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Author Topic: WOT too low. Speed down significantly  (Read 659 times)

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Oldlaxer1

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WOT too low. Speed down significantly
« on: August 09, 2020, 04:35:00 AM »

My new to me 1987 C34 is struggling to get above 2300 RPM underway.  It was hauled and bottom cleaned on June 24th for survey.  On delivery home I had some steam coming from the exhaust and it was running a bit hot at higher rpms so we throttled back. New impeller solved that problem. We致e only had it out twice for short motoring trips since getting her home due to lousy weather. Took it out yesterday to knock some crud off the bottom and we were very slow across the bottom (GPS speed). I ran it up to full throttle and it only got to 2300 RPM and just over 4kts. I throttled back, shifted to neutral and ran up the throttle and it was well north of 2500 rpm and climbing so I throttled back thinking the issue isn稚 with the tach (even though it had acted up on the delivery home. Cleaning some terminals seems to have solved that issue).  Water temperatures are abnormally high so growth on the prop is possible. I値l check it with a GoPro today. Could anything else be contributing to the low RPM and speed?  I値l check the packing nut temp today while running it in the slip.
Thanks
John
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John Novotny
1987 C34 #298

Jim Hardesty

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Re: WOT too low. Speed down significantly
« Reply #1 on: August 09, 2020, 04:56:27 AM »

John,
My first thought is dirty fuel filters.  That's the symptoms I get when the filters need changing.  Engine runs fine but won't do full RPMs.  And a recently changed filter can be dirty.  Lots of information here on changing fuel filters and the filter of owners choice 2, 5 micron or even more course.  Easy job if all goes right.  I've even changed them underway.

Hope this helps,
Jim
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Jim Hardesty
2001 MKII hull #1570 M35BC  "Shamrock"
sailing Lake Erie
from Commodore Perry Yacht Club
Erie, PA

Oldlaxer1

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Re: WOT too low. Speed down significantly
« Reply #2 on: August 09, 2020, 06:06:34 AM »

Thanks Jim. I値l check them out and replace. I have no idea when they were last replaced so this will get me on a regular schedule. 
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John Novotny
1987 C34 #298

scgunner

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Re: WOT too low. Speed down significantly
« Reply #3 on: August 09, 2020, 07:49:41 AM »

John,

You took it out to knock some crud off the bottom, don't you have a bottom guy? Jim's got the right idea with the filters, but I think I'd just go ahead and do a 100hr service which would set up a good performance baseline and then you can start looking for problems related to individual issues, like low RPM, overheating, etc.. Also when the impeller was replaced were all vanes in place or accounted for?
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Kevin Quistberg                                                 Top Gun 1987 Mk 1 Hull #273

Oldlaxer1

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Re: WOT too low. Speed down significantly
« Reply #4 on: August 09, 2020, 08:16:21 AM »

Kevin, I do have a bottom guy but with my old boat twice a season was plenty. With a full pressure wash on the 24th of June I really wasn稚 expecting that much of a problem, but new boat to me so who knows.   We値l see what the GoPro shows shortly.  I did find all the vanes when changing impeller.  It is running at about 165 after almost an hour of motoring so I知 feeling good about that issue. Oil and filters were replaced just before I bought the boat.  I値l do a search for what else is on the 100 hr.
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John Novotny
1987 C34 #298

Ron Hill

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Re: WOT too low. Speed down significantly
« Reply #5 on: August 09, 2020, 02:27:52 PM »

John : If the new filters don't help increase the engine, look at the RACOR " Obscure check valve" as Stu posted above!!

Also there was a screen on the end of the fuel pickup tube in the fuel tank. I wrote about this over 25 years ago, but you might check it?
That screen can clog, and was eliminated in the 1993? C34 production.

If the boat has been sitting for the past 6 weeks you might check the prop for growth!!

