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Weird noise on turn

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    Posted: September-10-2005 at 2:28pm
Boy am I glad I found this forum...
What a wealth of reading material here.

I cannot seem to find anything via the search on this topic so maybe someone can point me to a thread that has handled this already or give me someinsight.
I justpurchased a '78 SN with the 351 Commander. The boat is in really nice shape although the top end on the motor probably needs to be gone through but here is my question...
At cruising speeds the boat makes an odd kind of moaning sound when you turn. It starts out fairly loud and then fades away as the turn progresses. Could this be strut bushings or perhaps normal hull noise or something else? I also noted the other day after running around for an hour or two I was sitting at an idle and had a bit of a whining sound coming fromt he engine compartment. I had no idea what it was although the first thing that struck me was the transmission but I immediately shut off the motor. I then opened the cover and checked eveything but all seemed fine (including oil levels). I then went to restart the engine and when i turned the key there was nothing. Did this for a few times and then thought maybe I would have to tap the starter and the next time I turned the key (sitting for 5 minutes) it cranked back up and the whine was gone. Could this be a starter issue where it may have stayed engaged? Didn't sound like it was cranking just a whine. Anyway, sorry fo the long post and thanks for your help.
Central Oregon
'79 Ski Nautique
'84 & '85 MBZ Diesels
'79 Apollo 3000DB
It doesn't need to run bad or look bad just because it's old!
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The Lake View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote The Lake Quote  Post ReplyReply Direct Link To This Post Posted: September-10-2005 at 3:16pm
I had some noise during turns with my 69 SN. I changed the trans oil, which was a little low, and once the new Dex III was in it has run great, not noise.
Don't know about the starter issue.
Walk on Water
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69 Ski Nautique
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captan1 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote captan1 Quote  Post ReplyReply Direct Link To This Post Posted: September-11-2005 at 11:39pm
That's funny, my girl friend and I know of this noise, not what cause's it but it's kind of a water turbulence noise to me, I think it's the fact that the struts have a one strut gap, only two and far apart.

Don't worry, it's one of those noises you don't hear everywhere on the boat or all the time.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AWhite70 Quote  Post ReplyReply Direct Link To This Post Posted: September-12-2005 at 1:13am
My '79 Nautique makes the same noise. I've been told it's normal and that all of the pre '82 hulls do it. I have not however heard what the real cause is. Here are a couple of theories I've heard:

1. The sound is created by the way the water goes over the tracking fins in a turn and that the newer (post '82) 3-fin boats fixed this.

2. Something related to the prop being too far behind the strut and stress is being put on the strut bearing.

3. Some other theory related to prop, rudder, and strut placement, that I can't remember the details too.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fisherman Quote  Post ReplyReply Direct Link To This Post Posted: September-12-2005 at 12:47pm
Thanks for the quick responses. We just did the title exchange onthe boat and as i turns out it is in fact a 79 not a 78 as the PO thought.
I was thinking the same thing about the tracking fins being the cause. Glad to hear it is not just my boat...
I found the other issue too with the starter. Appears to be the ignition switch. I think it is just getting worn.
Where would a guy get a new switch?

One other question too about this year SN. My engine appears to have a 180 degree thermostat installed but the manual says it should run on a 140 for a raw water system. Any input? Do your boats run 140 or 180 thermostats? Also it seems to be a cold blooded engine as it doesn't like to just jump back into action after it has been off for say 15 minutes or so. Are your SNs like this too?

Thanks again,
Mitch
Central Oregon
'79 Ski Nautique
'84 & '85 MBZ Diesels
'79 Apollo 3000DB
It doesn't need to run bad or look bad just because it's old!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AWhite70 Quote  Post ReplyReply Direct Link To This Post Posted: September-12-2005 at 3:30pm
The OEM thermostat is 143 deg, but SkiDIM (and I think PCM) now recommend 160 deg. Apparently 143 deg stats didn't allow the engine to get warm enough to cook the water vapor and volatile hydrocarbons out of the oil.

I put a 160 deg stat in my '79 and it runs just above the 160 deg. mark when underway. When the engine is started after being off for a minute or two the gauge will read ~180 and then drop to 160.

For what it's worth most new engines come with 160 deg. stats these days
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Post Options Post Options   Thanks (0) Thanks(0)   Quote hyper1685 Quote  Post ReplyReply Direct Link To This Post Posted: September-13-2005 at 7:59pm
i have an 86 sn that makes the same noise. i though it was the trany. changed the fluid and it didnt help. then i thought it was the strut bushing. changed that and it didnt help. i hope it is just hull noise.
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