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| RPM and Speed on a 2002 348 https://www.smwebhead.com/phpBB3/viewtopic.php?f=6&t=8334 |
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| Author: | summarays [ Sat Sep 03, 2011 7:53 pm ] |
| Post subject: | RPM and Speed on a 2002 348 |
Hi guys, Things are going well on the boat, getting used to it and docking it has been great so far. Recently (the past two times out) I have noticed that my engines are sounding a little louder than normal (not much) but when I am cruising, I am running around 3500 RPM and doing only about 18-19 knots. The seas were a little rough, not that bad and I only had about 4-6 people in it (two of them small children). Seems like from the specs, I should be doing more than this. When I first purchased the boat a couple months ago, I had it at 3500 RPM and doing easily 25-30 knots. Is there something up with perhaps my trim? Propellers? Just doesn't seem right. My oil, temp all seem normal, just thinking something may be a little off. Any thoughts would be appreciated. |
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| Author: | summarays [ Sat Sep 03, 2011 7:59 pm ] |
| Post subject: | RPM and Speed on a 2002 348 |
[merged from other posts, duplicates not needed] |
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| Author: | aguyindallas [ Sun Sep 04, 2011 1:24 am ] |
| Post subject: | Re: RPM and Speed on a 2002 348 |
I would be sure both drives are lowered all the way when you take off. If they are trimmed up, your props may be cavitating and causing the speed loss. |
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| Author: | summarays [ Sun Sep 04, 2011 5:44 am ] |
| Post subject: | Re: RPM and Speed on a 2002 348 |
I have inboards. Any other thoughts? |
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| Author: | wkearney99 [ Sun Sep 04, 2011 7:02 am ] |
| Post subject: | Re: RPM and Speed on a 2002 348 |
Slime or growth on the bottom would slow it down and thus make the engines work harder. I get mine cleaned by a diver once a month around here. |
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| Author: | Turtle [ Sun Sep 04, 2011 6:25 pm ] |
| Post subject: | Re: RPM and Speed on a 2002 348 |
The maths says that if your Motors are turning at 3500 revs and you haven't changed your props than you need to look for other variables. Weight, Slime, barnacles on the props (will make them cavitate) and rough conditions. Full tanks vs nearly empty ones can be a 600kg (1000lb) weight difference. Probably not any one thing but a combo of a few with weight being a prime suspect I would think. While you dont have legs I think you would have Trim tabs and they will always make a difference. Next time in good water get up to speed and adjust the trim tabs and bury the nose and see what happens to to your speed/revs. So you load up with few people (500lb) add some extra fuel which is sensible( 500lb) add the junk we all bring and the day is rough. Pretty sure you have nothing to really worry about, you've just hit real world boating. ...But do clean your bottom and props!!! happy boating Steve |
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| Author: | summarays [ Sun Sep 04, 2011 7:50 pm ] |
| Post subject: | Re: RPM and Speed on a 2002 348 |
Thanks Steve, appreciate the comment. I went out today with 11 people (8 of them kids) and the same thing, nothing major but it does seem that I might have some barnicle growth on the boat and maybe the props as well. I am going to get a diver out there this week and clean it and see what that does. Thanks! |
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| Author: | wkearney99 [ Mon Sep 05, 2011 6:55 am ] |
| Post subject: | Re: RPM and Speed on a 2002 348 |
As for growth on the bottom, if you see barnacles you are NOT cleaning it often enough. Barnacles won't grow until slime has already been growing there for a bit. At least not on the hull bottom. One drives and props it varies, but seeing barnacles is a sure sign scrubbing needs to be happening more often. |
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