Repower questions.....aggghhhh

[Kanani]

Originally Posted by richard_kilburn

I am a sailer more than anything, so the engine really is an auxiliary,

...............however it would be nice to have something that will be able to push into heavy seas and still maintain good forward momentum.

These are contrary statements.

If you have heavy seas, why would you want to motor into them?? Just curious. Sorta sounds like you want a motor-sailor.

I'm not sure why you think motoring a sailboat at 6kts (144 miles per day) is not a good thing. That's sorta normal for that size vessel. Any more than that and you are just pushing fuel and $ out the exhaust pipe.

You may be wise to stay away from turbos. Just something elso to go wrong IMO. 55HP is huge for that boat. You'll brobably be able to push her at 7.5kts (180 miles per day)......but you've gotta ask yourself....why?? . Is 36 miles per day worth that much $ to you?? So, you get to port 1/2 day faster (if you are becalmed somewhere). What will you do with all that extra time??

It's your $ and maybe you have plenty of it. If you do, the Yanmar 55 is a great engine. Myself......I'd keep that 4108. They last forever but they are noisier. If it is having a problem (doesn't sound like it is) get it fixed. Sounds to me like you may do well pulling the injectors out and getting them serviced and have the prop re-pitched so that you can use the HP that the engine has. JMO.

If you are only getting 2100RPM out of that engine (with a clean boat bottom), you are working at about 60% efficiency. No wonder you are frustrated. However, a new engine may not be the best or most efficient solution.

[Joli]

You might also consider a Westerbeke. We have the 108C6 and have been happy with it. We yanked the old one with 6,000 hours and installed the new 108, mated to a Velvet Drive, and turning a Max Prop. Very happy with the setup. No turbo.

Oh, and you can get any alternator you want.

Westerbeke Corporation: Deisel Engines

[richard_kilburn]

Originally Posted by Kanani

These are contrary statements.

If you have heavy seas, why would you want to motor into them?? Just curious. Sorta sounds like you want a motor-sailor.

Let me clarify, there are certain circumstances where you simply have to motor into heavy seas for a short period of time - we had a couple this year in Fiji getting through reef passes where you have little room for maneuvre. In one particular case we were trying to round a reefed headland and the 4108 struggled. Having sails up would have been pointless given we were heading directly into wind. It is extremely rare, but it's nice to know you have a bit up yer sleeve for situations that call for it.

My passage from Fiji to NZ this year saw the 4108 break down due to air in the high pressure pump to injector line due to a crack. This meant 4 days of beating to windward and then sailing to Q-dock in Opua. Another reason the 4108 got the thumbs down. Again, nothing wrong with the core engine, far from it, but the age of the peripherals letting us down at a very bad time. We were lucky in that we had a BFH (1030) to get us to NZ, but in other weather patterns we could have been hammered.

Originally Posted by Kanani

I'm not sure why you think motoring a sailboat at 6kts is not a good thing. That's sorta normal for that size vessel. Any more than that and you are just pushing fuel and $ out the exhaust pipe..

Totally agree - I motor at 5.5kts normally. However sometimes you find yourself in situations when you simply can't maintain 5.5kts as above. They are rare, but do happen occasionally.

Originally Posted by Kanani

You may be wise to stay away from turbos. Just something elso to go wrong IMO. 55HP is huge for that boat. You'll bropably be able to push her at 7.5kts......but you've gotta ask yourself....why?? ..

When installing marine engines, the industry std is to install an engine capable of getting the boat up to hull speed (heavy displacement yachts) at full revs. According to Tayana - that means something from 50-80hp for the Tayana 42. Most people have commented that a Yanmar 55 is on the small side for the yacht! Terminal hull speed is just under 8kts.

Originally Posted by Kanani

It's your $ and maybe you have plenty of it. If you do, the Yanmar 55 is a great engine. Myself......I'd keep that 4108. They last forever. If it is having a problem (doesn't sound like it is) get it fixed. Sounds to me like you may do well pulling the injectors out and getting them serviced and have the prop re-pitched so that you can use the HP that the engine has. JMO.

