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Donza
07-07-2008, 12:03 PM
G'day.

The ol'man purchased a new Yamaha CV30 under 3 years ago. He doesn't get out that often but when he does everything seems to turn pear shaped. Just wondering if anyone had any problems or if anyone can help us out with some more info on this motor.

Here's the background:

He purchased the motor from a pretty big dealer in country Vic. and was told when he bought it that it would be fine to troll with. We try to get up to Dartmouth at least once a year so being able to troll is a must. We followed all instructions from the dealer in regards to running it in (first two tanks at 25:1 then 80:1), kept up with all the services etc. Last July we headed up to Dartmouth (the first 5Lt of oil still hadn't been used) and on the first day we noticed that the motor was running pretty rough. On the second the bottom plug fouled. We changed it and it ran fine for about 1/2 a day. Then it fouled again. On the third day we'd had enough and headed back to the ramp. The motor got to within 9kms of home before breaking down completely. After a 3km row in near freezing conditions two top blokes towed us in. They had a bit to say in regards to the ratio.

We took the motor back to the dealer and he told us that the motor was fine, there was nothing wrong with it, it was only because we were trolling (which he now informed us we shouldn't be doing with this motor). He then told us we should be using a 50:1 ratio. They also put in some hotter plugs. Even after all this the motor still runs pretty rough with a destinked flat spot when accelerating and there is a lag of about 2-5 secs when switching the motor off.

When up and really going the motor runs reasonably well but every now and then you can feel the motor slow slightly then take off again like a cylinder is struggling a bit.

If you can help us out that would be great.

Cheers

Donny

Mark-P
07-07-2008, 04:52 PM
Mate i had a 25cv a few years back, the mix i used was 100:1 .....
The problem with trolling with mine was 2 cylinders one carby ....
And remember cv stands for customer value, so shes nofrills .....
The fact that its oiling up would probably be the mixture your running !!!

Mark

Skusto
07-07-2008, 05:00 PM
as mark said above mate our old 30 yamaha used to run at 100:1 as well have a look in your handbook and it will clearly say what u should be running the engine at. cv i customer value u did get the bottom end of the yamaha range if u really do alot of trolling a 4stroke is the only way to go any 2 stroke hates trolling unless u go the new di 2stroke. have u thought about gettin a electric motor for trolling assumming your talkin about estuary trolling we down it on our last tinnie as the 30 yamaha was just no good for trolling.

pedrodepacus
07-07-2008, 06:13 PM
just a idea i think you said it was a fair while beetween trips did u renew the fuel i dont no just a thought

tim2
07-07-2008, 06:24 PM
I had a yamaha 15hp, and it said to run it at 100:1 but when i got it serviced the mechanic told me to make sure i run it at 50:1 or it would gum up.
It ran with absolutely no problems no matter what i was doing. I trolled, crabbed and ran it flat out.
Actually i still have it, havent used it for 2 years other than getting my old man to run it to keep the impellar ok and it still runs great, gotta sell it with my old 3m tinny.

Mark-P
07-07-2008, 06:40 PM
[quote=tim2;856609]I had a yamaha 15hp, and it said to run it at 100:1 but when i got it serviced the mechanic told me to make sure i run it at 50:1 or it would gum up.

Not having a go at the mechanic, but 50:1 means more oil !!
Wouldn't that make it gum up more so than 100:1 ??

Mark

Spaniard_King
07-07-2008, 07:24 PM
No 2 stroke carby engine should be run at less than 50:1.. 100:1 will kill it.

Personally I think you may have 1 piston that is partially seizing. Once you do cylinder wall damage you will get more friction in that cylinder and hence more heat causing the piston to grow more with the heat reducing the tollerances.

get a compression test done.

A good mechanic will have a light to enable internal inspection of the cylinder bore without removal of the head.

Mix and only use 50:1, get the engine tunned to this mixture. Anyone worth there salt will be able to tune this engine to run all day at idle without plug fouling.

Have the engine thermostats checked to ensure correct cooling /runing temps are being acheived.

Mark-P
07-07-2008, 07:43 PM
Hey garry, the sevice manual for my yammy said 100:1
Does that mean i was doing damage ??

By the way , i ended up with a transom mount tranny ...
recommended by haines !!

Mark

Skusto
07-07-2008, 07:47 PM
No 2 stroke carby engine should be run at less than 50:1.. 100:1 will kill it.

Personally I think you may have 1 piston that is partially seizing. Once you do cylinder wall damage you will get more friction in that cylinder and hence more heat causing the piston to grow more with the heat reducing the tollerances.

get a compression test done.

A good mechanic will have a light to enable internal inspection of the cylinder bore without removal of the head.

Mix and only use 50:1, get the engine tunned to this mixture. Anyone worth there salt will be able to tune this engine to run all day at idle without plug fouling.

Have the engine thermostats checked to ensure correct cooling /runing temps are being acheived.

i can only disagree on that we had our 30 yammy for about 5 years running at 100:1 and neva one problem. yamaha say to run it at that and thats what we did and neva had one thing wrong with it. over those 5 years it would of been out at least every 2nd wkend if not more. so it had its use. im pretty sure to the 30 oil injected and up all run at 100:1?

Spaniard_King
07-07-2008, 08:45 PM
Hey garry, the sevice manual for my yammy said 100:1
Does that mean i was doing damage ??

By the way , i ended up with a transom mount tranny ...
recommended by haines !!

Mark

Mark IMO yes you would be slowly killing it. The main reason being its a splash lubrication system.. the less oil you use the less lubrication you get.. 50:1 being the optimum ratio for carby engines DI.. totally different system.

Skusto, all I can say is you must be one of the lucky ones.. there is little to no difference on quality of the internals on most carby engines.. why should yamaha run better on 100:1 than a Johno or merc... OMC did try it but changed it very quickly.

tim2
08-07-2008, 07:57 PM
[quote=tim2;856609]I had a yamaha 15hp, and it said to run it at 100:1 but when i got it serviced the mechanic told me to make sure i run it at 50:1 or it would gum up.

Not having a go at the mechanic, but 50:1 means more oil !!
Wouldn't that make it gum up more so than 100:1 ??

Mark

Yeah, that would be my mistake not the mechanic::) But he did say to run it 50:1 not 100:1 and no problems ever.

tin can marlin
08-07-2008, 09:07 PM
They are a great little motor but they are very basic ring wade wimmers he will sot it out.