OK just for comparison. Today winds less than 10 kts no current at 2100 rpm my GPS showed 5.1 kts. at 3150 RPM (MAX) I ran about 6.7 to 6.8. What are you getting?? Fairwinds Skipper Ken
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Why such low rpm's?
If I understand you correctly the tach reads 3150 when the throttle is wide open. It would seem like your best cruising rpm is around 2700 rpm. I own a different model engine than you but our diesels like to run close to full power. I can hear the "happy place" when the engine gets up to about 2800 on my C42. After that point noise level increases and speed gains are marginal because I a approaching hull speed. Bob V
If I understand you correctly the tach reads 3150 when the throttle is wide open. It would seem like your best cruising rpm is around 2700 rpm. I own a different model engine than you but our diesels like to run close to full power. I can hear the "happy place" when the engine gets up to about 2800 on my C42. After that point noise level increases and speed gains are marginal because I a approaching hull speed. Bob V
alternator
It would seem to me that your putting a lot of faith in everyone's tach being accurate. When I had a charging issue I changed the alternator out several times. With each new repalcement alternator the tach read differant RPM's. I don't really know why,.. it just did. Food for thought. Jack
It would seem to me that your putting a lot of faith in everyone's tach being accurate. When I had a charging issue I changed the alternator out several times. With each new repalcement alternator the tach read differant RPM's. I don't really know why,.. it just did. Food for thought. Jack
Tachometers like knotmeters
are nototriously innacurrate. But the best cruising rpm according to the yanmar and westerbeke manuals is a lot closer to full power that 2/3 rds of the way there. If Ken's tach reads 3150 at full power and he cruises at 2100 he can crank it up a lot higher and his engine will be "happier" and he will be closer to hull speed. My Yanmar manual states that maximum throttle is 3000-3200 and cruising speed is 2800 or lower. It also states that the engine should be brought up to max rpm for 5% of the time or 30 minutes out of every 10 hours. This is to prevent cylinder wall glazing by operating continously a low rpms. From this information (provided by Yanmar) I would guesstimate that the best cruising speed for Ken is 2800 rpms. That is considerably higher than the 2100 rpms that he is presently using. When you change out your alternator you should check the tachometer against a timing light for accuracy and recalibrate. Bob V
are nototriously innacurrate. But the best cruising rpm according to the yanmar and westerbeke manuals is a lot closer to full power that 2/3 rds of the way there. If Ken's tach reads 3150 at full power and he cruises at 2100 he can crank it up a lot higher and his engine will be "happier" and he will be closer to hull speed. My Yanmar manual states that maximum throttle is 3000-3200 and cruising speed is 2800 or lower. It also states that the engine should be brought up to max rpm for 5% of the time or 30 minutes out of every 10 hours. This is to prevent cylinder wall glazing by operating continously a low rpms. From this information (provided by Yanmar) I would guesstimate that the best cruising speed for Ken is 2800 rpms. That is considerably higher than the 2100 rpms that he is presently using. When you change out your alternator you should check the tachometer against a timing light for accuracy and recalibrate. Bob V
RPM/Speed comparison
Ken, I can't remember the exact numbers I get, but I think they're pretty close to yours. When I get my boat back out, in March, I'll have to check my speeds to see how they compare. I've been curious about this for the last year, in fact, and just never thought to post the info here. I'm glad you thought of it. Mark Z
Ken, I can't remember the exact numbers I get, but I think they're pretty close to yours. When I get my boat back out, in March, I'll have to check my speeds to see how they compare. I've been curious about this for the last year, in fact, and just never thought to post the info here. I'm glad you thought of it. Mark Z
When I'm running the engine...
for long periods of time, I will usually vary the rpm's periodically. I HAVE run my diesel at full throttle for HOURS and have had no problems whatsoever. I have a Universal M25XPB and, according to my dealer (when we purchased the boat brand new in '05), this engine loves to be run at full throttle (I typically get about 7 knots depending on Lake Erie conditions). My only issue is that, at idle, the engine vibrates like crazy (causing bracket failure etc). I now increase the throttle immediately after starting and everything seems to smooth out...
for long periods of time, I will usually vary the rpm's periodically. I HAVE run my diesel at full throttle for HOURS and have had no problems whatsoever. I have a Universal M25XPB and, according to my dealer (when we purchased the boat brand new in '05), this engine loves to be run at full throttle (I typically get about 7 knots depending on Lake Erie conditions). My only issue is that, at idle, the engine vibrates like crazy (causing bracket failure etc). I now increase the throttle immediately after starting and everything seems to smooth out...
when it runs
I have the same model engine on my C310 and I would add "when the engine is running". I have had nothing but problems with the fuel pump on this engine varying from runaway engine to not pumping at all. The fuel pump is now undergoing it's 3rd rebuild in the last year, and no one seems to know what is gumming it up. I will never-ever buy another boat with a Universal engine after this.
I have the same model engine on my C310 and I would add "when the engine is running". I have had nothing but problems with the fuel pump on this engine varying from runaway engine to not pumping at all. The fuel pump is now undergoing it's 3rd rebuild in the last year, and no one seems to know what is gumming it up. I will never-ever buy another boat with a Universal engine after this.
Speed
GPS speed is speed across the ground, which means nothing in a boat with tides, wind, currents, etc. affecting speed. You need to use speed through the water. I have a Yanmar 3GM30F, with a max RPM of 3600. The manual says to cruise at 80% of max, so I cruise at 2800. However, as noted, the tach is not accurate. Diesels like to work, one guy told my that once a month, pretend the boat is a power boat and run it hard for at least an hour.
GPS speed is speed across the ground, which means nothing in a boat with tides, wind, currents, etc. affecting speed. You need to use speed through the water. I have a Yanmar 3GM30F, with a max RPM of 3600. The manual says to cruise at 80% of max, so I cruise at 2800. However, as noted, the tach is not accurate. Diesels like to work, one guy told my that once a month, pretend the boat is a power boat and run it hard for at least an hour.
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