94 merc 175xri oil pump crank gear

[TAGG]

Hello gents, I joined your boards last fall after I bought a 94 procraft 180 pro with low compression on #6. I pulled the power head & put it on a stand wrapped in plastic a week after i picked it up & I finally had some time to pull it apart today. The seller stated the warning horn was beeping & the warning light was flashing but unfortunately he decided not to shut it off right away. Turns out the oil pump gear shredded so that explains that. My question is, what to do with the plastic gear thats mangled? Im going to premix it so its not needed but i understand it should be there for crank case volume. I dont really want to leave it in there, its pretty bad. Should I buy a new gear even though im not going to use it? Also, this motor is pristine & untouched since new. I could tell when I pulled it off it had never had a wrench on a single bolt under the cowl. 4 of the cylinders measure out at 3.501. One cylinder measures 3.502. All have crosshatching still there from top to bottom. Crank journal for #6 is darker than the others but measures the same as the others. I havent cleaned up 6 yet to see where I stand, but I think it will need to be bored. Im leaning towards all new pistons, rings, rods & mains. I would prefer to only go oversize on 6. Would that be a problem? Thanks in advance for any help. Oh, serial # og129736.

[JOE54]

shouldn't be problem at all, would replace gear and use injection system

[TAGG]

Thanks for the thoughts. Since I posted that, I remembered I still have a 200 crank here somewhere that had a good gear on it, so that should solve that problem. I initially was certain I was going to use the oil injection. Kind of like keeping an old car all original. After reading Jay Smith & several others adamantly against using the injection, Im giving in & premixing. I also cleaned up #6 and it finished at 3.5047. Too big according to experienced engine builders so ordered the rebuild kit today from promarine. Going .015 over across the board. Seems a shame as 5 of the cylinders were at new spec, but I plan on having this boat awhile & decided starting with everything new is probably best.

[EuropeanAM]

Be sure to order a complete MERCURY blockoff kit. It is designed to fill the proper voids and retain the bushing in the far side of the block.

While I don't agree with your decision to switch to premix (strongly prefer proper repair of the oil injection system), should you decide to go that route, I would probably NOT install a used drive gear on the crank. You're gonna spin that thing upwards of 5500 RPM's... put a new one in there even if it's not driving anything.

[buster502]

so the old one lasted 25 years,to each their own but i would leave the oil system all factory,you are not building a race motor but i assume you done some research on the stock oil system its a pretty good set up

[TAGG]

Wow! First time Ive ever seen anybody recommend keeping the oil injection system. I started lurking on scream & fly back in the early 2000's when my new to me 2.4 200 blew up. Rebuilt it & eliminated the injection system and it still runs strong to this day. Even back then everyone said dump the oil injection. Quite honestly, I see so many parts for these nla, I figured you couldn't even buy the gear anymore. I signed up on European am just now & see the gear is listed & only 25 bucks. Big surprise. I will be needing more parts & also will need the injection system validated so will undoubtedly be giving Don some business here soon.

[blackboat]

You can do just the one hole with a Merc oversize piston and it won't affect balance...if the others are good.