New Mercruiser Owner

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72seastar

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i recently acquired a 1986 mercruiser 170 in a boat from my dad we are rebuilding the cooling system but i was wondering is there anything i should know about these engines?
 
Don S

Don S

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Re: New Mercruiser Owner

Well, it's common name is a 470.
It was a Mercruiser designed aluminum block, open deck design with a Ford 460 head. Any overheat will probably cause a head gasket to fail due to the open deck design.
It had an outboard style rotor stator charging system. Didn't work very well, and some of the parts are NLA (No Longer Available) and the ones that are are big $$$. There are kits to convert to alternators, but some aren't really great kits.
Leaks of antifreeze past the cam seal into the oil is a common problem. Merc recommends a new cam if grooved but speedy sleeves are a work around .......
other than that, they do have a lot of torque for a 4 cylinder, and when they run, they run great.

Since you have one, here is the OEM service manual for it. It's a must with that engine.
http://www.4shared.com/document/zTbCbkDD/Service_Manual_08.html
 
CobiaXL

CobiaXL

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Re: New Mercruiser Owner

I had no idea the 470 was aluminum block engine,Learn something new every hour here.
 
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Bamaman1

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Re: New Mercruiser Owner

72Seastar:

The 470 has very good mid and upper rpm power. As with all 4 cylinder I/O motors, they're a little slow out of the hole. The 4.3 Chevy V6 motor replacement for the 470 is a great performer in every way.

The 470 as previously mentioned used a head from a 460 Ford--also pistons, rods and bearings from a 460 Ford. They were meticulously assembled by Mercury engine machinists--every bearing was different.

Cooling: You just need to clean the heat exchanger periodically, and keep it filled with a 50/50 antifreeze solution. At least the motors didn't freeze up like other car based boat motors.
 
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72seastar

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Re: New Mercruiser Owner

we got a brand new heat exchanger and well pretty much everything related to the cooling system. the alternator/stator bits kinda scaring me now..... whats a good kit to turn it over to the regular alternator run? anyone have a link to said kit? also whats the estimated top speed in a 20 some foot fiberglass ski boat?
 
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stonyloam

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72seastar

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Re: New Mercruiser Owner

well got it back together it already had the alternator kit lucky me.... changed both the bellows pipes.... that was the worst part of the hole ordeal.... well that and the shift cable adjustment. had it out for the 4th of july. put in on the water kicked her into reverse and it worked fine put it in forward to move around the other side of the dock and forward worked fine. went to reverse to slow down and stop.... NOTHING..... had to jump in the water and grab the boat and dock to keep from smashing into the rocks luckily i had forgotten to grab my phone outta the truck so it stayed dry but soaked my wallet and everything else in my pockets got it turned around by hand and fired back up and went out anyway with just forward. we were out on the water from 6 to 10 with no major issues ran her through the paces watching water temp and oil pressure both stayed in the safe range so i pulled my ol' lady and my sister on the tube and had a good outing. went back to the dock before the fireworks were over so we could get outta the water without being pushed out i had my brother up front to grab the dock since i hadn't planned on having reverse but i thought what the h$ll i'll try it and it worked perfectly i shifted in and out a few times and it worked each time..... maybe it just needed to be ran and brought up to temp for awhile.... i dunno
 
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Bamaman1

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Re: New Mercruiser Owner

The heat exchanger is a very simple thing. It's got a bunch of brass tubes running down the middle (with antifreeze in them), and fresh water circulates around the tubes. You just pull the whole assembly and take the end caps off--and flush out all the tubes. Then you flush out all the hoses attached. Reassemble it, and fill the antifreeze like you would do in an automobile radiator.
 
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stonyloam

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Re: New Mercruiser Owner

Bamaman1 said:
The heat exchanger is a very simple thing. It's got a bunch of brass tubes running down the middle (with antifreeze in them), and fresh water circulates around the tubes. You just pull the whole assembly and take the end caps off--and flush out all the tubes. Then you flush out all the hoses attached. Reassemble it, and fill the antifreeze like you would do in an automobile radiator.
Click to expand...

I think that is just backwards, seawater flows trough the tubes and the antifreeze is inside. If you take the caps off it is just water not antifreeze that comes out. You should be able to pull the endcaps and clean the tubes with the exchanger in place. According to the manual, never done it myself.
 
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