repower question for a 17 ' center console

[TownsendsFJR1300]

They are boreing ALL THREE CYLINDERS correct (to the same amount)?

Not just one cylinder, right?

[rodbolt17]

in the two stroke world it is an acceptable practice to only bore 1 cylinder.
I wont do it but the piston weights are all close.

typically when I rebuild one all the cylinders are bored,honed and ports chamfered.
any ball bearings are arbitrarily replaced and all roller bearings inspected.
wristpins and pin bearings are normally replaced.

but REMEMBER, piston/bearing failure is typically NOT the problem.
its a symptom of a problem.
find the cause of the first failure or you may get a repeat performance.

[hydrasports cc]

The plan right now is to only bore the number one cylinder but that will be finalized after tear down. And as others have stated the mechanic will determine what the cause of the failure was. I may suggest to keep the auto oil system and I'll add a little extra to the fuel tank. Right now I just don't have any facts without the autopsy report .

[hydrasports cc]

Thought I would give a " mid way " update. Received an email from the rebuilder today the engine is completely torn down. First good news is no bolts broken during removal. Second good news the crank and connecting rods in great shape. Oil pump/system found to be working properly and will remain intact/functional. Cylinder 2/3 in good shape cylinder 1 being bored this weekend. Parts ( pistons/rings ) to be ordered next week after getting the block back from the machine shop to make sure correct sizes ordered. And the cause of the number one cylinder was the carburetor, in his words the " carb shut down " leading to the failure. So all three carbs to be rebuilt. He basically stated the motor was an excellent candidate for the rebuild and will be a good runner for a long time. Time will tell I hope to get it back early next month and still get her in the water a few times before the cold sets in.

[99yam40]

I always thought they bored and honed the cylinder to the piston they had in hand to be sure it was in correct tolerance , but I do know for sure

[TownsendsFJR1300]

Glad to hear the good news.

If you could, next time you speak/e-mail, can you pin point down what "carb shut down" means.

I have to assume he's referring to a clogged up carb/main jet, due from varnish or debris getting into the carb? Possibly rubber hose break down getting into the sytem?

Also, not brought up, do you have a pre engine, fuel/water separator on the hull(10 micron usually)? Probably wouldn't be a bad investment

[rodbolt17]

years ago you measuered each piston and that's what you did the final bore/hone size to.

now you bore/hone to the correct size and if the piston to wall clearance is wrong you send the defective piston back.

we wont go into knurling pistons but I have actually done it.

tyipically a one hole piston replacement is called a patchem up job.

[99yam40]

years ago you measuered each piston and that's what you did the final bore/hone size to.

now you bore/hone to the correct size and if the piston to wall clearance is wrong you send the defective piston back.

we wont go into knurling pistons but I have actually done it.

tyipically a one hole piston replacement is called a patchem up job.

Yea, I remember having repaired old 4 stroke motors by knurling the valve guides also but they were not outboard motors/

Apparently the tolerances are a lot tighter on the manufactures now a days

[hydrasports cc]

Glad to hear the good news.

If you could, next time you speak/e-mail, can you pin point down what "carb shut down" means.

I have to assume he's referring to a clogged up carb/main jet, due from varnish or debris getting into the carb? Possibly rubber hose break down getting into the sytem?

Also, not brought up, do you have a pre engine, fuel/water separator on the hull(10 micron usually)? Probably wouldn't be a bad investment

Yes I'm pretty sure it was a clogged condition. And yes there is a spin on cannister fuel filter back by the transom.

[hydrasports cc]

OK the motor is back at the shop the top cylinder was bored .020 which is first oversize ? The head is getting a minor resurface to insure a totally flat mating surface. All parts have been ordered the tech believes the engine reassembly will start later this week/early next week. Almost there !

[bajakeith]

holy moly

at the young age of 54 and have been doing motors my whole life !! I would never bore 1 cl..and a lot of times muratic acid and a light hone will bring back a damaged bore..But if that dosnt work then bore all and use the least next size up....I cant tell you how many guys try and tell me about the crap they have read on the net about motors blowing up because of oil injection systems fail....BS>>BS>>BS!!! oil injection systems are THE ONLY way to go !!! it started with the omc VRO they used for over 20 years..but ****head bob who thought he was a boat mech and had NO clue on such system/s told billy bob to premix his gas/oil...50 to 1 is OK at lwr rpm's that's too much at idle and at WOT let the oil pour !! dosnt anyone understand that oil in the gas also makes/builds up carbon behind the rings and on the piston lands and you lose heat transfer..then ya start melting pistons W/poor cooling mixing your oil to gas has soo many downfalls that I could/should write a book about it...do NOT disable your oil injection system..EVER !! and btw its easy to ck pump outlet flow rate....Do you want the mechanic that works on the 727 your flying in tomorrow watching you tube vids on jet repair ?????? GET A GRIP !!

[hydrasports cc]

Received an email from the shop last night waiting on a few internal parts that are on order then will start the reassembly. Currently he's torn down the carb's and is cleaning/rebuilding. Head cleaned up with minor surface grind to insure flatness. And to be clear we are NOT disabling the oil injection system. There was talk up front of doing that IF it was determined to be the cause of the failure. But it was not the oiling system so it is being retained. He has tested its output all is good. I'm still hopeful to get her in the water a few times this year before it gets too cold. But winter here is pretty mild so I'm not worried about getting some seat time. I'll let you know when she makes some noise

[hydrasports cc]

This morning I sent the shop an email asking about the general condition of the block in regards to corrosion and water passage ways. It wasn't going to change the path forward because I'm already over the falls . Anyway the mechanic wrote me back saying he did a descaling of the block he said there was " partial " blockages that he cleaned up. Also descaled the head, thermostat housing area and whatever else needed it. He said the aluminum that Yamaha uses is much better than Johnson and Mercury. In his opinion he stated this motor should run for many years with no issues. Made me feel good about the path chosen.

[hydrasports cc]

Almost two months to the day I'm picking her up tomorrow ! Mechanic has had it out on the lake several times to break it in he says it runs very strong. Said it still needs 3-4 hours run time before opening it up full throttle but he did a few 40 second bursts at full throttle. No funny noises all seems good. I can't wait to get her on the water