Top pin pistons??

[tharris003]

This may be a stupid ? but here goes. What is the difference and advantages if any, of a top pinned piston vs. regular?

 

[GFinch]

If you can get them use them. Or like me have them done.
Some might object, butt I don't have options.

OMCease!

Theres a post started by Lou use the search to find it. Below is what I posted then. The true cost was, 1st place including a fully rigged boat.

I feel your pain!
The piston with the bent over locating pin was the last set I didn't have top pinned. Lots of hours. Cost, WON Bass fish off at Shasta Lake.
The piston with the small pin holes was from a set that was top pinned by John and it had the piston circlip come out and dance. 18hrs

I will still have my pistons top pinned.
We all have trophys.
Attached Thumbnails

 

[whipper]

Gary it also depends on your cylinder wall composition weather or not top pin pistons are right for your motor or not correct. I wont go into detail because I'm not very Savoy in this regard.:banghead Some one like Gary and others can explain this better. Baisicaly if you have say a motor like mine a stock 225 pro max they have steel bore cylinder walls and rev to 6750 limmitter. The stock side pins work fine in this application. If you want to rev above say 7000-10000 you need to change a lot of things like the go top pinned and nickel/ceramic walls ect.The steel bore gets to hot above 7000+++ and will weaken the cast side pins{melt** like I said theres more to it than I can accuratly explain but if your thinking about going top pinned dont worry about it unless you have a high rev motor like a 260/280 ect.

 

[Myron]

I have seen side pins come out of bone stock 200's before, it is not from heat or rpm's per say, it is the design. I had a stock 225 pro-max that lost a pin, it actually fell out when I pulled it apart, also all of the others were loose.

 

[whipper]

I have seen side pins come out of bone stock 200's before, it is not from heat or rpm's per say, it is the design. I had a stock 225 pro-max that lost a pin, it actually fell out when I pulled it apart, also all of the others were loose.

Ya thats another thing for sure ive hear of that happening also Myron. Its by design.

Can you go top pinned with steel bore? I was under the impresson most top pinned should go with nick cores?

 

[tharris003]

Not going to be rebuilding now, Block is completely destroyed we got out large chunks of the inside of the block and peices of the ring from right behind the prop that fell through the exhaust not to mention all of the metal we found in the pan. Going to go with a new powerhead now from Mercury with one year warranty for $4,600 plus shipping.

The guy who sold me the boat tinkered with the motor, he disconnected the temp sensor there were quarters with small holes drilled in them in place of the thermostats and a couple of other reasons is why it ran hot, it had top pinned pistons and I originally was wondering if I should go back with them or not.. Thanks for all of the information that ya'll shared....

Thanks Again,

Tommy

 

[whipper]

Thats great to go with a new power head but sucks you have to spend the hard earned cash! At least youll know what youve got and and taken care of get many years of trouble free boating, hopfully. All those horns and buzzers are there for a reason dont know why anyone wouldnt want a warning buzzer not to go off? Theres nothing wrong with side pinned pistons on a stock motor at all. Theres more 225,s with side pinned pistons running great than there is topped pinned 225,s. I had this same question before and after talking with several top engine builders they all said the same thing. Theres really no advantage as long as I entend to run the motor recreationaly and kept the stock rev limiter. Most said the side pins will do well under 7000rpm. Its another story if I planned on running over 7 often though.

 

[fishnfireman]

3 out of 3 -----Ain't bad...

I have had 2-----225 promax motors and 1 280 that ALL lost a side pinned ring.

The first 225 did it twice.....Both of the 225's did this with a stock rev limiter.

 

[Myron]

you can run top pinned pistons in any kind of bore, and I highly reccomend it

 

[whipper]

3 out of 3 -----Ain't bad...

I have had 2-----225 promax motors and 1 280 that ALL lost a side pinned ring.

The first 225 did it twice.....Both of the 225's did this with a stock rev limiter.

Really thats not the impresstion I got from most 225promax owners Ive read about. Now ya got me second guessing what Ive been told buy others?.?? Myron oops now that I read my post I ment to say that if running over 7000+ its not only the top pined pistons youll need but a nic bore or something that reduces friction better than the stock steel sleave will. Im a little rusty havent been around for a few months.

i was under the impresstion that the stock pistons were pretty reliable though with a mostly stock setup. Would the unreliability of side pinned on a stock motor be more builder related after a rebuild than a factory build? You mostly always get brand new motors dont you FFM/ did the failures happen after a rebuild or from the manufaturers original build? This would be a good new thread.

