Replace Engine for Sundowner Tug

I have a 1983 Sundowner Tug (30') with a pathfinder diesel 85hp engine. I would like to replace it with a 4-cylinder Yanmar 110hp engine.

Has anyone replaced their engine in a Sundowner and if so, any suggestions.
Thanks.

Hi there, and welcome aboard

The previous owner of our 30' Sundowner Tug, Badger, put in a 100hp Yanmar 4JH2-UTE. It was mounted pretty tight against the forward bulkhead, making the addition of engine driven add-ons (serpentine pulleys or a second alternator, etc) problematic, so I'd advize leaving some wiggle room forward (keeping the boats centre of balance in mind) in case you might want to do that. Also, a bigger engine means less room altogether.

Our most fuel efficient cruising speed is pretty low in rpm...about 2600, or just past where the turbo kicks in. I'm no deisel mechanic (bottom end of the learning curve on that one!) so don't know the long term effects of running the engine that way, but so far it purrs right along as happy as can be. In our first year (about 9 months of boating) we averaged 1.5 gallons per hour.

If I was to repower, I'd consider going back to a smaller engine. While there might be times when all that extra brute power might be handy, dragging the extra weight and burning the extra fuel all the time doesn't seem worth it...then again...I haven't been in a situation where that extra power saved the day either, in which case it would have been worth it after all!

Keep dropping in here...there's lots of good information from others waaaaay more experienced than I, and don't forget to try the advanced search function.

Murray

I think I would opt for the 75 hp Yanmar. It should have plenty of power for a 30' and the lack of an aftercooler is a plus.

David

The base JH engine (55hp) should do fine unless you want more speed. That engine has a great reputation. My fovorite engine is Isuzu and they have a comparable 54hp engine for probably considerably less money. Yanmars are a fairly loud direct injected engine. The upside of that is no glow plugs are needed. I do like my Mitsubishi w pre-combustion chambers and glow plugs.

djmarchand said:

I think I would opt for the 75 hp Yanmar. It should have plenty of power for a 30' and the lack of an aftercooler is a plus.

David

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for engine

Also remember there is a new gear reducer and old prop and drive line (the fore and aft Murray was alluding to) that enters into switch out. This may be a good time to consider a fuel tank replacement if having the engine out gives you access you otherwise may not have.

Second David on avoiding an engine with sea water aftercooler. And get a hydraulic reduction gear. Some Yanmars come with mechanical gears (not sure on the 4JH). Those mech gears are obnoxious.

And while the JH is direct injected, noise is tolerable. A bit easier on fuel too. I like the sound of a DI engine better, even if there is a bit more of it!!

It will fit. the boat next to me is a Sundowner 30 he replaced a VW diesel with a Yanmar JH. It is pretty tight.

SD

I would avoid the high RPM (3600-4000) Yanmar and look seriously at the Beta (Kubota) 60 or 75. These engines put out the rated power at 26-2700 RPM, much closer to the speed you actually use them at. I think it might be (used to be) less money than the Yanmar.

betamarine - Engine View

Tad Roberts said:

I would avoid the high RPM (3600-4000) Yanmar and look seriously at the Beta (Kubota) 60 or 75. These engines put out the rated power at 26-2700 RPM, much closer to the speed you actually use them at. I think it might be (used to be) less money than the Yanmar. betamarine - Engine View

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Yep! I noticed that with our wing engine, it's WAY louder then the main and twice the RPM, also runs very rough.

I've done some looking in the 50 hp range and Beta and We$terbeke would be near the top of my list.
Check out this site:
Repowering Tortuga - Choosing a new Engine

Question,
Why do you want to replace it?
Is it simply to repower because the current engine is giving trouble or you are having trouble obtaining repair parts?
OR
Do you want more speed?
It makes a difference.
Hull speed, so called, is about 6-6.5 knots and your current HP is plenty for that.
If you want to get up to about 8 knots you will be pushing the hull without getting on plane and the hp requirements and fuel will jump a lot.

These boats will plane with enough power but to get it will likely crowd the engine compartment big time.
With 85 hp I'm guessing you have a 4 cyl. Lehman or Perkins.
Be very carefull with measurments. That eng. compartment is tight and you could create a problem if the engine contemplated is much larger than what you have now.

I have a Kubota Beta in my Sundowner. It replaced a Pathfinder.
I'm very pleased.
PM me if you want more info or pictures.

Tad Roberts said:

I would avoid the high RPM (3600-4000) Yanmar

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Excellent advice!

Its amazing how many people will tout a 1800 RPM generator over a 3600 RPM engine, then turn right around and recommend a high RPM unit as the main engine.

I would recommend a engine that developes the HP needed for hull speed operation at a RPM rating that is lower. Actually the lower the better (within reason) with the only real issue being size constraints.

A couple of years ago I looked at various re-powering options and decided the best option at that time was the John Deere 4045D. It developed the full rated HP at 2600 RPM and could matched up with NMEA 2000 gauges giving more options at the helm and for monitoring.

