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Old 07-01-2023, 23:46   #1
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2 stroke outboard partial seize

My Yamaha Enduro 15 (2 stroke) is only 2 years old. It was used daily until about 6 months ago when I stopped cruising and did some freelance work. When I finally remembered that I should have been running it regularly (I was mainly thinking of salt in the cooling system) I found that it was impossible to turn-over. Fortunately I was able to free it up gradually, after removing the recoil starter housing. When it started, there was a nasty 'squeal' which worried me but it settled down ok.

I thought I'd had a lucky escape from an expensive rebuild, but now I find that the same problem recurs after a few days of non-use, despite using a 'rich' 2 stroke mix. As far as I'm aware, the only moisture getting inside would have been through the 10% ethanol which is added to all gasoline here. Even if moisture had caused some internal corrosion during several months of non-use, why would this keep occurring, and what should I do about it?

I won't be back at anchor and running the dinghy daily for another 6 months at least, so I need to be careful not to lose a fairly new engine..
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Old 08-01-2023, 00:12   #2
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Re: 2 stroke outboard partial seize

Chris, that's disappointing. I wonder if the bore or pistons has been damaged.

How do you feel about taking the cylinder head off for a looksee? The other thing you might try is to borrow a compression tester to see if one cylinder is down.

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Old 08-01-2023, 01:11   #3
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Re: 2 stroke outboard partial seize

Sounds like bearings. Try listening to a screw driver pressed against various parts of the engine. If the noise is oscillating then probably the pistons, see above compression test, if continuous it is more likely the bearings. 2 strokes relay on the oil in the petrol to lubricate the bearings if this is allowed to evaporate it can go gummy especially bio fuel. You could try a healthy does of carb cleaner to see it it breaks down any gum.

2 strokes are really really easy to take apart and fix so no big deal to have a look inside. Continuous screeching my money is on the bearings.
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Old 08-01-2023, 04:09   #4
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Re: 2 stroke outboard partial seize

Ethanol is hydrophilic. Water and ethanol are miscible; so ethanol will carry water through the fuel system as part of the mixture.

However, it cannot carry unlimited quantities of water. Condensation could quickly overwhelm the property of ethanol to remain in solution with gas and carrying water.
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Old 08-01-2023, 04:14   #5
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Re: 2 stroke outboard partial seize

Check the water pump impeller.
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Old 08-01-2023, 12:13   #6
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Re: 2 stroke outboard partial seize

Try spraying fogging oil into the inlet and hand crank it over. If you can get fogging oil (Stabil makes a good one) use ATF thinned 30% with oil based paint thinner or use Marvel Mystery Oil. Seafoam Motor Treatment is also a good choice. I suspect you either have crud on the rings and bores or possibly a bearing issue. High detergent oil (like MMO or Seafoam or ATF) will help either.
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Old 10-03-2023, 21:39   #7
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Re: 2 stroke outboard partial seize

Thanks for the helpful suggestions. I thought it might be useful to follow-up and ask a more general question about flushing of outboards whilst cruising!

I opted for a professional rebuild and it turns out that the problem was entirely a result of my lack of flushing. The photos show the "Oil seal holder" at the base of the engine block. Although that's the official name of the part, it is more like a casing for the drive shaft (cut into 2 pieces by hacksaw in the photos). I'm not sure what the bottom end looks like, because it had crumbled away, due to salt damage inside the holder/casing. It's not clear to me why there is seawater (and hence salt crystals when dry) inside here but it is very clear that flushing with fresh water is essential to avoid similar problems.

And so to the general question - There are many threads on CF about dinghy hoisting; use of davits; whether or not to remove outboards when on passage, etc, but I've not seen any threads about flushing outboards. Surely I'm not the only one struggling with this? With my 9ft AB on a 40ft cat, I cannot start the engine with the dinghy hoisted, even if I could rig a bucket of fresh water under the engine lower case.

1st question - if the dinghy is used daily, is it ok NOT to flush? This has been my experience over the last 10 years, mostly with my previous Tohatsu.

2nd question - if the outboard is left unused for a period, after how long does it become essential to flush in order to avoid salt crystallisation? 1 week? 1 month? I suppose this might vary according to climate..

I was about to conclude by saying "this has been an expensive lesson for me" but thanks to the shockingly low labour cost in the Philippines, I paid only US$100 for labour and US$400 for Yamaha OEM parts.
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Old 25-03-2023, 01:32   #8
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Re: 2 stroke outboard partial seize

To quote Oscar Wilde "The one thing worse than being talked about, is NOT being talked about".

