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  1. #1
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    Different Bore Sizes

    I have just torn this motor apart and every piston on the port side is .030 as stamped in the middle of the piston and every piston on the starboard side is stamped .015. I do not know why this is as I just bought this boat/motor set up and it blew up first time out. The #3 cylinder is messed up as the ring came off and tore the piston and cylinder up and I'm going to have to bore it. I'm going to send my pistons to get them top pinned and send my injectors to Brucato for sure to solve any problems there, but what should I do about the different size's? Should I just get the #3 bored to .030 and put a .030 piston in it and leave #1 and #5 at .o15 or do I need to bore them all out to .030? I want this thing to hold together for sure but I also do not have alot of money to throw at it. Jay Smith was a great help the other day as he knows his stuff for sure and Mr. Marles is alot of help as well but I hate to bug these guys, I'm going to call them but any suggestions would be great. Thanks for any/all help!
    89' 21 foot Norriscraft
    93' 2.5 200 XRi EFI Merc.

    If you aint going fast then your wasting time!

  2. #2
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    You will get many different OPINIONS on this. I build engines like that all the time with different bores. The factory service manuals will tell you to build them that way. But they are others who will tell you to bore them out to make them "EQUAL". Just my .02

    What engine is it? The 93 2.5? If so, I will give you a manual on it if you want. Just PM me.

    Welcome to Scream and Fly!!!!!
    James Perry

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    Wrenchin2 has the right outlook,unless your building a premier class race engine I wouldn'tbe too concerned about the different size bores.I probably wouldn't be worried about top pinning either,for a 65-7000 rpm motor, but the injector cleaning with Tony is a must unless you want the same problem again.Good time to install our reeds while it's apart,Brucato stocks em,Chris

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    Quote Originally Posted by dwboater-fisher View Post
    Jay Smith was a great help the other day as he knows his stuff for sure and Mr. Marles is alot of help as well but I hate to bug these guys, I'm going to call them but any suggestions would be great.
    Jay will probably tell you to run it with odd cylinder. I was talking to him last night and he stated his guy charges him $28 per cylinder and $25 if he does all 6. You will also see him post to bore a damaged cylinder and go on. Most recent is in the "MELTED Piston" thread here. I have done them like that for year for customers with no issues.

    Quote Originally Posted by Chris Carson's Marine View Post
    Wrenchin2 has the right outlook,unless your building a premier class race engine I wouldn'tbe too concerned about the different size bores.I probably wouldn't be worried about top pinning either,for a 65-7000 rpm motor, but the injector cleaning with Tony is a must unless you want the same problem again.Good time to install our reeds while it's apart,Brucato stocks em,Chris
    AND be sure to index your flywheel to test your switchboxes if not replacing them. I have had several this year that the cause of failure was a switchbox "cross firing". That is the reason I replace mercury V-6 switchboxes on EVERY rebuild. Too common for failure and you never know when they will fail. I give a 1 year warranty and I am not going to trust a used switchbox t be good today and kill a engine tomorrow!!! My wallet or wife wouldn't like me! Just my .02 and practices.
    James Perry

  5. #5
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    I NEVER build motors with unlike bore sizes just my policy. The "manual" also say its OK to run nylon con rod bearings too,but who's gonna build a motor with that junk in it when its down for rebuild when a "real" bearing costs a few $$ more...

    And yes I build ALL my engines as if they were WORLD CLASS Race engines from fishing to all out race maybe the reason customers use me,I might add I've never had a customer turn me me down because of my building methods ,price or suggestions, I find most when a motor is down most want it fixed repaired or modified so that the maximum of life will be extracted...

    Others as James do their own "thing" and I hear build a quality engine, do we all have to agree as to how we get there NOPE , pleased customers after the fact IMO is ALL that matters..

    After James and I had a conversation last night about the 2 - 3 motors a week I build he seemed in disbelief. . I wanted to tell him that 2 Sundays ago Jim Brinkley owner of the boat that won the SITC last year showed up here at 8:00 am at 5:00 PM he left after the motor was torn down completely , rear of the chest was opened up more on the mill I did some hand porting, honed , re ringed , changed all seals, ALL bearings changed, both ends of the rods honed , assembled did a complete electrical test, ran motor 1 hour on run stand set all fuel curves for up coming race... Don't believe me I will furnish his number..