A thought
« Last Edit: September 05, 2020, 01:34:37 PM by Ron Hill »
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Ron, Apache #788

Robert Mann

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Re: WOT too low. Speed down significantly
« Reply #6 on: August 09, 2020, 03:15:27 PM »

John, I am not familiar with the fuel system layout of the Mk-I, but my Mk-II will run quite nicely without the electric fuel pump operating.  However, it will not get close to full engine speed.  The wire to my fuel pump broke and it took me a couple of weeks to find the problem.  Check the fuel pump is ticking.
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Catalina 34 MkII, Indigostar, 2002 no 1622

Ron Hill

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Re: WOT too low. Speed down significantly
« Reply #7 on: August 09, 2020, 04:36:38 PM »

John : That has been posted a number of times - as the fuel tank is higher than the engine (syphoning!!)

a thought
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Jon W

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Re: WOT too low. Speed down significantly
« Reply #8 on: August 09, 2020, 05:10:27 PM »

In addition to the Racor, and on engine fuel filters, the original 87 fuel system tank pickup tube had a hose with a strainer on the end that can clog up. Unfortunately it痴 all inside the fuel tank. Before tackling that nightmare, is the Racor filter bowl full of fuel? If it is, the strainer inside the tank may not be the problem right now. Checking for and removing the strainer, is something you should plan for.
« Last Edit: August 09, 2020, 05:16:22 PM by Jon W »
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Jon W.
s/v Della Jean
Hull #493, 1987 MK 1, M25XP, Std Rig
San Diego, Ca

Dave DeAre

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Re: WOT too low. Speed down significantly
« Reply #9 on: August 10, 2020, 06:21:45 AM »

My 2002 MK 2 also would not run over 2,000 rpm. Replaced the electric lift pump and has been fine for 5 years. Check the pump.
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Overdue
2002 34, roller main, tall rig
Burnham Harbor, Chicago

Oldlaxer1

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Re: WOT too low. Speed down significantly
« Reply #10 on: August 10, 2020, 10:55:03 AM »

My 2002 MK 2 also would not run over 2,000 rpm. Replaced the electric lift pump and has been fine for 5 years. Check the pump.
I purchased a spare pump shortly after buying the boat. I'm kinda anal about spare parts.   I'll be checking the existing pump tonight.  Perhaps it isn't even working and I'm just getting gravity feed per Ron. 
BTW, my Racor is a 500FG Turbine series so Stu's clean out doesn't seem to apply to my situation unless the ball valve is somewhere else.  I'll be looking into that tonight too. 
New filters are on their way.  Hopefully I'll have good news to report. Thanks for all the insight. 
John
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John Novotny
1987 C34 #298

Stu Jackson

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Re: WOT too low. Speed down significantly
« Reply #11 on: August 10, 2020, 12:33:15 PM »

>>>>>>>>>>>>>>>
BTW, my Racor is a 500FG Turbine series so Stu's clean out doesn't seem to apply to my situation unless the ball valve is somewhere else.  >>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>

John is right.  I just Googled Racor 500FG Turbine and the Parker manual says a separate check valve should be installed if the fuel tank is below the filter/housing.

Just like I "discovered" this little gem:  RTFM.   :D :D :D
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Stu Jackson, C34 IA Secretary, #224 1986, "Aquavite"  Cowichan Bay, BC  Maple Bay Marina  SR/FK, M25, Rocna 10 (22#) (NZ model)

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rmjohns

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Re: WOT too low. Speed down significantly
« Reply #12 on: August 10, 2020, 01:58:10 PM »

I had a similar problem in a prior boat that was Yanmar powered. It turned out the exhaust mixing elbow had rusted almost completely shut. It would also get steam since there were tiny holes in the elbow.  I haven't dug into the Universal enough to know if it's laid out the same way, but might be worth looking at.
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Rob

1998 Catalina 34 Mkii 1390 - Ragtop

Oldlaxer1

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Re: WOT too low. Speed down significantly
« Reply #13 on: August 10, 2020, 02:12:43 PM »

I'm definitely hoping it is a filter or pump issue....That exhaust manifold is almost $1,400.00.   
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John Novotny
1987 C34 #298

Ron Hill

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Re: WOT too low. Speed down significantly
« Reply #14 on: August 10, 2020, 02:19:02 PM »

John : Your exhaust riser mixing tube is stainless steel - not like the Yanmar that can rust.

A thought
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Ron, Apache #788
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