Thread: Lost RPM's, Any Ideas?
07-08-2008, 09:13 AM #1
Lost RPM's, Any Ideas?
On saturday was turning 8120-8140 full tank of gas all day.
Temp was 90*, water 80*
Actually thinking of going to a bigger impeller to drop rpms down just
a hair because was over 8200 when it was cooler out.
On sunday, max rpm's 7810 and dreamometer wouldn't even
get to the 70 max. Usually hits this way before max rpms and even at
steady 90% throttle.
Air temp was 98*.
Could the extra 8-9* temp increase cause this loss????
Should I look for something else causing this..
Secondary problem, starting taking on water noticed on saturday.
No lake water leaking thru intercooler / exhaust hoses while testing
on garden hose so I filled hull with water.
Found water dripping from back of pump, due to angle..
No water dripping forward by intake grate/ drive shaft seal area.
Took out seats, etc to look for air bubbles, found slight air
bubble coming from pump tunnel on top where there is a fiberglass
seam.. Very slight.. My electric bilge pump would kick in when
idleing around cove slowly.. Never when just sitting still tied on
to boat by itself and never when out at cruising speeds...
07-08-2008, 09:22 AM #2
Check to see if the nose cone on the prop has slid up the shaft some. If so, it is holding your driveshaft in towards the motor a little and not allowing the carbon seal to work effectively. If this is the case, install a solid front motor mount to keep your motor from flexing backwards during acceleration (which pushes the driveshaft into the pump splines and pulls off the nose cone when you let off the gas).
07-08-2008, 02:48 PM #3
Thanks for the suggestion WOT..
Does anyone think that poor fuel quality could
cause a loss of rpm's ..
On sunday, I filled up at a not so trustworthy gas station..
The ski pulled/accelerated normally until about 7500 rpms,
then takes forever to get up to 7800
In the past (saturday) it pulled real hard up to 8020, then just
took a little time to squeeze the last 100 or so out of it.
07-08-2008, 04:23 PM #4
07-08-2008, 04:29 PM #5
- Join Date
- Oct 2005
07-09-2008, 08:58 PM #6
Update on Problems!!
Took a closer look today. I removed intake grate and "moved" drive shaft. I thought it should have Zero play in it.. Had just a little.
I removed pump assembly. Billet Solas nose cone was NOT screwed (reverse threads) into front of 13/18 prop. Wear ring has slight damage (don't have a new one right now, so this will due!).
Put in 13/19 used prop that looks new from board member with nose cone PROPERLY INSTALLED. Want to try this prop since when cooler I'm over 8200 rpms. Would like to drop rpms when running properly to 8100 at WOT.
\PUT everything back together... NO SLOP IN DRIVESHAFT AT ALL NOW..
Thanks for the suggestion on checking nose cone!!!!
Never would have thought of that.
Like I stated originally only leaked water when IDELING. never sitting still or out at cruising speeds.
I won't have a chance to ride for 10 days or so to see if all is good now. I will update when go for test ride.
The only other isssue I have is that my drain plugs are not draining.
I pulled them today as well.. They have a vacuum line attached on
1 side that is still intact with zip tie and other "side" is that funny
looking perforated check valve looking thing..
Never had 1 out before, so I hope this is normal..
Would my nose cone/ leak issue be related at all?
Thanks all. Spending faster than I can make It!
07-10-2008, 02:29 AM #7
07-10-2008, 02:25 PM #8
was at stealership this am for budds activation of my depth finder,
Had them look closely at drain plugs..
The white "stopper" inside has slid back not allowing water to
flow thru so They suggested I use a pick tool or something to
put the white rubber stopper back in its proper place.
07-19-2008, 09:51 PM #9
Update on RPM loss
Got To lake today with 13-19 prop installed with nose cone correctly.
Results: my electric bilge pump kicked on 2-3 times total.. Not every 5-10 minutes as last ride. So I still am taking on water, just a whole lot less. I'll try to look for another leak....
Bad news, could only get 7700 rpms consistently. Hit 7800 after 10 min. or so of riding but could not duplicate. The early 7800 run netted 66.5 gps while later 7700 netted 65.4 gps..
So , CRAP !!
I must have something else going on here. I'll check all hoses for boost leak and usual other stuff. I have the good T bolt hose clamps on my rubbers in S/C system.
What else should I look for????
07-19-2008, 10:06 PM #10
you may have a carbon seal going bad letting water into your hull..
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