    BTW: Most Pro Max engines that I tear down because of blow ups are because of the locator pin failures and none have ever seen over 7500 rpms most never 7000... Don't believe me come by there is ALWAYS a steel sleeve block damaged because of a locator pin failure laying around ..I ALWAYS top pin ALL the motors I build ( NO EXCEPTION ) just ANOTHER thing I do to bullet proof my customers engines along with using TDR reeds as well as have Brucato do my injectors... 3 things I remove from possible failures during a rebuild...

    How a guy achieves HIS customers trust , and complete satisfaction is the real and only issue...Out of 5 guys in the motor business I wouldn't know 2 that totally agreed on every or any aspect of motor building , assembly, and mods...

    My .02 and My practices,

    Have a good one ya'll...
    Jay
    Jay @ JSRE


  6. #6
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    Jay as always thanks! Wrenchin2 I appreciate all of your information as well. I have built some car motors and have run alot of boat motors but have never really torn them down and rebuilt them so I'm up for any and all info here and you all have been great! Chris, I will look into your reeds!
    89' 21 foot Norriscraft
    93' 2.5 200 XRi EFI Merc.

    If you aint going fast then your wasting time!

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    Some years back when Land and Sea Distributing became affiliated with Mercury Marine they became an outlet for the overstock of repaired powerheads mercury had from warranty repairs.I have a lot of experiance with these motors,come behind many of these so called reman motors.Many have an interesting mix of standard and both oversizes,and although it seems to be acceptable,it seems second class to me,especially when you read the flyer "all mercury rebuilt powerheads will recieve the following new partsiston rings,gaskets seals and o rings,bleede lines,poppet valves,rod bolts,rod bearings,attaching hardware[gasket],and...phantom black paint,all other parts as required.When they say "start original,stay original",they seem to mean it.
    We re-manufacture powerheads here,all cyls bored or sleeved to fresh new specs,new pistons, rings,bearings seals,poppet valves,oil gear,thermostats and small parts,...and black paint.
    This thread began by a fillow asking if he could run a 030 piston between two 015"s on one bank,030's on the other bank,not if it would be acceptable as a premier world class race motor.It's nice to have standards,high standards,but not all motors and customers require the very finest of offerings to be added to a service project.And we do use new head gaskets,every time,chris

  8. #8
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    Quote Originally Posted by Jay Smith View Post
    I NEVER build motors with unlike bore sizes just my policy. The "manual" also say its OK to run nylon con rod bearings too,but who's gonna build a motor with that junk in it when its down for rebuild when a "real" bearing costs a few $$ more...

    Jay
    Sorry long....

    You know I love ya man. I do respect you so don't get me wrong....

    I actually love the platic rod bearings because I can change out the needles. I look at them like what is the difference between the rod bearings and the center mains which are platic caged?? Just my thoughts....

    As far as the disbelief.... I just have to bow down to ya. I know a lot of your stuff gets sent out for machine work. I guess that is what takes me so long is I do all of my machine work. Guess I am slow. You stated last night you send stuff off and work on other areas of the the engine while you are waiting on parts. I reuse a lot of pistons so I bead blast all my pistons that are getting reused which take up time. I reuse bearing and have to clean them as well, more time. Mine are mostly carbureted and I soak them in cleaner, more time. I replace the switchboxes, more time. The only bearing I replace on every rebuild is the lower main bearing. It is just that I read your old post and you state 3 engines a week, 10 balance flywheels a week, and X amount of heads cut a week. X-amount of cut fronts a week, ect. It is hard for me to see all of that work getting done when you work alone and I have a worker that can run the mill and do basicly everything I can do ( I don't let him port only on his engines) and I can't get out the amount of work you do with 2 people. I do other boat work and not only engine work so I do get time taken up in other areas. Yesterday when you called me, I was finishing up a boat I had installed new steering on( I had to modify the dash and a hell of a time getting the new cables in!, which took longer than the charged time), removed the all the modules, removed oil injection, indexed the flywheel and checked the timing, replaced the water pump and a shift shaft seal. Today, I am installing a 76 85HP mercury powerhead after I build the carbs and boring a 82 OMC 200hp X-flow to install a sleeve in.

