Siezed Mercruiser 470

[bfjou812]

Hi, I'm new here and have a question concerning a 1982 Mercruiser 470 motor. After not running it for about 1 1/2 years, due to low water levels, I tried to start it and found the motor has siezed. I have a borescope so I was able to see inside the cylinders and saw that there is rust on the cylinder walls that looks like it has siezed the pistons. My question is , has anyone bored out this motor and if so what is a safe overbore to go to? I was thinking that if I have to take it out and rebuild it ,may as well get some more power out of it. I was thinking about .030" over . Any thoughts. Thanks for your help.

 

[Bondo]

Re: Siezed Mercruiser 470

Ayuh,...

An Overbore does Not increase the HP.....
It just makes the cylinders salvageable.......

You'll need to talk to a Machinest,+ see what size overbore Pistons are available for it,+ go to the smallest size that'll allow cleaning up the cylinders.....

If you want More HP,+ what I think is a More Dependable motor,.....
Junk the 470,+ drop in a 4.3l, V6......

Btw,.... Welcome Aboard.....

 

[jerryjerry05]

Re: Siezed Mercruiser 470

Take Marvel Mystery Oil,put it in the cylinders let it set over night. Then hook 24volts to the starter.Turn it over and start it up.Try turning the flywheel after it sets with a screwdrive/prybar.I have started them up and haven't needed to bore them out.Jerry

 

[achris]

Re: Siezed Mercruiser 470

Merc do a 0.030" oversize piston... but as the man said, that won't increase hp any....

Chris.....

 

[bfjou812]

Re: Siezed Mercruiser 470

Is the 4.3 a drop in deal or is there a lot of fabrication involved. The boat is a 1982 Regal 18'.

 

[HT32BSX115]

Re: Siezed Mercruiser 470

You may have to change the transom shield and install side(stringer etc) engine mounts.....and the drive ratio and prop pitch may be wrong.....

BUT......you'll be pulling an engine that was discontinued (and a rather poor design at that) for one of the best and most successful marine engines ever put in a small boat....

 

[achris]

Re: Siezed Mercruiser 470

and the exhaust system is different... Is the 4.3 you're looking at complete, including flywheel housing and engine coupler? If not, then you're up for those too. Sounds like the best situation may be to sell off the old unit, for parts, and find a good second hand 4.3 engine, transom plates and leg.... I sold my old '94 V6 (complete including instruments and controls) a couple of years ago for about 7K....

Chris...........

 

[HT32BSX115]

Re: Siezed Mercruiser 470

He's probably gonna need a "donor" boat to swap pretty much everything........might as well just find a "Donor" boat and just keep it.....

 

[CAPTKEV85]

Re: Siezed Mercruiser 470

I Just Rebuilt My 470 I Bored It .030 Over. On Ebay There Was A Rebuild Kit From Oil Pan To Valve Cover. It Comes With Any Size Pistons You Want. I Choose .030 Over. The Engine Shop Said That Was The Best Without Making The Cylinder Walls Thin.

 

[bfjou812]

Re: Siezed Mercruiser 470

Was that falconglobal?

 

[fishrdan]

Re: Siezed Mercruiser 470

I ordered a master engine rebuild kit for my 3.0 from FalconGlobal, pretty good rebuild kit for the money. Only shoddy thing was It came with a 4 piece oil pan gasket, I ditched it and bought the 1 piece marine oil pan gasket. Other than that it I'm happy with their kit.

But, before yanking the engine and dumping $1k+ into the rebuild I would try to oil the cylinders and break it free as suggested earlier.

 

[watermellonI]

Re: Siezed Mercruiser 470

Hi Bfjou
Just rebuilt my merc 3.0 bored to .30 over and wish I had a v6, I d try to unstick the 470 and run it till the end of the season and look for a donor boat. But don t sink a lot of money into the 470 cause yer jus gonna want more power.

 

[achris]

Re: Siezed Mercruiser 470

Guys,

A 3.0 litre produces 140hp at the crankshaft. A 470 produces 170hp at the crankshaft. V6's come in a variety of flavours, 2bbl, 4bbl, TBI and MPI.

2bbl V6 - about 175hp at the crankshaft.... That's only 5hp more than a 470. And the V6 weights quite a bit more.
4bbl V6 - about 205hp at the crank.
Once they moved to the TBI and MPI, power was measured at the propshaft. Through an Alpha drive means about 20 hp loss.

My MPI V6 is rated as 220hp at the prop... somewhere around 250hp at the crank.

So, to move from a working 470 to a 2bbl V6 is worth all of 5 hp.... and even the 4bbl is only going to pick up about 35hp.... Is it worth the expense and trouble? If it was a 3.0litre, I'd say yes... But for that little gain?

Chris.......

 

[TilliamWe]

Re: Siezed Mercruiser 470

bf, I know of a complete 470 sitting is a garage about 5 miles from you (Auburndale) that you could buy complete for $150. It has damage to the rear cylinder pushrods. It was running when it came out of the boat. The goofy charging system was even working. My dad replaced it with a 5.7 for a guy. My dad never took it apart. If you want to go see it, send me a PM and I'll get you the information.

 

[gbb1]

Re: Siezed Mercruiser 470

is 470 still available?I may be in market-85 searay 260,thx gb-gbb1@windstream.net

 

[gettin'even]

Re: Siezed Mercruiser 470

The Merc 3.7/470 uses a cast Ford 460 piston. Readily available in many different oversizes, and fairly inexpensive.

 

[fyrfightr]

Re: Siezed Mercruiser 470

is 470 still available?I may be in market-85 searay 260,thx gb-gbb1@windstream.net

No, the 470 has not been sold by Merc since the mid eighties.

Also this is a 2 year old thread. It is best to start a new thread.