If I was not planning to live aboard for the next 10 years and cruise remote parts of the planet - I would totally agree. And unfortunately I don't have lots of $$$'s hence why I'm doing the install myself. That way I can learn about the boat, do some re-wiring and re-plumbing while the engine is out, and clean up my oily bilge!

[DeepFrz]

Don't size your prop to small. You want to leave 3 to 5 hundred rpm. less than max. at the top. Check out the online prop. calculator and you may find that the prop. you have will do very well with one of the available transmission ratios.

[never monday]

Originally Posted by DeepFrz

Don't size your prop to small. You want to leave 3 to 5 hundred rpm. less than max. at the top. Check out the online prop. calculator and you may find that the prop. you have will do very well with one of the available transmission ratios.

Gotta disagree

Prop the boat so it will achieve the highest SOG for the maximum RPM of 3000 on the 4JH4E.

The 3000 number is a MAX rating and should not be run at that speed for more than 60 min. Maximum continuous rating is 50hp@2907 RPM, this can be run all day long until the cows come home.
THis leaves you with a one hour reserve built in.

[MikeNZ]

Hi Richard

I had exactly the same problems with my Perkins 4-108 - max revs 2100. My problem was a bit more complicated (see my Rusty Valve Thread) but the main problem was over-propping. The 4-108 is nowhere near its ideal rev range at 2100rpm. I believe your 4-108 is the "New" model like mine. These are rated at 51 Hp at 4,000 rpm. If you examine the HP curve you will see that at 2100rpm you are closer to 40Hp. When you take off the HP absorbed by the alternators, gearbox, shaft bearings, etc you begin to see the problem. In my case I am keeping and rebuilding my 4-108 and re-propping to run between 2400 and 3000 rpm where it will be in a much more efficient portion of the power and torque curves.

I, too, loooked at the Yanmar 55HP option vrey closely. I had the same issues with my boat being set up with best access to the left side of the engine, but most compelling was the total cost of the change - when I added up everything. My total for changing to the Yanmar was very close to $30,000 as opposed to around $10,000 for the rebuild option.

If money was no barrier I would have gone the Yanmar way and lived with less than ideal access, but I have more pressing things to spend the $20,000 on.

BTW is that your 4-108 for sale on TradeMe?

Cheers

Mike

[richard_kilburn]

Hi Deepfrz!

Can you point me in the direction of the online prop calculator? I reckon you're right, but the one I've got at the mo is far too over pitched - given I can't get the engine past 2100 and it should go to 3600......could also be something wrong with the engine, but it seems to run fine.

[richard_kilburn]

Originally Posted by MikeNZ

If money was no barrier I would have gone the Yanmar way and lived with less than ideal access, but I have more pressing things to spend the $20,000 on.

BTW is that your 4-108 for sale on TradeMe?

Cheers

Mike

Yep - it's the one on trade-me that sells on Monday. Had a couple of guys look at it already - it's a great motor cos of the rebuild in 04.

I don't have heaps of cash - but I worked out that the cost difference was closer if you include your time and then the additional stuff I want to do to the boat while the engine is out. Plus at the end of the day, the boat is more saleable with a far newer yanmar than an ancient perkins.
Also - the wife is working at the moment and she's really keen on the engine so who am I to argue! She'll probably end up paying for most of it - I just have to fit the bloody thing!

Big thanks for the calculator offer!

Richard

[Boracay]

In a similar situation to you (though my engine was far worse) I elected to go with a John Deere 4045 mated to a ZF 63 box. 75 genuine clydesdales from 4.5(yes that's 4.5, not 2.2) litres.

Price was $20k as opposed to $16k for the 55 hp Yanmar.