    As far as the 8am to 5PM rebuild...You are good!

    I can honestly say I have never had a 2.5 to come in with a locator pin out without severe detonation and part of the piston gone releasing the pin. I have had every other type of failure! I have several modified 2.5's that are turning 7K and no failures so far and some have been going for years. I DO replace all pistons on a 2.5L ( the only engine I do practice that on ) but I run side pin Pro marine cast pistons and run them fat. I feel with fat there is no excessive combustion temps to cause the piston to expand and spit out the pins from the differt expansion rates of the 2 unlike materials. Has worked good so far and haven't had any issues.

    AGAIN comes down to personal preferences and practices. I have had good sucess for years with my practices and unless something drastic can change my mind, I will contine to do so. I know we have bumped heads on several areas such as leakage test precedures, idle relief engines, and 2.5 cylinder specs. If everyone had the same opinions, it wouln't be any fun. BTW, they guy in Maine is loving his modified idle relief engine.

    I respect you and your opinions/ practices even if I don't practice them and I know you respect me and some of my opinions or you would not have call me in the past and asked my opinion on some of the fishing engines stuff as they are not exactly your cup of tea. We are in 2 totally different worlds, I don't build race engines, I build modified fishing engines from 70 hp- up. I have for years and I still sometimes find myself needing to ask questions when I run into something new I haven't done. You would be the first on I would call if I got into issues on a 260Hp as the only thing I know about them is they are EXPENSIVE . That is the good thing about S&F is there is a vast amount of knowledge. Someone has done it at one time or another. We just have to be careful of the one who can only read and post though!!!!!You know what I am talking about.

    You coming to Jasper this year?? If so, I will buy ya a cold one!

    again, no disrespect!!!!!
    James Perry

  9. #9
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    Wrenchin2 I sent you a PM, you guys are great! I love the different ideas and oppinions being thrown around on here. If it weren't for these different ideas and oppinions everyone would be out there running stock engines with the same if any modifications, its these different oppinions that makes building an engine what it is. For some of us we just dont have the money to play around with different ideas like we wished we did! Keep it coming guys, any ideas as to what to do to get a little more power for not much more while I got her apart or mods that should be made for longevity? I open for ideas here, cheap ones hopefully, and a good shop to take this thing to for the machine work that will do a good job!
    89' 21 foot Norriscraft
    93' 2.5 200 XRi EFI Merc.

    If you aint going fast then your wasting time!

  10. #10
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    Sent you the manual and what I knew about machine shops in Nashville. There is stuff you can do but, if you get too deep you will have to replace the ECU to keep up with the additional fuel requirements or switch to carbs and be basicly unlimited in what you can do. If it is on the 21' Norriscraft, and like the 20' Norriscrafts, the 20' boats were strange in that they were easy to get to 70mph and took a ton more power to get much more out of them. I will send you a link to one I recently don on a 20' Norriscraft.....
    James Perry

  11. #11
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    This thing was pretty quick last week when I had it out I know that! I am hoping it the
    ecu will put enough fuel in there to not run the cylinders dry therefore causing the same problem I have. There has been some concern as well that running it with this ECU over 6000 would cause this problem, what is your .02? I'm also thinking of milling the heads since once got beat up a little but it will seal, i'm thinking maybe just put thin head gaskets on it will do the same?
    89' 21 foot Norriscraft
    93' 2.5 200 XRi EFI Merc.

    If you aint going fast then your wasting time!