 

[catfish123]

My opinion, not based on fact, is that the great majority of 225 Promax motors are OK with side pinned pistons. Most people who have no problems with their motors don't post about it on message boards. You will always hear about the failures. Certainly they do happen, and hopefully my motor won't become one of them.

 

[Myron]

if you are in question of a failure, pull your heads and look at the bores, if the pins are loose you will see where it is rubbing the cylinder, I have been lucky to catch a couple, but now I just top pin every motor.

 

[chad202]

I think it just depends how lucky you are and how your motor is setup and what temps it runs. I lost one in my promax. It happened after holding it wide open for a few miles turning 7200rpm. That was the longest I ever held cause I just to run my motors hard. I know guys with 280s side pins thats wot everywhere they go and their motors are now 6yrs old and pins are fine. You just never know. I've also had two top pins come out so go figure.

 

[fishnfireman]

James,

All were untouched the first time they went...But yes the original was before and after.

The first time it went down--- we just,,,wrote it off as bad luck !! We only fixed the one hole and put it back together. The second time that mtr went it was a different piston but the results were much worse. That was a 1997 model 225 Super mag.
The 1999 280 that I bought was bought at a huge discount as a blown mtr. On teardown we discovered it had lost a ring pin but it had not done much damage...After some research and talking to some mtr gurus..It was apparent there was a problem with mtrs from around those year models...We pulled all the pistons and sent them to Marles to be top pinned.
I sold the 280 with my 2003---- 3 years ago. The motor still runs strong today.

When I bought this new 21' I put the 2000 model 225 Pmax which I had replaced with the 280.
Upon mounting it we discussed that it will more than likley--crap a side pin..So I decided to make it my winter project, to teardown and have the pistons top pinned,just for good measure.....(Never made it to winter) It lost number 4 due to a ring pin,.
We rebuilt it and had the top pins put in. It's the mtr that lost a rod cap about 2 months ago when I decided to remove the oil injection and raise the rev-limit !!!!!! It ran for 2 years after being top pinned..Maybe not a wise choice to take an 8 yr old motor that had never ran over 6800 rpm and start turning it up to 7500.

Even Merc realized there was a problem, as they started top pinning the pistons a few years back. The 280's might have been worse,,,but the 225 can and will do it.
I have a theory as to why I have had such bad luck.
It's my understanding that the failure is caused from the ring pin and the piston being made from different metals and of different size....they expand and contract at different rates..Thus they slowly work there way out.
I feel that since I use my boat about 50 days a year in the winter time. The COLD water just makes this problem worse.

 

[CommonArcWelder]

you can run top pinned pistons in any kind of bore, and I highly reccomend it

DITTO fo' sho'......Better to be safe, than sorry! :smile

 

[whipper]

hmmmm? theres always something to think about isn't there. Now if Merc could only make there motors as reliable as a Ford we,ed be laughing! Oh what did I start buy saying that now!!unch

 

[ImbadBob]

I have had 7 mercs blow up. 2.4 200 , 2.4 xri , 2.4 bridgeport. " most blown up peice of crap ever manufactured" and 2.5 260. All but one were side pins destruction. One 260 was a new quicksilver part with less than 20 hours, rod bearing failure. Put what you want in your motor. I'm done with side pins, If you have factory top pin pistons leave them alone. Also any part IS going to wear out. If you catch it before it cost you alot of money is the best way. If run it it's gonna break. 2 cent worth.
Bob

 

[RBT]

Something to consider before you spend (waste) your money on top pininng side pin pistons, measure the ring lands and the piston skirts. I have never seen a piston with loose pins that wasn't worn out.
While you can, and lots of people do run these pistons, they will never seal well and they are very hard on bores. Not as bad with steel, but brutal on the aluminum liner (nic) motors.

Vertex makes GREAT pistons for ProMax motors, I am a bigger fan of the OEM pistons for the nic motors, but the Wizard/JSRE piston are more than suitable too.

Food for thought.

RT

 

[Myron]

I actually witnessed a 200 EFI that was just put together and started on the hose, it ran for about five minutes, a pin came out, brand new seizeco pistons. One of my Pro-Maxes that failed had about 100 hours on it. I really think it is just quality controll on the parts not being meet

 

[RBT]

Quality control, I agree. The Vertex pistons seem to have that covered.