I could not find a mechanic to install the engine but the John Deere rep. (Thanks to Paul Gwyne) worked with me and I did it myself. Took three months.

Installation costs came to around $4k. (Custom welding, engine mounts, hoses etc.)

I am going to get the prop repitched next time I haul.

I have used the following sites to calculate my prop specs. The seem to have some connection to the real world.

I used 46% slip as suggested by Gerr.

Prop diameter calculator. Scroll down to Exalto Holland's nomogram

RBBI Prop Calculator.

BoatRamp.com prop calculator.

ContinuousWave prop calculator.

[Islandmike]

I have a Mariner 40, around 27000 lbs, I repowered with a Westerbeke 64. I turn an 18x15 prop and run it around 2000 to reach hull speed. Max RPM for this engine is 2800. Fuel usage is good, it is quiet and seems to run very well. I only have 60 hrs, so almost too new to assess. But at this point I really like it.

[Alan Wheeler]

Let me clarify, there are certain circumstances where you simply have to motor into heavy seas for a short period of time -

Yeah, it's called sailing in NZ. :-)

Don't size your prop to small. You want to leave 3 to 5 hundred rpm.

Absolutley wrong. You need to be close to full RPM. A max of 10% less is OK. No further.

[richard_kilburn]

Originally Posted by Alan Wheeler

Yeah, it's called sailing in NZ. :-)


Absolutley wrong. You need to be close to full RPM. A max of 10% less is OK. No further.

Hi Alan

I have now spoken to about 5 prop / engine specialists and they all agree that max boat speed should come at max engine revs (for the given engine). I now know that my existing prop is over pitched and that the new one will be designed to hit max speed at max engine revs. I'm guessing one of the previous owners thought it was a good idea to over prop for some reason. The perkins I have has never burnt oil or had any smoke issues out the back since I've owned it and so I'm guessing the current prop hasn't caused any real problems, other than when we are in a strong headwind / seas and we can't maintain speed.

[AnchorageGuy]

Richard, When we considered re powering we had some interesting conversations with the Perkins folks. First they did not want to be forthcoming with information until I threatened to go on the internet and start looking for folks that wanted to enter into a class action suit. The details are too long and complicated but here are the basics. My Mariner was built by Tayana BTW. The entire engine is not really set up to deliver in the marine environment as Perkins had led us all to believe. The exhaust, according to them should be at least 3" but ours was 2" and there is no way to change that on the engine. So according to Perkins there is a 20% loss in HP right there. The ratings are 50HP at 4000 RPMs however they admitted that this figure was on a bench with no load and it would be impossible to achieve this on our boat no matter what we did. The transmission also entered into the equation as to the ratio, in our case 1.91 to 1. Forgetting the prop at this point with our set up we were developing 27HP at the prop and no way to improve on that with the 4-108. Our max RPMs were 2000 and anything over that would overheat the engine and yes we too were over propped. We almost lost the boat in a gale in the Bahamas because of this and spent a lot of painful hours motoring against currents. The Yanmar has been in since 2001 and there is no comparison to the old performance. It has increased many fold. We new we made the right decision when moving from the mechanics dock back to our slip and we got yelled at for our wake. The engine turns at 3400 RPMs under load with our 17X9 three blade prop.

[Charlie]

My boat is 21500lbs displacement. I repowered a 4JHE with a 4JH4E. Difference in power is amazing. I have a maxprop. I guess here is another thing to learn How do you know if you are under or over propped. I cruise comfortably at 2500 rpms 7 knots and haven't turned it up so that to see if I can get to the 8 knot hull speed at 3000rpms.

[Windgeist]

I scanned the post, if it has already been mentioned oh well...but here goes...

What ever motor you choose, check to make sure the footprint is the same or very similar. The cost of having to rebuild motor mounts and surrounding bulkheads, etc will be big bucks and a lot of headaches.

I would first start by looking for engines that will fit easily in the footprint you already have, then choose from those, if you even have choices