Force 120hp cylinder liners?

[Lance]

Hi,
I have a 1995 Bayliner Jazz with a 120hp sportjet that will need to be rebuilt. I will do the rebuild myself. I think it will take a 20 thou bore to clean up cylinder 4. Are the liners plain steel? They are not chrome or nikisil or anything fancy like that, are they? It appears to be plain steel, but I would like to verify. This is the first time that I have rebuilt a boat motor. Thanks in advance!

 

[JCF350]

Re: Force 120hp cylinder liners?

Steel cylinder walls. See service manual before boring cylinders.

 

[Frank Acampora]

Re: Force 120hp cylinder liners?

They are actually cast, not nickasil, not chromed or other plating, and if damage is more than .040, new liners are available to insert into the block--takes special machining though.

Are you boring and honing them yourself? The (block bearing mounts) enter the cylinder area so it is like boring and honing a blind hole--as I understand it, it takes a slightly different technique than a through hole.

Stock bore will be either 3.3125 or 3.375. Any cylinders worn, egg shaped, or tapered more than .002 will need to be bored. Bore and finish hone affected cylinders to exactly .020, .030, or .040 over stock--what ever they need. You probably have about .0002 tolerance for finish hone, but if you are good, you will have no trouble holding that. The pistons are machined to have proper clearance with these sizes.

I myself prefer Wiseco pistons. They come complete with rings, wrist pins, and circlips, and are easier to assemble that stock pistons. You will need to buy the con-rod small end bearing kit though.

 

[Lance]

Re: Force 120hp cylinder liners?

Thank you both for responding.
Frank, I am having the block machined at a speed shop that I have used in the past for car motors. They are a pretty reputable machine shop. He has bored two strokes in the past. I had planned on using the Wieseco pistons. I was going to order the whole kit from the max rules site or the parts from Seiler marine. I will do the bearings as well since it is apart, they seem to be slightly discoloured (brownish) and I dont want to do it twice.

It is a 3.375 bore motor, the bottom piston started to come apart, and put a fairly decent score in the bottom of the cylinder. It is suprisingly not too deep, I figure a 10 thou cut for a .020 overbore will clean it up. I was suprised to see that three of the four pistons have broken rings and ringlands. I have had the boat for two summers, it was running fine up to the end, I discovered the problem when I removed the plugs to fog the cylinders and saw a dinged up sparkplug. I noticed the boat seemed a little tired the last few runs, I assumed it more linked to my increasing waistline.

Lance

 

[Frank Acampora]

Re: Force 120hp cylinder liners?

Speed shop will know what he is doing.

I never liked those semi keystone stock rings--They busted on me too, and I think the top land is too thin--leading to the breakage. Never had a problem with the rectangular rings.

I re-use bearings all the time--as long as they are not blued from overheating, spalled, or scored. I personally feel that the slight brown discoloration is work hardening and used bearings are better than new. Remember: the crankpins, rod big ends, and crank center sections are all hardened bearing surfaces and you don't replace them unless obviously damaged. That said, repair manuals all call for replacement of bearings upon rebuilding--who am I to question it?