Under powered 30'er when motoring

[StuM]

Originally Posted by Searles

Vetus are engine marinisers that engine is not designed to be turbo charged ,do able but verry expensive ,may not be reliable after conversion ,use the top end of the power range .⛵️⚓️

A lot of Vetus engines are marinized Mitsubishi tractor engines.

[pete c]

One thing I forgot to mention.


The OP notes that 11 HP isn't cutting it.

I wonder how much of those precious few HP are eaten by the saildrive?

I really don't get the current popularity of going to a drive system incorporates 2 90 degree power transfers, which I believe is the case, unless there is a belt/chain drive inside it.

Each one of those 90 degree transfers has better than a 10% loss, if what I have read on this topic is correct.

[Adelie]

Originally Posted by pete c

One thing I forgot to mention.


The OP notes that 11 HP isn't cutting it.

I wonder how much of those precious few HP are eaten by the saildrive?

I really don't get the current popularity of going to a drive system incorporates 2 90 degree power transfers, which I believe is the case, unless there is a belt/chain drive inside it.

Each one of those 90 degree transfers has better than a 10% loss, if what I have read on this topic is correct.

Nah, it’s more like 1-3% each, plus 1% for each bearing.

[EWOL Props]

Hi Sheepstations, clearly you have a problem of prop model, it's a 2 bladed folding one, unfortunately that is the worst possible for maneuverability and pull backwards.
These props tend to close into folding position as a reaction when the push the water forward.

See here https://ewol-propellers.com/portfoli...eller-problem/

If you install a feathering propeller you will solve the problem.

Originally Posted by sheepstations

Hi all, have just a bought a 30' yacht which weighs in at 3.5 tonnes. We have had the it out a few times and am a little bit concerned at the lack of power when underway using the engine. From what I can gather, we have either a Volvo Penta MD7A (13hp) or MD7B (17hp) coupled with a 120S saildrive. (I think it might be a MD7A - is there a definitive way to tell?).

When in reverse, if it's blowing over 5knots, I can not make any way against the wind. It feels like the boat's in neutral even when giving it about 1500rpm. Basically I'm feeling very under-powered unless it's dead calm when maneuvering.

So my question is the motor setup fundamentally under-powered for the boat or could it be possibly a propeller issue? With the correct prop, would the engine have enough grunt to enable me to maneuver 'normally'?
BTW, the hull is squeaky clean as I had it of the water last month for anti-fouling.

Any thoughts or suggestions would be much appreciated.
JR

[PineyWoodsPete]

Originally Posted by pete c

Interesting to find this thread right at the top of the heap as I came in here to ask about a Catalina 30 with a Vetus 11 hp.


11 HP does seem to be a little light for a 30 footer, but, lets not forget, these are SAILboats, not motorboats. And I will be a coastal fairweather sailer.

Also, diesel engines are at their best when they are working. I own a VW TDI and that thing just loves to pull hard up hills. I would think a marine diesel would be no different.

Does anyone have anything to say about the Vetus? I had never even heard of them prior to finding this boat.

Looks like it is Mitsubishi based, which ought to be a good thing as Mitsu has made bazillions of diesels.

Also, seems like most diesels in this power range are single pot thumpers. This is a twin, which should mean a very smooth running engine.

One last question. Is it economically feasible to turbocharge this thing?

Turbos are a win/win for diesels. They improve efficiency and power. Pretty much any diesel car made today is a turbodiesel.

We had an '83 Cat. 30 w/ the Universal 5411 2-cyl 11 HP diesel, sailing out of Monterey Bay's Moss Landing marina. The wide-open Bay can be a challenge with the 15-20 NW summer winds generated by Central Valley heating - sort of like SF Bay, with a 5-10' afternoon breaking swell thrown in! Standing waves with ebb tide against the wind in the marina's jettied entrance, etc. At any rate, the little diesel never let us down, but 5.5-6kts top in flat water, and only 2-3 OTG against an ebb tide.

Retrofit a turbo to it? No way - unless you want to re-engineer the whole engine from shaft main bearings to top-end to take the stresses..

[sinnerman]

Do you have a single combined throttle/shifter control, or separate controls for the throttle and and transmission? If combined, make sure it is rigged correctly. In full reverse look at the engine and make sure the throttle is getting a full stroke .

Could your transmission be slipping in revers?

cheers?

[Tetepare]

I'll blame the prop. Get a feathering prop if you have lots of cash, or a fixed prop. A three blade prop will give you more thrust.

