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?
have you checked your bottom?
Could you have fishing line or other such debris wrapped around your prop/shaft?
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
Paul,
North Channel this year?
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?
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?
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?
Hi
Question, with what do you check your speed ??
with the log or a GPS, might be your log is not calibrated ?
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.
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
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.
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
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
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.
Rick : Sounds to me like you need to re-plumb the fuel line coming out of the fuel tank!!
Should be : Fuel tank to primary filter (Racor/Dahl) then to the electric fuel pump and then to the engine fuel pump!! (not tank to pump to filter!!)
Then there is no need to ever check the screen in the electric pump as it receives filtered fuel!!
A thought
bringing up a old post, my boat is still slowing down, I have checked the rpm with a hand held, the rpm's do registrar a couple hundred low, but all that being said, at 2200 on hand held, the boat can only get about 4.3 knots, I checked the prop shaft, it is registering 1100 rpm. I heard that it should be about half. or 2-1 ratio. The boat is empty of stuff, tanks empty except fuel, no dinghy, 2 people. I used to get about 5.7 knots on a regular basis. new filters installed.
Ron I haven't tried turning the shaft while in gear yet. can't seem to find where it says how check transmission in the wiki. lots of other stuff, but that. tranny fluid changed this spring looks good
I do see where the injection pump was the cause for one owner, looks like a pain to remove, do all the electric fuel pumps have a mystery filter? or screen.
under power I can get 3000 rpm, at dock out of gear, it will quickly get 3200 rpm,
I have 1000 hours on engine, any more ideas?, thanks guys. pulling boat this week for winter
Quote from: Bobg on October 06, 2015, 08:12:49 AM
bringing up a old post, my boat is still slowing down, I have checked the rpm with a hand held, the rpm's do registrar a couple hundred low, but all that being said, at 2200 on hand held, the boat can only get about 4.3 knots, I checked the prop shaft, it is registering 1100 rpm. I heard that it should be about half. or 2-1 ratio. The boat is empty of stuff, tanks empty except fuel, no dinghy, 2 people. I used to get about 5.7 knots on a regular basis. new filters installed.
Ron I haven't tried turning the shaft while in gear yet. can't seem to find where it says how check transmission in the wiki. lots of other stuff, but that. tranny fluid changed this spring looks good
I do see where the injection pump was the cause for one owner, looks like a pain to remove, do all the electric fuel pumps have a mystery filter? or screen.
under power I can get 3000 rpm, at dock out of gear, it will quickly get 3200 rpm,
I have 1000 hours on engine, any more ideas?, thanks guys. pulling boat this week for winter
Hi Could it be in your boat's NAME the issue ???
If the engine is running at same speed it was before and you used to get higher speed, then the trouble should be between engine and prop.
Like mentioned by .... with engine NOT running, if you put in gear, is the prop shaft locked ? can you turn by hand.
Or you will be able to check prop when out of water.
Good luck
Bob : All pumps have a screen installed by the manufacturer to protect the pump!!
Hi bob,
I don't think your issue is from a bad filter or something else with engine.
If the engine run at same RPM as before, and can keep it, then these option should be ruled out.
Now, it should be between the engine and the prop.
Imagine your car engine running at 2500 rpm and going at 60mph on the road, next day engine running at 2500rpm but doing 30mph. Are you checking the engine or something else?
In your case, it is a good chance that transmission is slipping, or that your prop got damaged by a debris in water. It does not take much for the prop to cavitate if not perfect.
Or I'm going for a long shot, but when you got the prop repitch, did you had good result after, or the issue is since that. Could be a not perfect repitch ??
I'm not an expert, but trying to find things to look for....
When we bought our MK ll in 2001, within the first year the boat would slow sometimes. I could see the shaft slow while watching it with the engine running at constant RPM. Dealer insisted it was shift connection on the transmission and adjusted it several times. Problem not solved. Transmission was removed from the boat twice and checked in a shop, who could find no problems with it. Seemed to work on the workbench. Put it back in the boat, still the same problem. Long and short of it, Catalina replaced the transmission. No more problems 14 years later.
Maybe a similar problem with your transmission?
Jack
C34 MK ll 2001, FK/TR M35BC
When I had the prop repitched from 9 to 10, my boat speed increased to around 5.8 knots, up from the usual 5.5 so it did help somewhat, Pulled the boat for the winter, had a friend try to turn the prop by hand while I secured the engine from turning over. he couldn't turn the prop while in gear,, if I didn't stop the engine from turning over he could turn the prop and the engine would turn also. Also when in the water, the transmission would turn at 50% engine speed, i.e., 2000 rpm on engine, 1000 rpm on transmission, all test seem to favor the fact the transmission is probably ok.. next time on the boat I am going to give the engine a compression test. and reflect all winter on what it is.
Quote from: Bobg on October 12, 2015, 06:22:53 AM
When I had the prop repitched from 9 to 10, my boat speed increased to around 5.8 knots, up from the usual 5.5 so it did help somewhat, Pulled the boat for the winter, had a friend try to turn the prop by hand while I secured the engine from turning over. he couldn't turn the prop while in gear,, if I didn't stop the engine from turning over he could turn the prop and the engine would turn also. Also when in the water, the transmission would turn at 50% engine speed, i.e., 2000 rpm on engine, 1000 rpm on transmission, all test seem to favor the fact the transmission is probably ok.. next time on the boat I am going to give the engine a compression test. and reflect all winter on what it is.
Bob,
What's your rationale for a compression test?
From your info, the engine turns at near the correct RPM, the shaft turns at near the correct RPM.
There's no RPM issue based on your data.
If the shaft is turning at the correct speed, logic says the issue is behind the transmission -- ie, a prop issue or a hull issue, or are motoring through molasses. :think
kk