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Catalina/Capri 25/250 Sailor's Forums

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C25 with Diesel questions

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jmoritz
Deckhand

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21 Posts

Initially Posted - 07/06/2005 : 12:30:31

I have a 1987 C25 FK/SR with a Universal M-12 diesel engine which I have owned for the past year and a half. At this point I have performed all of the general maintenance on the engine and it seems to be running perfectly. I have good throttle response, no overheating, no oil consumption, no coolant consumption. Trans and prop appear to be original and in good working order. Everything checks out. I believe that the engine is all original with no serious work ever done on it. The question I have is about performance. When I bought the boat the Tachometer would read between 700 and 1900 RPM from idle through full throttle. This seems very low for the top end(should be around 3600 RPM). I checked the throttle setting and it appears to have the original lockwire still in place and presumably has never been adjusted since it left the factory. Next I pulled the tach to check the settings on the back. The book shows a series of dip switches with different settings for different models. The tach on my Catalina gauge package has a three way selector switch A, B or C does anyone know which one is correct? It was on A. Switched to B it indicates between 1000 and 2800 from idle to full throttle. On C it is something like 1500 to 3500 though I cannot recall the exact numbers. So the question is which one is correct or are they all wrong due to some other factor? The next part of the question involves boat speed under power. According to my GPS at full throttle I'm doing 5 knots give or take a little. This seems slow for a 10HP engine at full throttle. Even accounting for the 51 amp alternator I should still be getting 8HP correct? I figure I should be able to get close to 6 knots at full throttle and 5 at reduced power for cruising. Since I do not trust the Tach I do not know exactly how fast the engine is turning. Can those of you with Diesel models comment on what I should expect this engine to do on this boat. I am assuming that the engine, prop and throttle setting were all matched originally to operate together. I appreaciate any input you can provide.

Thanks

John
C25 #5573 FK/SR
Fleet 25

John Moritz
C25 #5573 FK/SR diesel

Edited by - on

JimB517
Past Commodore

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USA
3285 Posts

Response Posted - 07/06/2005 : 15:34:39

is the bottom clean and what is the status of the prop?

The 10 HPO diesel should easily move you at 6.5 knots or higher (slack current, no wind). Badly fouled bottom or prop with growth on it could explain your problem.

Idle speed should be around 600 rpm.

When you go to full throttle is the engine badly loaded up, belching black smoke?

Edited by - on

ClamBeach
Master Marine Consultant

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3072 Posts

Response Posted - 07/06/2005 : 20:37:29

If you're only making 5.5 at full throttle I think that backs up your tach reading of 1900 RPM.

I suspect you're really not making your full hp. When you're talking about seeing 1900 full RPM is that with the boat in or out of gear (or both)?

Edited by - on

ronrryan
Admiral

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USA
561 Posts

Response Posted - 07/06/2005 : 21:27:38

You need to get a tach or a strobe on the shaft to find what the rpm actually is, and correlate that with your gauge.

Edited by - on

Douglas
Master Marine Consultant

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1595 Posts

Response Posted - 07/06/2005 : 23:28:16

I have a 1983 Alberg 29 with a Yanmar 2GM. I had a very similar problem. It turned out that the exaust/mix elbow was carboned up restricting the exaust . I took the exaust apart and my running range is 850 to 3200 rpm . I recomend you have a look at the exaust system .

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Dave Laux
Captain

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318 Posts

Response Posted - 07/07/2005 : 06:58:37

First no load the engine. Push the control to max RPM with the transmission in neutral and the engine running. Tach should read about 200 to 300 RPM above whatever the engine rated RPM is. Set Tach dip switches to read that. Now run in gear and see if you turn to near rated RPM. If not look at engine alignment, exhaust blockage, bottom cleanliness, propellor condition, etc. This engine will idle about 7 to 800. Dave

Edited by - on

jmoritz
Deckhand

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21 Posts

Response Posted - 07/07/2005 : 10:04:44

Thanks for the input so far. Bottom is clean. Prop is clean. Exhaust looks good and is not excessively smoky. Max RPM is about the same in gear or in neutral. In my mind this would eliminate any type of overloading problem. Therefore, if the engine is truly only running up to 1900 RPM it would give credance to an exhaust blockage or possibly a restricted fuel flow? I know I've got good flow to the engine but don't know about the injectors. I'll see if I can get a tach from someone to very the RPMs. I'll also check the exhaust situation. If it was a clogged exhaust wouldn't I see evidence at full throttle of the thing loading up and producing more smoke?

Thanks,

Edited by - on

JimB517
Past Commodore

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USA
3285 Posts

Response Posted - 07/07/2005 : 11:28:20

fuel flow problems will cause the engine to "surge and die" at high rpm. Air restriction problems will cause black smoke, as will overloading due to bad prop or fouled bottom. Fouled injectors or injector pump problems will ofen cause white smoke (unburned fuel).

