bearing question

[reeldutch]

wat is the difference between an upper crank bearing and a center main bearing?<br />are these different names for the same bearing?<br /><br />thanks already reeldutch.<br />Great site here.

 

[rodbolt]

Re: bearing question

hello<br /> post an engine HP and year and maybe we can be more accurate. until then one is at the top of the crank and the other is at the center<br /> good luck and keep posting

 

[Dhadley]

Re: bearing question

Usually totally different. The top bearing is a caged bearing inside its own race where the center bearings are split and have a seperate race around them. <br /><br />Exactly what motor are we talking about?

 

[reeldutch]

Re: bearing question

so a 1990 115 evi crosflow bubbleback<br />has a upperbearing center bearing Splitted and a lowerbearing right?

 

[Dhadley]

Re: bearing question

The upper is an enclosed bearing pressed into the upper bearing housing. The center is a split bearing and race. The lower is a roller bearing pressed onto the crank.<br /><br />Good luck!

 

[reeldutch]

Re: bearing question

If i had a failing bearing lower, main or upper<br />does that mean that the crank is damaged?<br />i think that one of these bearings is bad.<br />i took the powerhead of and i'm waiting for a flywheel holder to come in.<br />i took the heads of and found the bottem cillinders had dammage and the rings are broken.<br />do you think that this might have caused damage to the lower crankbearing?<br />i took the bypass covers of to and could clearly see that the rings were broken.<br />The top cylinders had good compresion and when i opend them they looked fine.<br />may be this all comes from a carberator problem.<br />i am planning to rebuild bud i hope the crank is fine.<br />thats what i suspect.<br />bad carberator caused bottem cillinder damage and that cause lower bearing failure.<br />cant wait to open it up.<br /><br />bud i cauld use some advise.<br />thanks

 

[Dhadley]

Re: bearing question

Scored pistons and / or broken rings dont necessarily mean the lower bearing is bad. Just pull the lower cap off and look at the bearing.

 

[rodbolt]

Re: bearing question

hello<br /> the upper bearing is a caged roller. you can remove it and replace it but make sure you have the new bearing in hand before removal. the top crank bearing is not avalible by itself from OMC or bomby. if you buy it from the dealer you will buy a bearing cap assy. the center main is a split roller with the rollers caged in a nylon cage. the bottom bearing is a ball bearing, this bearing is noted for failing. always replace this one as it not only goes round and round but controls up and down thrust as well. and any moisture collects and causes the bearing to rust. you can buy the center bearing as just the caged rollers or the split shell as well.<br /> tear the motor down and asses the damage. remember the alignment on the rod caps is critical.<br /> when ya get all ready to reassemble let me know and I can give you some tips on chasing the motor together on a work bench. I made a power head stand years ago but I have chased them on a work bench before. the center main is dowl pinned to the block and MUST be properly aligned and held in position during reassembly. the wear tolerance on most of the crank surfaces is less than .001". so polish with crocus cloth and measure carefully<br /> good luck and keep posting

 

[reeldutch]

Re: bearing question

thanks rodbold,<br /><br />I'm defenetly gonna rebuild this motor.<br />Thanks for the offered help i really appreciate that.<br />i have a few qeustions already.<br />1- if i messure the bores and the top left and right cylinders look fine but the bottem ones need to be rebored, do i have to rebore them all to get even compression? over all?<br />2- what size hex socket do i need to get the crankshaft housing from the block?<br />3- wat tool do i need to messure the bores?<br />4- wat tool do i need to messure the crank and cyllinders.<br />thats all for now.<br /><br />Thanks without you guys i proobebly wouldn't rebuild.<br /><br />Reeldutch

 

[reeldutch]

Re: bearing question

never mind on size hex socket got them out with a 5/16.

 

[rodbolt]

Re: bearing question

hello<br /> you dont have to bore all cylinders. its recommended for a complete job verse a patch job.<br /> to measure the cyl bore you will need a minimum of a telescope gauge and a 3-4 inch micrometer. then you will need the skill to use one. I can hold a plus or minus .001 tolerance with it but a dail bore gauge is better. you will need a dail bore gauge to check the rods. the tolerance is less than .0005" or one half a thousanths of an inch. the average human hair is about .003. the maximum piston to wall clearence is about .004. to measure the crank you will need a 1-2" micrometer.<br /> the best way is to send the block and crank to a good machine shop. I reccomend rons marine in portsmouth VA. he can resleeve as well as bore and was a factory authorized resleeveing and boring facility for OMC for almost 30 years.they ship UPS as well.if ya have to cut corners then reuse the upper and center mains if they are not scored. I never reuse the bottom ball bearing. it takes to much load and is failure prone.<br /> try not to get over your head on the rebuild. it takes time and patience do do it right. I have almost 30 years of experience and training on the various systems.<br /> good luck and keep posting

