Rebuilding an XR4. Piston Questions

[mogfisher]

Hey there. I have a 2.4L 150 hp XR4 I'm building. It needs one new piston and to be bored the next size on that cylinder. My question is about pistons. Looks like I can get a set of Wiseco pistons for around 800 ish. I assume this includes rings and pins. It will cost me approximately 450 for a set of standard mercury rings and one piston @.015 over. Soooo. For a 250 dollar difference is it worth it to go with the whole new piston set and have all 6 holes bored to .020 over? I'm not looking to build a monster, just a reliable motor for fishing. Butttt. if the pistons help things then yay. One thing I can see as a plus is the wiseco piston has the oversize rings available down the road whereas the .015 over mercury pistons are obsolete. Thanks for any info!

 

[j_martin]

Re: Rebuilding an XR4. Piston Questions

Unless you're porting it and upping the compression trying to squeeze some more power out of it, don't bother. If the parts look good, put them back in, replacing only the bad one.

The XR4 is a vert front 2.4 that is pretty well limited by that configuration. If I were freshening one up, I'd cut the heads a bit and raise the compression to about 145, then burn high octane gas in it. Other than that, yer chasing shadows. If you just ring it, and make sure everything else is within spec, it'll probably give you another 20 years.

my 02
John

 

[mogfisher]

Re: Rebuilding an XR4. Piston Questions

Thanks John. Im happy to hear the cheaper way out is a good way to go. Everything else seems good on the motor except for that one piston. There is some slight scuffing on 2 other cylinders but the shop says theyre within spec. After teardown I'm wondering if I didn't cause this problem with the motor by running it. I bought the motor on a trashed boat (also rebuilding) and I just had to hear it run! Once I tore it down I could see the gear for the oil pump is buggered so Im sure it wasn't getting oil. I guess that's what I get for being impatient. But now I'll have a great motor as I'm freshening everything up. Redoing all electrical etc.

So you think I should cut the heads down? How much is recommended to remove?

I think I might start a little build thread on this as I have a few other questions and I think people would get a kick out of watching me rebuild this motor in my dining room. Hey, it's cold in the garage!

 

[Faztbullet]

Re: Rebuilding an XR4. Piston Questions

It will cost me approximately 450 for a set of standard mercury rings and one piston @.015 over.

Ouch... somebody is sticking it to ya. Rings are $23 a set x 5=$115 and piston is $110 from aftermarket(Promarine). The aftermarket rings also fit OEM pistons so thats not a factor. An you dont want to run Wiseco's unless it is bored properly as that motor need about .002 added to finish bore size to live.

 

[mogfisher]

Re: Rebuilding an XR4. Piston Questions

Thanks for the advice on promarine. Those guys are really nice over there. Looks like I can do this for a lot less than I thought. The prices I quoted were dealer prices for the rings and piston so obviously that's gonna be high. As much as I love supporting the local boat shop it would easily price out to be way more than the motor is worth going that route.

Got a call from the shop today that I need to bore 2 of the cylinders as one was questionable so I said go for it. Cant wait to start bolting this thing back together.

Thanks again for the advice guys.