At the risk of abuse from members who have kindly 'zipped' mouths, thinking "If this guy doesnt know how to flush an outboard when it's hoisted on davits, he should not be cruising..", I just want to try one more time.

o If the outboard is used daily, is this sufficient to prevent salt crystallisation?

o If not, how often do you flush with fresh water, and how do you achieve this while cruising?
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Old 25-03-2023, 03:08   #9
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Re: 2 stroke outboard partial seize

https://yamahaoutboards.com/en-us/fe...g-with-steve-p

I'm in the States so can't see any Yamaha two stroke version. There's a couple of ways to do it. The best is as above without running the engine.

Another is to use "ear muffs" and run it. Another is to put the lower end in a bucket and run it.

If you don't have a hose and pressure water a 5 gallon pail with a manual or electric pump will work. Yahama had a service bulletin about 13 years ago that showed a 5 gallon pail and cheap drill type pump. They recommended back then I believe every 25 hours of running. If you have pressure water on board rig up a hose. There are adapters for faucet to garden hose. The flush fitting on the motor is female garden hose fitting.

Running it every day helps but will not prevent salt corrosion. If yours rusted out that fast I'd flush often. did anyone check for or change the zincs in the engine? There should be two? Not the skeg but there should be one in the block and possibly one in the head. If your thermostat is bad that will let salt precipitate out of the water at anything above around 178*F. Might be worthwhile to check it.
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Old 25-03-2023, 03:39   #10
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Re: 2 stroke outboard partial seize

Quote:
Originally Posted by chris in SG View Post
o If the outboard is used daily, is this sufficient to prevent salt crystallisation?
Not in my experience.

Pull up a sail bag, here's the story.

After a fortnight of camping cruising on my dive rib including crossing the English Channel, I lifted the boat out on to the trailer and flushed the Yam 115hp v4 2 stroke.

The following day set off to stay in a caravan with my folks on the upper reaches of the river Thames. Took the rib and we spent a week motoring up and down the clean fresh water river.

Finally back home and time for a service. However, on taking the thermostat out I was astonished to see it covered in salt crystals, despite perhaps 20 hours of use in clean fresh water.

So, if you flush straight away after use it will remove saltwater. However, in a warm engine, if that saltwater is allowed to evaporate and leave salt crystals behind, they won't then dissolve even if flushed with more freshwater and the engine being used at operating temperature for some hours.

The only thing I can think of for an outboard is to use that Volvo Penta flushing liquid or something like Rydlyme.

https://rydlymemarine.com/product/po...-flushing-kit/

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Old 25-03-2023, 17:19   #11
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Re: 2 stroke outboard partial seize

Thanks guys, very helpful comments and rather sobering. Unfortunately the Yamaha Enduro 15 (2 stroke) does not have a flushing port. Perhaps this design is being phased out and flushing ports are a new idea? The next time I need to buy an outboard, a flushing port will be high on my list of priorities.

I did buy 'ear-muffs' but the difficulty is running the engine with the dinghy on davits. I will now try again, with the dinghy in the water and the ear-muffs submerged. It occurs to me now that even if the muffs don't seal perfectly, the positive fresh water pressure should prevent seawater from contaminating the flush.
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Old 25-03-2023, 17:31   #12
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Re: 2 stroke outboard partial seize

You can use a bucket for the fresh water and run the engine and not worry about contamination.
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Old 25-03-2023, 19:53   #13
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Re: 2 stroke outboard partial seize

The community I live in is salt water access only. We all use outboards of various makes and age. None ever see a fresh water flush. some are 15 to 20 years old. I have a Suzi 90 4stroke on my commuter, it's seven years old, never seen freshwater (except rain) kept in the water 27/7/365. Used nearly every day, as are most commuter outboards.
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Old 07-04-2023, 04:06   #14
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Re: 2 stroke outboard partial seize

Quote:
Originally Posted by Bruce K View Post
The community I live in is salt water access only. We all use outboards of various makes and age. None ever see a fresh water flush. some are 15 to 20 years old. I have a Suzi 90 4stroke on my commuter, it's seven years old, never seen freshwater (except rain) kept in the water 27/7/365. Used nearly every day, as are most commuter outboards.
This would be what I would expect to be the experience of 99% of OB users.

Sure, it would be nice to flush the engine after each use, but I'm shocked that many people are having trouble from not doing so.

I have a 22 year old Tohatsu 30 two stroke that rarely gets flushed, and is used sporadically. (FWIW one of my first ebay purchases 20 years ago was a kit someone sold that back flushed with flowing water thru the pee stream hole. After further study, I finally concluded that I may have been flushing only the water pump, so finally removed the kit.)

I've never had a problem, but maybe I should be prepared this Spring.
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