There is a governor that limits top RPM. This is controlled by a spring. There are a host of injector issues that could be causing the problem. There could be low compression in the cylinder (head, valves). Since you're not burning oil rings are most likely OK. Make sure oil level is not going UP. That is caused by diesel running down into the crankcase, can be caused by a bad injector.

Edited by - on

Dave Laux
Captain

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318 Posts

Response Posted - 07/07/2005 : 18:14:53

Max RPM should not be the same in gear as it is is neutral. If it is your prop is undersize in diameter or pitch. What is your no-load RPM? What is your full load( WOT in gear RPM). Dave

Edited by - on

ClamBeach
Master Marine Consultant

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3072 Posts

Response Posted - 07/07/2005 : 21:36:35

The thought crossed my mind that this problem might be a simple as a mis-adjusted throttle cable?

Check to make sure you're getting the injector pump all the way to the 'stop' when you apply full throttle (should be able to check this with engine stopped)

Edited by - on

Douglas
Master Marine Consultant

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1595 Posts

Response Posted - 07/08/2005 : 00:29:07

I had no signs that my exaust was pluged other than low RPM. Took the mix elbow apart and the hile was down to the size of my small finger from 1 3/4 "

Edited by - on

jmoritz
Deckhand

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21 Posts

Response Posted - 07/08/2005 : 08:37:34

Here's the update. I put a Tach on it and the oroginal RPMs were correct. Idles at 700, max at 1900 RPM. Throttle cable opens all the way to the stop on the engine. When I move the set screw to allow the throttle to open more the engine speeds up (although not as much as I expected). I backed the screw off 4 or 5 turns and got up to 2200 RPM and a boat speed of about 5.2 knots. I have not tried to open up the mixing elbow yet since that will be more involved. The question now is... if it simply needs to have the throttle opened up, why was it set where it was originally? Or am I just compensating for another issue. If douglas is right and I have a blockage, would I be able to get the RPMs up by simply adjusting the throttle or would the bockage be self limiting? To take it apart do I just have to remove the hose where it clamps on or do I have to go farther up to the manifold?

Thanks in advance.

Edited by - on

ClamBeach
Master Marine Consultant

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3072 Posts

Response Posted - 07/08/2005 : 10:01:44

>If douglas is right and I have a blockage, would I be able to get the RPMs up by simply >adjusting the throttle or would the bockage be self limiting?

IMHO: A significant blockage will likely be self-limiting. You'll start getting into an over-fueling state and make lots of black smoke trying to get your full RPM.

I suppose you could do a quick experiment and back the screw out some more... see what happens. Hmmm.... who knows why the stop was set that way and why? Wondering if there may be a high rpm prop or shaft vibration issue the PO was trying to avoid?

BTW, You're not messing with the injector pump governor adjustments are you... just the throttle stop? (injector pump adjustment screws will usually be 'safety wired' or sealed in place).

If you've been running this way for a couple seasons, you might defer tearing things down til fall rolls round. (depends on your circumstances)

Edited by - on

Dave Laux
Captain

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318 Posts

Response Posted - 07/08/2005 : 20:16:08

Observe carefully, does the engine speed up with the movement of the governor arm( throttle lever) and then hold at more or less constant speed at some point as the lever is moved futher. Dave

Edited by - on

jmoritz
Deckhand

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21 Posts

Response Posted - 07/10/2005 : 08:24:25

No, as I move the throttle, RPM's continue to climb until it reached the set screw stop. At no point does it seem to stop havng an effect on RPM at least not yet. I've opened the set screw 4 or 5 tuns to get an aditional 300 RPM. I guess I will open it more and see what happens. I also plan to inspect the mixing elbow when I get the time. There must be a few other c25 diesel owners out there. I'm wonderingwhat they get from the original factory set-up.

Thanks,

Edited by - on

Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 07/10/2005 : 08:54:10

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by jmoritz
 There must be a few other c25 diesel owners out there.
<hr height="1" noshade id="quote"></blockquote id="quote">
I know of one--very knowledgable, but not involved in this forum... I'll try to catch him and get his input.

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Rollo
Deckhand

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USA
4 Posts

Response Posted - 07/11/2005 : 03:15:32

Yes there are diesel owners out here in the background sipping fuel and not worring about outboard issues. If your governor is not cutting in when you change throttle stop settings then go ahead and back it out. The boats run best at 2,700 rpm. Over that r/t hull speed you just waste fuel. Max rpm is approx 3200.

Rollo #5897 SR/WK/IND

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At Ease
Admiral

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672 Posts

Response Posted - 07/11/2005 : 13:54:21

We have lots of smart guys/gals on this forum...however, you might want to try a marine diesel forum: http://forums.torresen.com/sailing/

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