• Mobile App For Android Now Online!

    Download it here. The app is searchable in the Google Play Store under Sailboat Owners.

    Sorry iPhone/iPad users, we are still waiting on Apple. :(

    Click the X in the upper right corner to make this go away

Engine power issue

Jun 2, 2014
356
Catalina 30 mkII - 1987 Long Beach Shoreline Marina
87 mkII with M25XP
I just spent a few days in Catalina. Motor sailing the entire time.
the way there everything was normal, cruising at 2200RPM, no issues.
after anchoring and then leaving to fish, I couldn’t get the motor over 2000RPM at all. Last time that ever happened I got kelp wrapped on the prop and was able to clear it in reverse. This time it didn’t change and I even dove under to check and everything looked clean around the shaft and prop. I have a two blade folding prop. At some point later it seemed normal again and we motored on.
Then the next day, it was again limited to 2000RPM under power.
In neutral, it idles at 800 and I can WOT up to 2900 RPM.
we motored home 6 hours at 2000RPM, no overheating issues, and we were going the normal 5.9-6.1knts I usually get, but I feel like the fuel efficiency was also poor. I used about 10 gallons for about 12 hours total of motoring.
I normally can run the RpM’s well above 2000RPM even under power.
I just tested it at the dock tied up and got the same thing, maybe even less like 1900 RPM max.
Looking for suggestions and any advice.
I read some comments from others about running injector cleaner through it.
Any other thoughts?
Thank you.
 
Jun 2, 2014
356
Catalina 30 mkII - 1987 Long Beach Shoreline Marina
I haven’t a clue how to check or deal with the exhaust riser. I can certainly do my yearly filter/oil maintenance early and add injector cleaner to the filter bowl as I’ve read.
is there anything simple to check on the exhaust riser?
 
Jun 2, 2014
356
Catalina 30 mkII - 1987 Long Beach Shoreline Marina
Besides removal and repair or replace? No, I don't think so.
How do you check it to know if it’s bad if you don’t know what bad looks like?
I’ve just never taken one apart. How likely is it bad?
 
Feb 20, 2011
7,372
Island Packet 35 Tucson, AZ/San Carlos, MX
How do you check it to know if it’s bad if you don’t know what bad looks like?
I’ve just never taken one apart. How likely is it bad?
Perhaps someone else has some experience with your particular model.
"Bad" will have you asking yourself "How did ANY exhaust get through that crap???"
As for having never taken one apart, well, that's what men do. Page 42 in the Manly Manual: we take things apart!
I'll admit I'm not looking forward to pulling my mixing elbow off this coming year.
Got a service manual?
Checked Youtube for a primer on your specific engine?
 
Jan 19, 2010
489
Catalina 34 Casco Bay
Diesel engines are actually very simple in their operating needs... Fuel...Air....Heat ( compression). Fuel speaks for itself. It is not only the fuel but the delivery system ( injectors & pump). Air: on the surface it speaks for itself. Let's look a bit deeper. Air can be limited by the filter. It can be augmented by use of a blower. At higher RPMs more air is needed. Many boats have a blower. In gas engines the blower forces vapors out of the engine spaces. With diesel, air is introduced to assist in combustion. Air, continues as exhaust. Beverly Hills Cop... Foley puts the potato into the tail pipe... So too with diesels.. If you can't get rid of exhaust or if there is blockage you will suffer performance loss and even failure to run. Since your engine runs, we can assume that compression ( heat ) is intact. But, worn rings and poor valve seats can play a part in this play as well.
One method of checking the riser is to remove the raw water hose where it is introduced with exhaust gases. Some shops will use a " scope" to view for blockage.

Since you can make 2900 RPM w/o load and only 2K under load with a clear prop, this might suggest the air side...

Good Luck
 

dmax

.
Jul 29, 2018
174
O'Day 35 Buzzards Bay
Also, 10 gallons in 12 hours motoring is more fuel consumption than usual - I use about 1/2 gallon an hour with the same engine. Are you seeing black smoke out of the exhaust at all?
 
Jun 2, 2014
356
Catalina 30 mkII - 1987 Long Beach Shoreline Marina
Also, 10 gallons in 12 hours motoring is more fuel consumption than usual - I use about 1/2 gallon an hour with the same engine. Are you seeing black smoke out of the exhaust at all?
No, but the fuel consumption reminds me of when I have been impatient in the past and run the motor at higher rpm to hurry up.
I used to be impressed how lower rpms dramatically increased efficiency. Now it seems I’ve just got bad fuel efficiency all around.

I think I am going to do all my normal maintenance right now, add injector cleaner, check the air filter, and see what that gets me. If nothing changes, I’ll move on to the elbow. After that I’ll call for help I guess.
 

Tom J

.
Sep 30, 2008
1,630
Catalina 310 Quincy, MA
You don't mention how many hours are on your engine, but given the age of the boat, we can assume it has a lot of hours on it. If the elbow hasn't already been inspected and cleaned, and if the engine is occasionally run at idle, say to charge the batteries, then a blocked elbow is very likely. In any case, pulling the elbow and cleaning it should be on your list of preventive maintenance projects.
 
May 20, 2016
2,927
Catalina 36 MK1 94 Everett, WA
How do you check it to know if it’s bad if you don’t know what bad looks like?
I’ve just never taken one apart. How likely is it bad?
Three bolts and a hose clamp. Be sure and have a replacement gasket, and if your hump hose (from just below water injection point an muffler) isn’t silicone get one. I don’t know how access is on your 310 but getting access is probably the hardest part.

That said, Universals don’t coke up exhaust elbows like Yanmars do. I’m guessing 50/50 that’s your problem.

Your getting plenty of fuel, the bottom is clean, prop is clean, other common causes.

