Posted on 11/09/2014 4:23:52 PM PST by Blueflag
We are looking for advice regarding Yamaha 2-stroke engine for their (older) line of personal watercraft- say 2002 - 2007; pre-four-stroke motors. We want to buy two used ones (the full watercraft, not just the motors), and don't know how to gauge the hours of use on the Hobb's meter. How many hours is too many? What if the cost of a rebuild? How do you know it needs a rebuild? IF this was about chainsaw motors, I could answer my own questions. Looking for FReepers with experience with Yamaha PWC.
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If they have been run every year (takes care of the dried out seal issue), figure 700 to 1000 hours for a fresh water run PWC. YMMV, but this is what has been recommended to me from a good guy, who knows his stuff. Pumps are another matter. Sand and/or debris can do a fair amount ($$$) of damage. Also try to rock the engines back and forth. If the motor mounts are gone (common) figure on more $$$ for pump rebuilds. If the motor can move, it won’t align the pump and you will be buying pump shaft and seals for sure.
On the two stroke upper cylinder compression tests (these are singles), we always remove the plug, put the plug cap back on the plug, ground the plug, and kick over with the throttle held wide open. People have different practices regarding warm vs. cold motors -- just be consistent.
You can find Youtube videos showing leakdown tests -- they aren't that difficult. I've actually never bothered to do one.
Check this out: https://answers.yahoo.com/question/index?qid=20080217062509AAko0kv
Dave M has given you some good advice. In the United States the average seasonal useage for a PWC (Personal Water Craft) is 50 hours, 300 hrs is a 6 year average. Also, determine the actual year on manufacture by looking at the VIN on the right rear of the unit, last two numbers is year. If the units were used in salt water be extremely careful of errosion and rust. ALWAYS have a used unit checked by a qualified tech for that manufacturer.
Being able to wrench meant I always had a ride and even though chick’s dads usually hated me, they became my buddy when they found I could fix their car...
Me too, but that was because I owned a '64 Mini and had to do all the work myself. Got to the point where I could pull the engine in 55 minutes flat.
Let em sit dry for a year and get back to me heh heh. The absolute worse ones were the Kawa triples, I think if you didn't start em once a week they'd stop running out of spite; but man they could haul the mail in a straight line and that was stock, add chambers and the correct jetting and they would scream except you could walk faster if it was below 6k rpms.
They’ve gone much longer than that — sat unused for as long as ten years.
I’m restoring a new-to-me Suzuki TS185 right now.
That’s pretty amazing, did they have oil in the tranny? I had a YZ250 I let sit a long while and while it ran, it fouled the plug because it was sucking in the gear oil, of course I didn’t get it new so who knows how bad it was abused before I abused it too.
I’m afraid that one day, as someone already mentioned, the PTBs are going to ban two strokes not only on lakes but everywhere.
I've seen more than a few pistons with the crown holed from careless mixing.
I agree. Compression test is the first place to start.
I had a 70 H-1. I know EXACTLY what you mean!
brass rod is a cheap source of shear pin material. I have an ancient 7.5 hp air cooled outboard and shear pins are produced with brass rod and a saw.
Bolt cutters also work but sometimes the ends need a bit of a touch with a file if the shaft hole is a tight fit to the rod.
” Got to the point where I could pull the engine in 55 minutes flat.”
What brand heavy duty zipper did you use?
Or is there a super dooper Velcro I haven’t heard about?
Alas, I am no stranger to something like that "African Queen" sequence where Humphrey Bogart has to make a propeller in the jungle. Hint: Wooden mallet is best. Easy on the heat. Hump was working with iron.
In future, FReepers, refer all mechanical guru type questions to well ... a a a like, you know, guru. Take over GG!
Perhaps, just maybe - iffn you hadn’t used 180,000 psi steel rod when that piece of brass rod was hidin’, meybe the pin might not have kept on a grindin’ ‘til only the maufacturer and you knew which size that prop was when it left the factory.
Humor aside, the 7.5 air cooled could operate without the water pump retaining its vanes. All it did was pump enough water to keep the lower crankcase sear from reaching thermal destruction. It was a nice motor for pushing a flat bottomed canoe through the shallows west of Cockroach Bay.
Noisy, but could push through mud, algae, assorted ancestral habitats of Democrats.
Generally if it's the rings you could tell by doing a compression test dry, then repeating after pouring a tablespoon of oil into the cylinder and turning it over a few times. If the compress increased after you put the oil in, that was a good indication the rings were shot.
Worn-out valve guides usually produce a lot of smoke at startup.
True.
I don’t think that’s really high usage. I have two Yamaha jet skis that i use hard. Ones over 200 hours and the other is over 400. Both supercharged and over 9 years old.
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