is going somewhere and the head gasket leaking seems to be the likely place.

I can't get the riser elbow off now from corrosion and rust. But Im likely loosing coolant from cracks in there too.

I've had the boat almost 10 years and I've done a good job keeping it going. Out boating season is 12 months and Ive managed to get out year round for 10 years with this old motor.

I definately got a motor that had not been very well maintained before me but I liked the hull setup at the time and boat was cheap. I can only say I wish I would have re powered in the beginning instead of eBay parts and labor to keep it going. But I did not have the big money for that. Just had to keep chasing problems but usually got them solved.


Right now I have a lot $ in a new outdrive and trim pump ($!!!) and I'm just trying this new open raw water system as pretty much last resort. The closed cooling system is not working for my motor. We have a good wash down here at our ramp I always flush it straight out of the water so I'll keep doing that against salt water corrosion.

I really have a good feeling it will work. Motor runs great. Starts idles shifts all good. Carbs clean. New electronic ignition My Trailer is good. It's just this dam overheat keeps happening. This is a few hundred dollar fix at this point.

Thanks you all for the input I really appreciate it. Being able to run it by guys that know the situation. I'll post up how it turns out.
Scott
 
Spare or Ferment can probably explain the harmonic balancer function - to me it just looks like a big fat crank pully and it's driving the alternator I put on after the built in one quit working.

Just to be clear, it wasn't a gasket problem. It was the back shaft seal (there are two in the built in water pump - one in the back and one that goes in the front cover before you put it back on - very easy to ruin that seal putting the cover on). If you're getting coolant in the bilge and can't see where it's coming from, I bet that's it. There's a small hole to let coolant drain out (kind of hidden around the back/bottom of the water pump). If you have a good engine, other than the overheating, it's probably worth seeing if you can fix (or get fixed) the water pump, if that's what it is.
 
scook said:
Spare or Ferment can probably explain the harmonic balancer function - to me it just looks like a big fat crank pully and it's driving the alternator I put on after the built in one quit working.

Just to be clear, it wasn't a gasket problem. It was the back shaft seal (there are two in the built in water pump - one in the back and one that goes in the front cover before you put it back on - very easy to ruin that seal putting the cover on). If you're getting coolant in the bilge and can't see where it's coming from, I bet that's it. There's a small hole to let coolant drain out (kind of hidden around the back/bottom of the water pump). If you have a good engine, other than the overheating, it's probably worth seeing if you can fix (or get fixed) the water pump, if that's what it is.
Click to expand...


Thanks s
Yes I did those seals a few years ago. Nope not where it was leaking.
 
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