engine horsepower

[sailorman]

My boat has a 16-18hp 3cyl perkins running a 13"x 8 pitch 3bladed prop. Her displacement is 3.2 tons and she is a long fin keel (6-7ft long) her hull profile is identical to the Elizabethan 30. her max speed under engine is 5kts in slack water, but when punching into any choppy she struggles to top 2-3kts and can very easily fall far behind when in the company of a Snapdragon with a 1GM10 and a Foxhound with a 15hp outboard, although she can easily outrun them under sail.
Why is she so sluggish under power, could she be under proped, needing more pitch, or under powered>
I have been told that if an engine (Diesel) does not give an initial puff of smoke when fully opened up then she is under proped.
What does the board think?
C_W

if it over revs = under propped
if loadsa black smoke & doesnt increase revs no matter how much more throttle you give it = over propped
she should give hull spd (or a little less ) @ max rated revs

 

[Clyde_Wanderer]

if it over revs = under propped
if loadsa black smoke & doesnt increase revs no matter how much more throttle you give it = over propped
she should give hull spd (or a little less ) @ max rated revs

I would be safe saying that she will happily rev from half to full revs without any marked loading or much increase in speed and certainly no smoke.
Dont have a rev counter so cant be precise reg working revs etc.
C_W

 

[LittleSister]

Plus you'll struggle to buy an auxiliary as small as 10hp these days; I can't think of any smaller than 15hp.

Beta do a 10hp (as well as the 13.5hp mentioned earlier).

 

[sailorman]

I would be safe saying that she will happily rev from half to full revs without any marked loading or much increase in speed and certainly no smoke.
Dont have a rev counter so cant be precise reg working revs etc.
C_W

sounds like you have an "Egg Whisk" & seriously under propped

 

[PetiteFleur]

Plus you'll struggle to buy an auxiliary as small as 10hp these days; I can't think of any smaller than 15hp.

Beta Marine do a 10 & 13HP x 2 cylinder diesel which is excellent.

 

[Clyde_Wanderer]

sounds like you have an "Egg Whisk" & seriously under propped

Been thinking that myself, though other than a larger pitch there is not much I can do about it as at max prop dia due to skeg clearence.
C_W

 

[Bosun Higgs]

New to sailing so forgive my novice questions but have been looking at a few cruising yachts one that i like has a 10hp bukh engine would this be enough to push along a 26ft nearly 4 ton boat,not in a hurry but thinking more about having plenty of power for getting out of trouble.Do different engines tend to drive boats better than others.
help appreciated

You'll hear a lot of chat on here from the "purists". The reality is that you will do far more motoring than you expect ( I reckon to average about 50% and that isnt unusual if you are going somewhere as opposed to pottering or racing) so you need a good sturdy engine with a decent output. 20hp for a boat of that size. 10 hp is marginal.

 

[simon597]

there are still some Yanmar 1gm10's about good lump last for ages and spares are a plenty, plus people are selling on ebay and classifieds and you can still get new if you look ? just get the right ratio g/box and prop to match. But really please for the love of god don't use a BETA you'll regret it......

 

[LittleSister]

But really please for the love of god don't use a BETA you'll regret it......

Why? (He said not regretting his yet.)

 

[Babylon]

But really please for the love of god don't use a BETA you'll regret it......

Why, exactly, please?

 

[Haven't-a-Clue]

there are still some Yanmar 1gm10's about good lump last for ages and spares are a plenty, plus people are selling on ebay and classifieds and you can still get new if you look ? just get the right ratio g/box and prop to match. But really please for the love of god don't use a BETA you'll regret it......

Well, admittedly, the heat exchangers' can be a PITA to keep clear, but I wouldn't say never have one..........unless you've had some other problem with one?
I (obviously!) have one, so do tell

 

[doug748]

Been thinking that myself, though other than a larger pitch there is not much I can do about it as at max prop dia due to skeg clearence.
C_W

I know nowt, but 8in pitch sounds a bit spare.

There is an outfit (in Poole I think) that will re-pitch your prop for you, they can only do it once.

 

[Tranona]

Been thinking that myself, though other than a larger pitch there is not much I can do about it as at max prop dia due to skeg clearence.
C_W

Put your boat's data into the Propcalc programme - free on www.castlemarine.co.uk This will give you a good guide. Does sound underpropped. If Propcalc does suggest a coarser pitch you can probably get it repitched. Any Prop specialist will do it - there are plenty of them around and probably one local to you. Best then to ask their advice as most will have the experience to know what is best.

