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Old 03-09-2013, 04:00   #16
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Re: Yanmar Horsepower

Thank you, I will have the engine checked by a qualified mechanic and hope they find something.I actually increased revs only when the revs started to die....
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Old 03-09-2013, 04:23   #17
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Re: Yanmar Horsepower

Quote:
Originally Posted by noelex 77 View Post
Possibly. I think its more likely you increased the engine revs to compensate for the slow SOG and this resulted in a fuel starvation, or overheating as Stevensuf has suggested. There are other possibilities such as a blocked exhaust elbow, or even a plastic bag around the prop.

The main message is the engine problems were not caused by the current. Therefore you should do some investigation to determine what caused the problem.


That would be my guess, too.

If you were looking at SOG instead of speed through the water, it would only be natural to crank up the throttle to try to reach your "normal" speed, at which point something went wrong.

"Something" would be all the usual diesel problem suspects:

1. Fuel
2. Fuel
3. Again fuel
4. Something caught on the prop
5. Overheating
6. Turbo problem
7. Overfilled oil sump; oil thrown up into the intake tract (don't laugh; happened to me once)
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Old 03-09-2013, 04:27   #18
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Re: Yanmar Horsepower

Thanks Guys, appreciate your input.............off to the local diesel mechanic!!
good sailing.
Incidentally.................sailing the Whitsunday islands was fantastic!
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Old 03-09-2013, 05:11   #19
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Re: Yanmar Horsepower

Dockhead,
I had a strange overfilled oil sump once, which managed to keep on re-filling itself, from the fuel pump diaphragm with nice fresh tank diesel, boy was it a bugger to stop the engine that day!

I think the original poster said the prop was free, so does sounds like fuel/heat issues!

I remember having the boat point to 70 degrees to make a course of 0 degrees, heading 70 degrees at 7 kn to make 2kn to the north. (not fun)
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Old 03-09-2013, 05:26   #20
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Re: Yanmar Horsepower

Dont try sailing around the Cherbourg peninsular or through the Pentland Firth where tides can be expected to be at least 7 kts, and in certain areas can reach 11 kts.

SOG is usefull, but so is the Speed through the water - something that my Raymarine system is very reluctant to provide at the moment. I have renewed paddlewheel and through hull module. I guess the next is the DSM module or the E80 itself.
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Old 03-09-2013, 05:29   #21
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Re: Yanmar Horsepower

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Originally Posted by stevensuf View Post
I remember having the boat point to 70 degrees to make a course of 0 degrees, heading 70 degrees at 7 kn to make 2kn to the north. (not fun)

BTDT!

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Old 03-09-2013, 05:30   #22
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Re: Yanmar Horsepower

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Dont try sailing around the Cherbourg peninsular or through the Pentland Firth where tides can be expected to be at least 7 kts, and in certain areas can reach 11 kts.
I'm off to Cherbourg next week.

My usual cruising grounds.
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Old 03-09-2013, 09:30   #23
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Re: Yanmar Horsepower

Lastly, the author's OP likely includes a miscalculation. It states a displacement of 19 tons. This is ridicuous.
It appears from literature that a Irwin 38 MkII is on the order of 20,000 pounds, with other models in the 15,000-16,000 pound range.
Assuming the OP meant to state 19,000 pounds, this tranlates to 9.5 short tons or 8.5 long tons...a far cry from 19 tons.

The subsequent post sugesting rough estimating technique of 3-4 HP per ton, would then give a engine with 36 HP as a starting point at the high end. Which as we know, is reasonable for a boat of this size.
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Old 03-09-2013, 10:20   #24
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Re: Yanmar Horsepower

Quote:
Originally Posted by Dockhead View Post
I'm off to Cherbourg next week.

My usual cruising grounds.
I spent a couple of happy weeks in that area this summer as well. Simple stuff if you bother to work out the tides.
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Old 03-09-2013, 10:36   #25
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Re: Yanmar Horsepower

In theory current wont effect it. In reality it does! I'm not sure why... maybe it's the turbulance in the water degrading the prop performance? Been there done that many times in the strong currents up here in the PNW. Swirly, twirly whirly water, effecting the rudder also... boat slows down. Probably side currrents too. Is running on a tread mill harder if the belt is going diagonal instead of the direction your running?
OP: what rpm do you normally run? Yanmars are rated up at high rpm... if you're not running up there you may be only 30 hp or less.
What RPM does your prop limit the engine to?
Your boat displacement estimate seems real high for a 38...? 38000lbs for an Irwin?
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Old 03-09-2013, 11:03   #26
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Re: Yanmar Horsepower

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Originally Posted by Cheechako View Post
In theory current wont effect it. In reality it does! I'm not sure why... maybe it's the turbulance in the water degrading the prop performance? Been there done that many times in the strong currents up here in the PNW. Swirly, twirly whirly water, effecting the rudder also... boat slows down. Probably side currrents too. Is running on a tread mill harder if the belt is going diagonal instead of the direction your running?
OP: what rpm do you normally run? Yanmars are rated up at high rpm... if you're not running up there you may be only 30 hp or less.
What RPM does your prop limit the engine to?
Your boat displacement estimate seems real high for a 38...? 38000lbs for an Irwin?
Turbulent water and a current are two different things, even if they sometimes go together.
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Old 03-09-2013, 11:03   #27
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Re: Yanmar Horsepower

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Originally Posted by Talbot View Post
I spent a couple of happy weeks in that area this summer as well. Simple stuff if you bother to work out the tides.
Not bothering to work out the tides is not an option there

Unless you want to pay an unplanned visit to Alderney
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Old 03-09-2013, 12:05   #28
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Re: Yanmar Horsepower

A power loss at near max rpm could also be a partly clogged discharge elbow, where the back pressure increases till the engine is laboring. At lower speeds it would be fine.
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Old 04-09-2013, 02:27   #29
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Re: Yanmar Horsepower

Ok, so if we're guessing why the engine lost revs I'll put my money (but only a few shekels) on an over pitched prop.

Most of the time it would make no difference but if full power were applied to an over pitched prop then the engine may overheat and some power would be lost.
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Old 04-09-2013, 04:39   #30
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Re: Yanmar Horsepower

OK, a few clarifications seem due...
yes displacement is 20,000lbs according to survey,apologies if this was misleading.
Yanmar is model 4JHE 44hp
prop is Martec Autostream feathering 3 blade.
revs when motoring generally 3000rpm which is less than max revs( I never use max revs)
Discharge elbow was replaced six months ago
Overheating has been experienced previously when impeller was broken, this triggered alarm. No such alarm in this situation.
Not sure what rpm limit from prop.....where can I find that info?
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