pistions???

[geofthro]

Hey there, I just picked up a powerhead off a older 70hp mercury outboard Which was a free be! I now have the powerhead split apart so im about to start ordering the correct parts i need to complete my mission! Now to my observations the cylinders have never being bored out and they remain the standard size and are in good condition, so a quick deglazeing should do it. But my question 2night, Is there any difference in make or brands of different piston manufacturers or should i go with any make for standard pistons?? Or to keep it simple what is a good brand to go with? Thanks.

 

[WillyBWright]

Re: pistions???

Subtle differences in material and machining. I generally advise that you shouldn't mix brands of pistons. It's not a weight issue, but an expansion-rate issue. Aftermarket brands may expand and contract differently than stock pistons.<br /><br />As long as you have it apart, check the grooves on the reed blocks where they wrap around the crankshaft. If they're worn (that's all but guaranteed), replace them. The grooves retain some oil and seal the crankcases. If they're worn enough, they won't seal and the motor will be gutless even with new pistons and great compression.<br /><br />If all you're doing is honing, keep the pistons and replace the rings. If you bore, obviously you'll need new pistons and rings. You don't have to bore all if you bore one. Piston weights stay the same and the additional displacement is quite small when you go oversize, so balance isn't an issue.

 

[Clams Canino]

Re: pistions???

An easy way to see how worn the piston is - is to see how worn the grooves are around the whole piston, particularly near the top. <br /><br />The factory pistons were cast, I don't advise mixing them with the Wisco forged. You *can* mix them with Persan pistons (sold by Pro-Marine and I think Sierra under private label)<br /><br />Now.... I happen to be taking a quick trip back to NH for Christmas in the latter part of the week. As a Christmas present to you, I could take a peek at it and give you an expert opinion on what it needs, so long as your in Southern NH.<br /><br />-W

 

[geofthro]

Re: pistions???

Hey guys thanks for the replys and shareing some of your knowledge! helpfull info like this is always appreciated!!! Two out of three Pistons look fine and the other is a little scorched! Im thinking all new rings and one new piston. Clams canino i appreciate the offer and im sure you could leave behind some good advice with me! But the wife and i are leaving for west mass on thursday to go do the christmas thing! I have friends in Greenville! Who knows we could drop a line in the water one day! Bring on spring!!! Theres fishing to be done!!!. Chears.

 

[Clams Canino]

Re: pistions???

Hmmmmmmm too bad.... if you had *really* good fishing connections, I've been known to trade new pistons for lobsters - since I *do* miss them so. <br /><br />I'll be checking the board from Portsmouth. <br /><br />-W