Have you removed the air filter and seen if it makes a difference. Any other changes to the boat?
 
Jun 2, 2014
356
Catalina 30 mkII - 1987 Long Beach Shoreline Marina
Thanks for the advice. Nothing has changed since I last used the boat. I will also mention that it did seem very hard to start this last trip. Had to pre heat the glow plugs much more than normal and it was still hard to start. That was unusual.
I have not checked the air filter yet.
I think I’m going to just do my spring maintenance in the next couple of weeks and check all the things mentioned and see what I find or what happens after.
 
Jul 23, 2009
341
Beneteau 31 Oceanis Grand Lake, Oklahoma
Originally I was thinking that your tachometer might be inaccurate or the belt might be slipping (with an alternator driven tach). The hard starting and the high fuel consumption points to and injector issue. I would expect some smoke though.

Something I would check is the lift pump. It's easy to test and it will cause starting and performance issues if it has failed.
 
Jun 2, 2014
356
Catalina 30 mkII - 1987 Long Beach Shoreline Marina
When you say “lift pump”, are you meaning the raw water pump or the exhaust riser?
I have good raw water flow, and didn’t notice any abnormal smoke.
 
May 20, 2016
2,927
Catalina 36 MK1 94 Everett, WA
When you say “lift pump”, are you meaning the raw water pump or the exhaust riser?
I have good raw water flow, and didn’t notice any abnormal smoke.
The lift pump is the diesel pump that is before the high pressure pump. Some it is on engine mechanical, but most it is electrical and can be on or off the engine depending on the make and model of the engine. M35’s it’s electric on the engine M25’s it’s off.
 
Jul 23, 2009
341
Beneteau 31 Oceanis Grand Lake, Oklahoma
Lift pump = low pressure diesel pump.
Probably not your issue but it could be and its easy to test.
 
Oct 26, 2010
1,065
Hunter 40.5 Beaufort, SC
Probably not the immediate cause of what you note as a loss of power but possibly a contributing cause over the long run. You'll still have to fix the immediate problem but its not a bad idea to see if there are things that may be added to your operating routine, especially if its carbon buildup. Short version is that diesels don't like to be run lightly loaded.

You mentioned you cruise at 2200 rpm. Is that your normal cruising rpm and what is the manufacturer's rated max rpm? My experience (with large commercial diesels) and what I've read indicate that the ideal (and most efficient) cruising rpm is about 75% of rated rpm. For my Yanmar with a max rpm of 3600 that is a cruising rpm of 2700 rpm. I also believe it is wise to run the diesel at WOT for about 5 minutes or so at the end of a cruising day a few minutes away from my destination,, allow the engine to come back to cruise rpm, then allow it to idle and cool down before shutting down. That is my normal routine.. Your milage may vary ;)

Just a thought and something to add to your regular running routine. Of course I'd be happy to hear counters to this routine and other's thoughts. Not trying to hijack the thread but rather to add some perspectives on how to keep it from happening. Running a diesel at too low an rpm encourages carbon buildup. At plants with large emergency power diesels we never ever ran them al low load, but rather loaded them up.
 
Last edited:
  • Like
Likes: Alan Gomes
Jul 23, 2009
341
Beneteau 31 Oceanis Grand Lake, Oklahoma
Smokey, we try to keep our diesel generators loaded to a minimum of 30% to keep the carbon buildup to a minimum.
 
Oct 26, 2010
1,065
Hunter 40.5 Beaufort, SC
Smokey, we try to keep our diesel generators loaded to a minimum of 30% to keep the carbon buildup to a minimum.
30% would be considered lightly loaded for a diesel. I once bought a used Ford 3000 diesel tractor that had "only been used by a little old lady to and from church." (Actually used to mow hay fields, probably at 30% or less of full load). When I got it, it started and idled fine but when I got it on the road, in road gear, to drive it the 20 miles to my farm, it blew out black smoke and bogged down. It just would not carry a load. It took me several weeks of slowly increasing load to get to the point to where it would pull a 2 bottom plow (a pretty good load but not nearly near full load) without bogging down. Finally got it to carry nearly a full load, but it took a long, long time and patience. My practice of 75% full load for normal cruising is based on what I have read about keeping diesels healthy. Again, your boat, your choice.
 
Oct 29, 2012
260
Catalina 30 TRBS MkII Milwaukee
Probably not the immediate cause of what you note as a loss of power but possibly a contributing cause over the long run. You'll still have to fix the immediate problem but its not a bad idea to see if there are things that may be added to your operating routine, especially if its carbon buildup. Short version is that diesels don't like to be run lightly loaded.

You mentioned you cruise at 2200 rpm. Is that your normal cruising rpm and what is the manufacturer's rated max rpm? My experience (with large commercial diesels) and what I've read indicate that the ideal (and most efficient) cruising rpm is about 75% of rated rpm. For my Yanmar with a max rpm of 3600 that is a cruising rpm of 2700 rpm. I also believe it is wise to run the diesel at WOT for about 5 minutes or so at the end of a cruising day a few minutes away from my destination,, allow the engine to come back to cruise rpm, then allow it to idle and cool down before shutting down. That is my normal routine.. Your milage may vary ;)

Just a thought and something to add to your regular running routine. Of course I'd be happy to hear counters to this routine and other's thoughts. Not trying to hijack the thread but rather to add some perspectives on how to keep it from happening. Running a diesel at too low an rpm encourages carbon buildup. At plants with large emergency power diesels we never ever ran them al low load, but rather loaded them up.

Every piece of construction or farm equipment we have is run balls to the wall, worked hard and usually put away wet.
We religiously change oil/ fluids and filters, never have had problems. Was once told that is why they put governors on diesels.