OPSMAD

Hi everyone,

i need some help regarding The OPS .90 blackhead i have broken two rods in two seprate .90's in the space of 3 weeks and the worst thing is one set of bearings where only two hours old
the rods seem to be breaking only the big ends,is there a stronger rod out there on offer or am i doing something wrong? im only running 20% nitro so that wont hurt it im only running the engine to 20,000rpm they are designed two rev higher i know theses engines are old and have been round for some thirty odd years but they still make them today, PLEASE CAN ANYONE HELP[&o]

bobdog262

hey buddy i dunno if this helps i also have the ops maybe an 80 but a black button red cooling jacket..never had a prob ..but..wen i bought it the guy jus put new sleeve and piston in it and he said to lap the engine by hand with wd 40 or it will blow rods.... mayb will help ya out mine runs great after 10 years nuttin ever done to it i also run 20% nuttin more

f16man

I have had trouble with other engines as well I remember one os 77 df I had poped the bottom off 2 rods like that after short run times, I finally found out that the piston sleeve fit at the top was tighter than the rest of my engines but not to the point of siezeing, I removed the head cleaned out the oil from the cylinder and used some toothpaste to lap in the piston,, I know sounds crazy but it worked really good, then I took it apart again and cleaned all the tooth paste out, polished the crank pin with crokus cloth and reassembled with a good dose of castor for assembly and some extra in the fuel,,,, turns out it was one of the best running 77s in the fleet ha ha.

FastBoater

My Feedback: (3)

Use WD-40, it's the best!

srw1960

The piston is to tight at the top of the bore...The faster the engine spins the further up the bore the piston goes due to rod stretch. its to tight up top and grabs the piston to hard and thats whats knocking the ends off youre rods.. you know these cylinders arent straight up and down right??they taper at the top I think they call it band squish its what produces compression in ringless engines..as I look at the pic I can see an obviouse ring towards the top of each piston it looks to me to be way to tight up top..if you are changing just pistons and not using a matched piston and cylinder you will need to find the dimension for the top of the piston as well as for the top of the cylinder and find out which one is off and then fix it by either honing the top of the cylinder or reducing the diameter of the piston..honing is easier thats what the wd 40 and tooth paste is doing...if you have a small amount to get rid of then tooth paste might do the trick but if its alot get a small brake cylinder hone from the auto parts store and use it just go slowly and recheck dimensions often...hope this helps

f16man

The problem is that the cylinder is crome plated and will not hone easy and if you did you will possibly go thru the plating and ruin the sleeve , If it is that tight you can ad some baking powder to the tooth paste and work the piston in a little faster but don't go overboard!!!!!!!!

OPSMAD

THANKYOU HEAPS EVERYONE I HAVE JUST BROUGHT A NEW PISTON AND LINER I WILL GIVE IT A GO,I NEVER THROUGHT OF THAT,I WAS WAY OFF TRACK,I LOVE THE OPS 90 JUST SO MUCH GRUNT FOR A OLD MOTOR,JUST WANT TO STICK WITH THEM, WILL POST A REPSONE IN A COUPLE WEEKS.

IM ALSO RUNNING A O.S 9.B CARB WITH ADAPTOR SEEMS TO RUN REAL NICE AND GETTING OFF BOTTOM END IS SO EAST COMPARE TO THE FACTORY CARB
DOES ANYONE OUT THERE RUN THIS TYPE OF SETUP OR IS THERE SOMETHING BETTER?

HAPPY NITRO BURNING

REGARDS CLIVE

pcnewman

Where are you getting OPS parts? I can't seem to fond them

Squarefour1

I would really like to talk to ya if your around. I have been away from my boat for a good year now. I want the crb you are talking about for my OPS 90. Where and how much? Did you resolve your Seizure issues I read about? Keith Snow 850-259-6469. Good head temp is 210 to 230 degrees. sounds like lean out on top RPM.

advanced builder

If you try to run high nitro (+25%) and higher you need to add racing castor oil KLOTZ CK TOWER HOBBY

f16man

AMEN advanced ,Plus if you know a machinest you can get him to copy the stock rod out of titanium........

HendricX

The OPS likes 15% > 17% synth and 3% castor .. just as K&B outboards.

And the oil-hole on the rod should face the carb.

Make the oil-hole 2mm/5/64" and 'flare' it it little.

I even made a cut with Dremel-disk on the big-end-bottom , just to be sure the big-end gets enough oil.

Ron Olson

My Feedback: (1)

The sleeves will be tight at the top, they're made that way for a purpose. When the heat gets built up in the combustion chamber the sleeve will expand there letting the piston keep the compression. Hone it too much and once it warms up you lose that. Brad Christy makes titanium con rods for most engines and should have one for yours.
Check the sleeve to see if it has warped, it does happen. I had a Nova Rossi that warped so badly that I couldn't get the piston out.

advanced builder

Looking at where you live OPSMAD.I wonder if your also are having cold water problems , try putting a smaller dia pipe inline to slow water intake or a clothespin of some kind to slow intake. Just my 2 cents.

OPSMAD

Sorry have been away from boating for awhile as we got broken into alot of gear including most of my boats was taken but thank god for insurance,
so im starting again with a bellworthy f1 tunnel designed for .45 in/out board so im going to jam in another OPS .90 yes we are nuts here in new zealand bigger is better ha,ha
im taking it out for the first time this sunday we are in the middle of winter here,so will be slowly running it in.You Mentioned O.S 9B carbs,i buy mine from tower hobbies in the usa.cheap as chips you will have to make an adaptor plate to mount though no bigger very simple.Before we got boken into i tried lapping the piston with wd-40 and i must say it works a real treat,running 30% nitro in a 42 inch Aeromarine sprintcat we where on the rough water pulling 70mph before she flipped on me, Racing on a river i know we mad! [>:]

OPSMAD

Hey there yes you are right its pretty cold down here in new zealand with water temp in the winter doesnt get much warmer than 4-7 degrees so most of us run our cooling though the tune/nitro pipe then into the engine manifold then into the head using the smallest tubing we can get here,it does make a massive difference to running & the life of the engine.

thankyou for your valued imput im still learning everytime i go out

advanced builder

OPSMAD , I just looked your from New Zealand ,not Newfoundland .Man my old eyes are going. Water intake,go into the header first then to the headbutton , exit out the head.