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    See what Tony tells ya on the injectors if #3 was not flowing correctly. It may also have been a switchbox as they can take out 1 cylinder. After it is together I can walk you through testing them. I have seen more of that this year than I can shake a stick at. If it was a ECU, then it would effect 2 cylinders as it fires the injectors in pairs. As far as over 6k, they are fine. I would opt to machine the heads to remove the damage as the damage can cause hot spot on the thin pieces of aluminum and cause detonation. This is like haveing a bunch of spark plugs in the cylinder. Shaving the heads is safer plus the squish band (distance between piston and head) remains the same for a safer engine. The fuel curve on most ECU's are fat enought to increase compression with no issues. If you want more safer power, find a 7 petal front, intake and 225 ECU then port your engine to 225 specs (200 is very close) and be that much ahead of the game. Your injectors are the same as a 225 and if you tell Tony your plans, he can insure they will flow good enough for the project. Just my opinion though. Some don't like mismatching fronts. I have done it many times in the past with good sucess. Good luck on your project!!!
    Last edited by wrechin2; 09-10-2010 at 01:58 PM.
    James Perry

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    Thanks James ,
    I TOTALLY respect you and feel your a 1st class guy and know your stuff within your expertiece that the reason I value your information and use you as a source of CORRECT information when fact gathering ( BELIEVE you me your opinion is one of very few I will act upon with ZERO questions , if you tell me an answer about a fishing motor electric or EFI issue I consider its gospel ! )

    Thanks again,

    PS James : Thats ALL I work on IS power heads. No boats, gear cases., OR motors on down housings, they MUST be sent as only a power head assembly .....

    Maybe thats the reason I can turn them around as fast as I do.. My mill is set up on KILL for cutting heads , front halves and blocks... I have at least 30 air tools with rotary files of all designs , lenghts and cartridge rolls hanging on racks and a 4 air hose manifold with ALL the tools loaded ready to do the job at hand ( no time wasted in changing files OR even air tools to air hoses they are hooked up and ready to be used... )

    No I will not attend Jasper , but I plan to attend the SITC race in HOT SPRINGS, ARK the 23rd.....

    Peace,
    Jay
    Jay @ JSRE


  14. #14
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    Quote Originally Posted by dwboater-fisher View Post
    I have just torn this motor apart and every piston on the port side is .030 as stamped in the middle of the piston and every piston on the starboard side is stamped .015. I do not know why this is as I just bought this boat/motor set up and it blew up first time out. The #3 cylinder is messed up as the ring came off and tore the piston and cylinder up and I'm going to have to bore it. I'm going to send my pistons to get them top pinned and send my injectors to Brucato for sure to solve any problems there, but what should I do about the different size's? Should I just get the #3 bored to .030 and put a .030 piston in it and leave #1 and #5 at .o15 or do I need to bore them all out to .030? I want this thing to hold together for sure but I also do not have alot of money to throw at it. Jay Smith was a great help the other day as he knows his stuff for sure and Mr. Marles is alot of help as well but I hate to bug these guys, I'm going to call them but any suggestions would be great. Thanks for any/all help!
    You're basically working on a "Last Chance" block unless you resleeve it. Merc say's 3 odd slugs are o.k. 4 is not. They claim the weight difference isn't enough to affect the way the engine runs and I tend to believe that. So the question is, do you spend the time and the money to do three more holes or do you find a clean block and start over. Your saving grace is that they are all on one side so you only pay one setup fee. The bad part is that the next time you loose a hole you're going to need to go to Wiseco's or re-sleeve.

    Jay's perspective on engine building, fishng or race is the same as mine. There's not doubt in my mind that it's the better way to do a rebuild but is it going to make a huge difference?. I don't know, I've never done it any other way so I can't compare.

    If it were my motor I'd pull it all apart and look at all the holes for bore and taper before I put another nickle in that block. If any of the .030 's were questionable, I'd go looking for a good used block and spend the off season doing it right.

    It really suprises that it takes Jay 8 hours to do a motor. I thought he was faster than that.
    Steve Schefer

  15. #15
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    Steve,food for thought.Did a little math,easy formula,stock 2.5 merc is 152.97 cubes,25.5 cubes per cyl.Boring 015 brings it up to 153.1, or .0261 cubes per cyl (1/12%) increase,correspondingly an 030 bore picks up .26 cubes,or .043 (1/6%) per cyl.Dosent seem hardly enough to worry about,in compression,balance or power.BTW,we don't use em in our re-mans because we don't sell motors bored to the max,but you can get nice cast Mallory pistons for a 2.5 in 040 over,chris

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