boat slowing down

Bobg · June 30, 2015, 03:08:57 PM

I have a 25xp in my catalina 34, I used to max out at about 5.5 -5.7 knots at 2500 rpm, never had I hit 6 knots I repitched the prop from 15/9 to 15/10 last year gained about .2 knots, this year I am lucky if I can get 5.4 knots at 2650 rpm in calm water, I have checked the rpm with a hand held lazer tack, sail in lake superior in clear clean water. could it be clogged filters? I changed them last fall and only use clean fuil, tank is full .. I read in archieves some of you get 6.5 to 7 knots from the exact same boat I have. any ideas?

KWKloeber · June 30, 2015, 04:00:05 PM

have you checked your bottom?

Carolina Soul · July 01, 2015, 03:16:41 AM

Could you have fishing line or other such debris wrapped around your prop/shaft?

Paulus · July 01, 2015, 03:52:17 AM

I had the same issue but not being very mechanical and mostly sailing, I did not give it much thought. Last summer it started going even slower. The transmission was slipping. Had it rebuild and the boat runs at 5 to 6 knots.
Torresen recommended that I not only check for level but color. They also recommended changing the transmission oil every season.
Paul

tommyt · July 01, 2015, 09:13:17 AM

Paul,

North Channel this year?

Bobg · July 01, 2015, 06:02:14 PM

bottom clean, just splashed boat 3 weeks ago, no fishing line, changed transmission fluid last year, hope that is not the case,, fluid looks good this year, i dunno, got me confused, whoud like to get at least 6 knots like eveeryone else. is there a good way to check transmission?

Stu Jackson · July 01, 2015, 06:16:06 PM

Quote from: Bobg on July 01, 2015, 06:02:14 PM
is there a good way to check transmission?

Bob,

Have you checked the C34 Tech wiki, Engine? There is a section for transmissions and a PDF of a Universal bulletin to how to check your transmission.

Did you fill the transmission with fluid for the winter and then remove most of it to the right level in spring commissioning?

Also, what are you using to check your speed?

Roland Gendreau · July 01, 2015, 07:00:08 PM

So why is the engine not going beyond 2650 ? Mine will hit 3200 or so with a 2 blade flexofold.

Are you sure the throttle cable is fully opening the throttle?

patrice · July 02, 2015, 06:48:41 AM

Hi

Question, with what do you check your speed ??
with the log or a GPS, might be your log is not calibrated ?

Clay Greene · July 02, 2015, 11:44:35 AM

Further to the last, it could be some mechanical obstruction or damage to the impeller in the speed transducer if that is the basis for the speed calculation.

Bobg · July 02, 2015, 11:58:17 AM

the boat is checked with gps, and other boats going along side of me, i said the 2650 rpm, because i don't like reving the engine to max speed, and boat used to go faster at that rpm. I get little increase in boat speed at 3200 or so rpm, And no I did not fill the transmission before winter lay-up, I didn't see that in the manual. I will check the manual on how to check transmission, ( thanks stu, and all the others.) and the prop is ok and clean. sure got me baffled, hope it isn't the transmission but it is looking more like that may be the case, fuel filters? hopefully, will change them next time at the boat, but i am pretty sure they are clean Thanks all

Ken Juul · July 02, 2015, 02:48:21 PM

have you added any weight to your boat? When the boat was new to us, easily got 6-6.5 knots from a 10 pitch michigan sailor. Now with the dingy, Admiral's needs, boat toys, etc it's is usually in the 5.5-6 range. Fully loaded going south for the winter, I was happy to motor at 5.

KWKloeber · July 02, 2015, 03:02:23 PM

Quote from: Bobg on July 02, 2015, 11:58:17 AM
sure got me baffled, hope it isn't the transmission but it is looking more like that may be the case, fuel filters? hopefully, will change them next time at the boat, but i am pretty sure they are clean Thanks all

Won't be the engine/fuel end, if you are doing the RPMs you say. If you can't hit the RPMs, then look to sources, but so long as you are getting shaft RPMs, then it;s past that point. Is your Tach accurate? They do go bad.

ken

Ron Hill · July 05, 2015, 04:45:48 PM

Bobg : If your RPM are the same, with a clean bottom (& clean under the wing!!) and if you put your Xmission in gear and cannot turn the shaft by hand -- I'll guess the you've loaded some extra "stuff" like Ken mentioned!!

A thought

RV61 · July 16, 2015, 04:15:47 AM

When I could not hit max RPMs after checking many things found the "Mystery Filter" in old Electronic fuel pump. Cleaned filter and boat has run great 6.2 on flat lake on Erie.