Tom

Tad Roberts said:

I would avoid the high RPM (3600-4000) Yanmar and look seriously at the Beta (Kubota) 60 or 75. These engines put out the rated power at 26-2700 RPM, much closer to the speed you actually use them at. I think it might be (used to be) less money than the Yanmar.

betamarine - Engine View

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Yanmar has been gradually reducing the rated RPM of the JH Series engines. My 4JH3E (2001) is rated at 3,800 RPM and can sound pretty busy at the recommended 85% power - 2,900 RPM.

The latest 4JH5E (N/A Common Rail) engines are rated at 3,000 RPM and the 4JH4-TE (Turbo DI) at 3,200 RPM. At around 2,500 RPM or less they might be more reasonable shipmates. They are also available with either Kanzaki or ZF hydraulic transmissions which are smooth and quiet. They do remain somewhat pricy though.

Good luck in your search.

Larry
m/v Boomarang

Why the need for more horsepower? I'm not aware your boat is suitable for planing speeds. Seems like wasted effort and expense to overpower that boat. Perhaps you have the wrong boat.

tpbrady said:

A couple of years ago I looked at various re-powering options and decided the best option at that time was the John Deere 4045D. It developed the full rated HP at 2600 RPM and could matched up with NMEA 2000 gauges giving more options at the helm and for monitoring.

Tom

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My 2010 JD 4045D is only rated for a maximum 2400 RPM to produce its maximum 80 horsepower. It's happiest at 1800 RPM. (Low RPM engines are gooood.)

In our first year (about 9 months of boating) we averaged 1.5 gallons per hour.

This would AT BEST be perhaps 30HP.

I would look for an engine with NO turbo of about 50 HP.

If the tranny is in good shape you might be able to machine an adapter to continue its use.

If you need to purchase a tranny go 2 sizes larger if you buy a Hirth .

The old Perkins 4-107 or similar would seem ideal , as they dont mind low power operation , lorry engine.

Tad Roberts said:

I would avoid the high RPM (3600-4000) Yanmar and look seriously at the Beta (Kubota) 60 or 75. These engines put out the rated power at 26-2700 RPM, much closer to the speed you actually use them at. I think it might be (used to be) less money than the Yanmar.

betamarine - Engine View

Click to expand...

Like Tad Robert said, I fully agree. The Beta 75 HP. 3.3 litre, I like to add: Paired with at Deep red.ratio i.e. 3:1, from a PRM. hydraulic or a ZF gear, will give a efficient push for the Sundowner 30 TUG.-and low noise, comfortable running, at pleasant 1800/1900 rpm.
_ do not only look at HP.but more for a real TORQ, to swing a big propeller.
Trawler/Tugs want/need that kind of propulsion...!

The US.Beta people (by Stanley), gives good proffesional help.

We're all talking about how much power WE"D put in the Sundowner Tug (ST). And the OP has'nt said anything about how fadt he wants to go. Just that he's thinking about 110hp.

The ST leans on the planing side of SD so he could easily use 110hp or even more. And he will eventually sell the boat. Buyers will expect a reasonable amount of power. Reasonable being what THEY THE BUYER think is reasonable or proper. That's why manufacturers over power SD and even FD boats. I voted for 55hp. Exactly half of what the OP said he was thinking about. One would need to run the ST at 10 knots to use the 110hp engine w/o underloading it. The ST is the wrong boat to power as a FD boat but if the owner wants ... But he will/likely may suffer when he sells it.

So on second thought he should probably go w 100hp or so and chose an engine least likely to suffer from underloading depending on what he thinks about underloading.

But if he wants to limit his speed to FD he should get a FD boat like Mark has already said.

So I think we need to hear from the owner. He has not posted a second post. Find out what he knows about hulls and speed. And the underloading question. And if he cares.

Anode,
How do you usually run your boat? And w how much power?

The OP has received some advice from current Sundowner owners that strongly indicates the install issues are paramount. Key to this decision is not only the engine selection, but the cost estimate from the guys doing the install and other peripheral work. Whether Beta, Yanmar or ??, over half the cost and maybe 90% of the problems will be due to the quality and skills of the outside labor if job is being contracted out.

Being located in MA, you should have several good yards to talk with about fit, ancillary work and schedule. Naturally, the group doing the install should be able to point (proudly) to their previous engine change out experience.

Really cool calculator for determining hull speed and power requirements:

http://www.psychosnail.com/boatspeedcalculator.aspx

The calculator says I need 50hp to achieve hull speed (7.5 knts) in my Gulfstar 36. I have twin 52 hp Perkins 4-154s. If I were to replace them with something more efficient would I be looking at two 25-30 hp engines? Just trying to figure out how to apply this discussion to a twin engine situation.

