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Yamaha powerhead break in questions

Old 05-02-2017, 01:01 PM
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Default Yamaha powerhead break in questions

I recently rebuilt the powerhead on my 1997 Yamaha 150 ProV. I am currently in the break in process and had some questions...
1. I've stopped after 4 hours of break in trying to fix a leak in the bleed system. I haven't had boat out in a week. Is it okay for the break in process to last that long or do you want to get it all done in a few days?
2. I did a compression test on the motor today and all 6 cylinders were 87-88 PSI? I don't think it was fully warmed up, but would that change that much?
Old 05-02-2017, 04:04 PM
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We're you reading the gauge correctly? ??
Old 05-02-2017, 04:40 PM
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yeah, not sure if I tested correctly but I read the gauge correctly
Old 05-02-2017, 05:10 PM
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Rings, rings...it's all about seating the rings. Open up the throttles and build cylinder pressure. Force those rings outward against the cyl walls. Just don't run it at full throttle for extended time. Bring it back down and open it up again. Repeat until you get bored. I hope you didn't baby it during those first 4 hrs. The window of opportunity is not that wide. After the honing peaks wear down, ring seating is reduced dramatically.
The engine doesn't care if you do it in one day or one month. A good warm-up and put the hammer down.
You will end up with a better sealing chamber.
Old 05-02-2017, 05:25 PM
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oh man, that makes me feel better...hopefully I have this leak taken care of and I'll run it hard tomorrow. I've been following the break in procedure so not babying it. It won't go past 5000 rpms though is that a red flag at this point?
Old 05-02-2017, 06:19 PM
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What max RPM did you get before the rebuild? As noted above, break in does not have to be completed in a set amount of time, but the advice to run it fairly hard is prudent. Get the rings seated properly, and you won't have to deal with issues like making oil later on.
Old 05-02-2017, 07:39 PM
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yeah I bought the boat with a bad cylinder so I had nothing to go on as far as how it should run.

Update...Earlier tonight I decided to look at the linkage and noticed when my son put the cockpit throttle to the floor the butterflies were only opening about halfway. Shouldn't the butterflies open fully when the cockpit throttle is wide open?

I'm wondering if that's my low rpm issue.

and if so have I compromised my break in procedure by no using full throttle during the first 4 hours?

thanks for all the help

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