[Brioche]

If your engine can turn the prop at desired RPM, it is not exhibiting any lack of power. Either clutch is slipping or prop is not conveying power through water, so boat is not moving as it should. If your clutch is solid, and you solve any prop problems, then you will know if engine is sized properly. An undersized engine will be unable to reach desired RPM with good connection through proper size and pitch prop.

[Boatwright]

We have a VP MD11c which is the 18 hp version with Saildrive in our Niagara 35, and we have no problem backing. In fact because the prop shaft is parallel to the waterline and the prop thrust is directed at the leading edge of our spade rudder (like yours), it is the best backing boat I have ever steered. This hp is more than enough to drive our boat at hull speed. We cruise under power @ 1600 RPM, 5.5 K. 11 hp seems small, but remember these are low rpm diesel ponies with plenty of torque to get the prop and the boat moving as it should.

Your problem is the poorly designed folding prop that was standard eqpt. with many Saildrives. We have a two bladed fixed prop, and unless you are a serious racer after every 1/10 knot of speed you should get one as well.
Props are available to fit the Saildrive shaft splines. You will also need the streamlined hub/nut with a special washer and a special bolt to lock the setup.

Replacing the prop with a fixed two blade will absolutely solve your problem. I suggest you contact other owners of your model to get the recommended dia. and pitch for your boat.

BTW: There has been a lot of discussion about whether one should allow a fixed prop to freewheel with the gear in neutral while sailing. Don't as it causes unnecessary wear. We sail with the gear in reverse.

[hhmcsv]

I have a Swedish sailboat, Beason 31 from 1984 with a MD7B (18hp) and a 120S saildrive. The displacement is 4.3 tonnes.
The folding prop I have looks very similar to yours.
I don not have any issues of lacking power, whether in forward or in reverse. Today, one would probably install 25-30 hp for such a boat, but at the time the 18 hp was plenty - and I still find it plenty. Could it be that the diesel is a bit tired after nearly 40 years of service?

[drdoyle]

The prop is the problem. Put on a fixed pitch 3 blade prop of the largest diameter allowed to match the engine and Transmission reduction ratio. It may cause a little drag while sailing, but it will help prevent crashes.

[GrowleyMonster]

Prop. Try a different one. Maybe temporarily try a fixed two blade. They used to be all over fleabay, probably still are. Just match the diameter and make sure pitch is between 2/3 and 100% of diameter and you are not necessarily optimized, (typically about 75% of diameter is optimal for sailboats or other small displacement hulls) but it should tell you whether the problem is your prop or not. You should be able to change props in the water if you are careful. Try anchoring over sandy bottom with the keel just not quite touching. You can scrape/scrub the hull at the same time and save some bucks by doing it yourself. A borrowed hookah rig and a weight belt (don't improvise, for obvious reasons this should be a quick release rig) with just a couple pounds of lead on it will make the job super easy. You NEED a helper on deck. Rig a milk crate for a lifting basket. It is easier than tying and untying each part or tool.Make sure you have spare shaft keys in pocket, and cotter pins, if used. Spare nuts are nice, too.

Sometimes folding props get fouled and don't fold or unfold properly. My old Cal came to me with an inch thick buildup of sealife. It was a whole ecosystem, complete with some really big barnies. I scraped the blades but there was still gook in the works and it took another dive to get it completely free. Mine backed okay but nothing to write home about, a Cal 2-27 and an Atomic 4. I switched to 3 blade fixed when I repowered electric.

[caffel]

I was the first mate on a heavier 35' cutter with an earlier version of this Volvo for five years. The very first thing we changed after our first sea trials was to a much bigger prop (3 blades and way bigger than your photo).
We were happy with the results for the rest of the semi-circumnavigation.

[Shaneesprit]

Originally Posted by sheepstations

Thanks for the input. Much appreciated.
We had a little 'incident' yesterday where things happened rather quickly but I do recall the boat was facing directly stern to into the wind (around 12 knots) and I did give it full revs to try and get some way up in reverse. I can't quite recall how long I had it at about 2200rpm but guessing about 15 seconds. The boat did not respond in reverse at all and was pushed forward by the wind.
It was this incident that lead me to post something to try and get some perspectives on what happened.

You seem very concerned with the Engine RPMs ?
Diesel engines especially non Automotive engines are designed to run flat out for 1000s of hours
Next week I am running a short full load test on an Engine that’s 4hrs flat out just to check the installation is acceptable.

[Chris Cringle]

I gotta agree with the poster who advised to not buy a sailboat with an inboard gasoline engine. And to those who spoke up in defence of the Atomic Four, I ask, have ever seen, up close and personal, a gasoline explosion aboard a boat? I have. Find a boat with a diesel inboard, an outboard, an electric motor, or no engine at all.