 

[richardh10]

My boat has a 16-18hp 3cyl perkins running a 13"x 8 pitch 3bladed prop. Her displacement is 3.2 tons and she is a long fin keel (6-7ft long) her hull profile is identical to the Elizabethan 30. her max speed under engine is 5kts in slack water, but when punching into any choppy she struggles to top 2-3kts and can very easily fall far behind when in the company of a Snapdragon with a 1GM10 and a Foxhound with a 15hp outboard, although she can easily outrun them under sail.
Why is she so sluggish under power, could she be under proped, needing more pitch, or under powered>
I have been told that if an engine (Diesel) does not give an initial puff of smoke when fully opened up then she is under proped.
What does the board think?
C_W

I have an Elizabethan 29, and I am also having a few problems with my 19hp perkins perama. It goes along nicely at 2000 rpm, but as soon as it goes over that the engine loses power. Have been wondering if it is a gearbox problem, but could it also be a prop problem?

 

[Spyro]

Eamonn, speak to the prop guys at Rothesay dock.
There's definitly something not right. I have 18hp and a good bit heavier and I can cruise at 5.5knts (on gps) in flat no wind conditions. I can push that up to 6.5 at full throttle.
Is this a recent problem? I seem to remeber you motoring faster than that on the way to Tarbert 2 years ago. Does it go faster if it's getting near to closing time?

 

[Tranona]

I have an Elizabethan 29, and I am also having a few problems with my 19hp perkins perama. It goes along nicely at 2000 rpm, but as soon as it goes over that the engine loses power. Have been wondering if it is a gearbox problem, but could it also be a prop problem?

Should be able to run up to 3600. If it does that in neutral but not under load then it is almost certainly the prop - either heavily fouled or too much pitch. Expect you will find diameter constrained by clearance, so will have to adjust pitch. Suggest you use the Propcalc programme as in my reply to CW above, or give the same data to a prop specialist for a recommendation.

 

[richardh10]

Should be able to run up to 3600. If it does that in neutral but not under load then it is almost certainly the prop - either heavily fouled or too much pitch. Expect you will find diameter constrained by clearance, so will have to adjust pitch. Suggest you use the Propcalc programme as in my reply to CW above, or give the same data to a prop specialist for a recommendation.

Thanks for that. It will run up to 3600 in neutral, but as soon as I put any load on it over 2000, it seems to stop working. I'm coming out on to some scrubbing posts next week so I'll have a look at whats going on

 

[simon597]

Sorry for leaving a statement and not explaining myself I was working at sea for a while, right personal experience only here,
My Customers have had heat exchangers and water pumps die in annoying ways, yes they clog as do most but when you come to clean out heat exchanger for example I've not managed to save one as they normally corrode around the seal area so damaged that it makes no sense to clean and rebuild, I guess you do get what you pay for and there is a reason that beta marine are cheaper than some in the market place they use lesser metals and "seem" to suffer after a short time in the sea environment, inland water ways no issues but at sea seems to be the killer of the ancillary parts, as lets face it the engine block(pistons, crank, crank case etc.) are normally a mass brought item, some are kubota and some Mitsubishi so all in all and opinion and after repairing many I guess I've come not to like them sorry all and yes yes some will comment but please its only an opinion that you'll regret having one in a few years !!!

I'm now expecting people to tell me their engines do that and they're not beta or that their's aren't like this etc..... well come on then share ????

 

[Grumpybear]

Thanks for that. It will run up to 3600 in neutral, but as soon as I put any load on it over 2000, it seems to stop working. I'm coming out on to some scrubbing posts next week so I'll have a look at whats going on

If this is a new problem and you've had the boat a while, it's unlikely that the prop has suddenly changed, although fouling might explain it. try looking at the air side: air filter if you have one, exhaust elbow, exhaust hose etc.

 

[Baccarat]

10hp on a 26' boat is more than appropriate, I would suggest! About 30 or 40 years ago, it would probably have been about 6 or 7 hp!
My Hustler 25.5 has a vetus 11hp, with a folding prop, she will push to 7kts, at full power,and comfortably makes 5kts at about 65% even against the wind in the corinth canal!

I realise a long time after your post, but what diameter and pitch prop was that with?
I also have a 25.5 with a folder and a 10hp engine and at present can’t get close to 7 knots.