Hull speed need not be achieved at all. While cruising most all FD boats in our typical size will need 3 to 4hp per ton of displacement for max engine power. 4 to 5hp is more common though. My Willard has 5 and we have a 40hp engine. Only half of that is used to cruise a bit over one knot below hull speed. That gives me a 50% engine load and most engine experts recommend a bit more than that. I don't even know for sure if I can reach our HS of 7 knots. No need to know. I do need to know if my engine will achieve it's rated 3000rpm engine speed. But this all applies only to FD hulled boats. The Sundowner is'nt even close to a FD hull but we can guess that a typical SD trawler hulled boat will require about 1.5 to 1.75 times as much power as a FD boat to perform at about the same speed as the FD boat. That would indicate the Sundowner should need 60 to 75hp to cruise at the displacement speeds of same size FD boats.

However the Sundowner should be capable of going considerably faster with more power unlike our FD boats. The OP is in a position where he can chose to go faster or slower but his decision window will close the moment he buys his engine. Low or high rpm IMO makes no difference.

Some FD boats have only 2hp per ton but they are few and mostly larger craft.

On The Rocks,
Single or twin IMO makes no difference. What is your hp per ton? As a guess I'd be thinking two 40hp engines. I'm not that familiar w your hull either.

On The Rocks said:

Really cool calculator for determining hull speed and power requirements:

Boat Speed Calculator

The calculator says I need 50hp to achieve hull speed (7.5 knts) in my Gulfstar 36. I have twin 52 hp Perkins 4-154s. If I were to replace them with something more efficient would I be looking at two 25-30 hp engines? Just trying to figure out how to apply this discussion to a twin engine situation.

Click to expand...

Most calculators are based upon smooth water. A few large waves will change things quickly as to required HP. Having 2X the calculated HP installed is not a problem IMHO, some of us have 4X and are quite happy about it.

Also to assume smaller engines running at 90% load would be more efficient is not correct, especially when assuming efficiency means total $ spent. Very good engine longevity at low RPMs and 20 to 40 % load is quite cost efficient in terms of maintaining and operating a lightly used boat. Rotating equipment wear goes up exponentially with RPM, about square or 4X for a 2x RPM increase.

Are your engines running OK? A good maintenance program will keep your Perkins 4s running for a very long time. Due to environmental regs they can't make them like your Perkins anymore, I wish they could.

Tom,
Looking at the engine specs tells very quickly what engine speed is most efficient. However I think that's at WOT. I don't think there's much difference underway but running light is definitely not efficient hp per gal of fuel.

And as I've said before I've never ever increased power when in the nasty. And anything I've lost in speed is not noticeable.

And I'm sure no one runs at 90% load on this forum.

But I think your'e right about the OPs Perkins. Only reason I re powered is because we were going to the wilderness.

manyboats said:

And I'm sure no one runs at 90% load on this forum. .

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On The Rocks indeed suggested that as a possibility or question.

Not looking to replace the 4-154s fortunately they run great but parts are hard to find. I was really just trying to get my head around what the most efficient hp to cruise at or near hull speed with twins. I realize I'm never going to go fast in a FD hull so really just need enough to go 7.5 knts with enough reserve to handle heavy wind/current.

Like many have said, much less cost and maint with a power package that does NOT have a turbo and intercooler. Also look carefully where you travel and your own skill at repair, if service and support is critical then need to look at the support network. In this area Yanmar has a very large support network, not sure of the Beta myself.

On The Rocks said:

Not looking to replace the 4-154s fortunately they run great but parts are hard to find. .

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What parts?

Did we scare off the OP?

Paul, I have completed a similar re-power in my 26' Nordic Tug. I downloaded all of the information from all of the diesels that were in consideration (Beta, Hyundai, Isuzu, Iveco, John Deere, Mitsubishi, Nanni, Sole, Universal, Vetus, Volkswagen, Volvo-Penta, Westerbeke, and Yanmar) and made an Excel spreadsheet to compare...

I listed critical boat dimensions:

• Top of engine bed stringers to underside of pilothouse hatch lid
• width of pilothouse door w/ frame removed
• width of pilothouse door
• min height of pilothouse door
• min width of passageway
• min width of companionway doors
• Distance between engine bed stringers
• width of the stringers
• distance from the top of the stringers to hull
• propeller shaft flange to forward bulkhead

I compared ancillary equipage location:

• alternator side
• starter side
• transmission control side
• fuel inlet side
• raw water pump maintenance clearance
• fuel filter clearance
• oil filter clearance

I compared engine dimensions:

• front of engine to gearbox output flange (OA length)
• Front of engine to forward mount
• Front of engine to CL of rear mount
• Engine mount to engine mount
• Rear Engine Mount to Output flange
• OA width
• Mount to mount (CL) width
• OA height
• Crank to top
• Crank to bottom
• Crank to output flange

Now you know what will fit.

Of course price and delivery were compared along with critical spare costs.

I created hp and torque curves and plotted them on the same axis spacing (tricky engine manufactures change plot to make them look flatter) like the graph below.

Now you can play around with prop calculators, specific fuel burns and the like to optimize you cruising speed. Make sure you know your prop clearances.

Have fun!