 

[reeldutch]

Re: bearing question

thanks again for your advice rodbold,<br /><br />I'm absolutely not in a hurry to rebuild this motor and i really want to do it myself.<br />I have a 1989 110 evi (almost the same engine)<br />rebuild by a mechanic and it runs super. Then i found this motor and boat(20'mako 115 evi 1990 for 1200 dollars and i bought it.<br />I thought i can use the motor for spare parts on my 110 evi.<br />When i bought the boat and motor the guy told me that it was running bud it might have a failing bearing. because of weard noise.<br />So i didnt care just wanted the boat and spare parts.<br />I started to take the 115 of the mako and hung my 110 on. i used it the whole season no problems.love it.<br />So i took the powerhead of and starting to tear it down. everything looks good exept the 2 burned lower pistons.<br />so the next step is taking of the flywheel and stator and timerbase, and than take the crankcase from the block. <br />my plan is to rebore the block and put at least a new lower bearing on.(can i do this myself?<br />i read that i need a special puller to take the old bearing of

 

[NEECAPRS]

Re: bearing question

Lower Bearing: You don't need a special puller for the lower bearing. I always use a standard NAPA puller. Don't hammer the new bearing on. Dust the crankshaft journal with WD40,heat the bearing to 300F(NO MORE!!) and drop it on. Then reinstall snap ring. Be sure you're ready to have the bearing on permanently. Pulling them off damages them and you'd have to put on another NEW one. For example, don't forget to put the retaining plate on-the right way!!-first.<br />Good luck and don't rush!

 

[rodbolt]

Re: bearing question

hahahaha yep<br /> the old look down and notice the retainer on the workbench about the time I slide the bearing on. <br /> I did that once<br /> I use a press to remove the old one but a puller will work. I have used the retianer and changed the lower bearing without seperating the crank halves. I use a toaster oven and a pair of clean gloves<br /> heat the bearing up and be ready. and make sure you slide it all the way on and hold it there. I have seen them slide back down a bit then stick.<br /> good luck and follow the manual.

 

[reeldutch]

Re: bearing question

thanks again,<br /><br />my neighbours doughter inlaw her father owns a big Marina here on Long Island.<br />my neighbour told me he will rebore the block and repair the heads.<br />now this is for me the first time bud do they tell me what size pistons to order?<br />i guess so?<br />and when i order the pistons shall i stick with omc ore are there any better ones?<br />bud lets not get to far ahead first i have to see the crankcase come off hopefully this week.<br />will keep posting<br /><br />reeldutch

 

[NEECAPRS]

Re: bearing question

Rod and Reel:<br />Rod, yeah, I feel like I invented "clever" moves. My first oil change on a car was a double change(or rinse and change) when I forgot to put the drain plug back in. Nice to know I've got company!!!<br />Reel, Your neighbor will probably want to estimate how far oversize he'll have to bore it then ask you to get the new piston so he knows exactly what size he's shooting for. There are good aftermarket pistons that will run and last as well as the OMCs. Let us know if you need sources.

 

[reeldutch]

Re: bearing question

As far as i can tell this motor has never been rebuild so if the damage isn't to bad i will be best of with 0.020 over.<br />i browesed on different websides and found a kit including pistons,seals,gaskets,lowerbearing,thermostates<br />on powerhead exchange.com<br />bud what is the difference between cast ore forged pistons?<br />wat is better for me?<br />and is this a good way to order the stuff ore are there better places?<br />$ 575 sound cheap to me. wonder if its good?<br /><br />thanks reeldutch.

 

[reeldutch]

Re: bearing question

i am trying to get the old gaskets of the bypass covers and exhaust cover.<br />whats the best way? with scraping i'm afraid i will damage the bypass cover.<br />Is there a chemical that i can use to desolve the gasket sealer?

 

[Dhadley]

Re: bearing question

As for the cast vs forged deal, the forged are stronger and quieter than cast. Also the Wiseco 31 series pistons are electra coated. If .020 will clean it up you can use the 3173P2 pistons.<br /><br />Good luck!

 

[reeldutch]

Re: bearing question

When i send the block out to the machine shop<br />will they clean all the carbon buildup off the exhaust ports? or do i have to do this before i send it out?<br />and i read that cast pistons will last longer or is that a sales pitch?<br />forged pistons sound good to me and are probably most common?<br />still waiting for my flywheel holder to come in.<br /><br />reeldutch