Pulling the trigger on new motor...help please.

[nzmal]

My wife and I are about to put the deposit on a new engine for out Cavalier 39 yacht.
Specs are
GRP 9 Ton displacement
LWL 29'6"

She still has her original 1975 Volvo MD3B 36hp engine which is well tired now.

We're sold on a Beta but hovering between a 43 and 38.
The 38 weights 100kg less and is slightly cheaper (but not cheaper enough for that to be a factor)

We're currently running a 16" three blade prop on the Volvo but its left handed so a prop change is required.

The 43 will require an 18"
The 38 will use another 16"

We initially thought that the boat wouldn't take an 18" prop but just read the original spec sheet and see that it originally was fitted with an 18 inch 2 blade.

...because of the prop sizing we'd decided the 38 was the way to go, but now that it appears we can fit an 18 inch the 43 is back on the table....


.....arghhhhh.

Is there likely to be a huge difference in performance taking the 43 over the 38? Can anyone provide me with some sensible thinking here?

Thanks
Mal (New Zealand)

[robert sailor]

I'll leave the rest of your questions to others but I can tell you your choice in motors is a good one.

[kentobin]

Beta does have a service where they'll recommend an engine and prop for your boat.

I have a 37 foot cutter rated at 12 1/2 long tons.

I was considering the Beta 43 but they felt it would be a problem fitting it into my existing engine compartment without a redesign. I have to admit it they might be correct. Even getting it through an existing hatch might be a problem.

They recommended the Beta 38 but I'm leaning toward the 35 as it runs at a lower rpm. I read the only difference between both engines is the cam in the fuel injector pump is different.

They took 3-4 days to get back to me after my query.

The Beta distributor I dealt with is located in Sausalito, California.

[nzmal]

Thanks Kentobin

I can't help but feel I'm tripping myself up with the "more is better and i need more" trap when it comes to hp.

i had a look at a 38 at the Beta dealers yesterday and it's certainly a nice compact engine. Way smaller that the old Volvo and it should be a heap easier to crawl around. The 43 is close to the size and weight of the Volvo MD3B.

My max hull speed is a touch over 7 knots and a 38 should easily get me there...
Max torque curves are
Beta 38: 70 ft/lb @ 2300 RPM (producing 28 hp)
Beta 43: 95 ft/lb @ 1800 Rpm (producing 34 hp)

This seems to be the biggest difference... where/ when do I need that extra torque?

[Sailmonkey]

Did you ever feel starved for power with the old engine?

If not I’d be inclined to go smaller and easier to service.

[nzmal]

I hear you Sailmonkey.
This season the old Volvo wouldn't spin up without overheating so we were always lacking power... but at Sea trial and early days it would push us at hull speed.

We had a rough night with 60 knot winds and dragging anchor over Xmas and had difficulty motoring up to haul anchor... and this is clouding our rational judgement I suspect.

[a64pilot]

I’d go with the 43 myself and enjoy the lower RPM at cruise.
However be sure you don’t need to change the shaft too.

However if it’s just an overheating issue, likely you can fix that don’t you think?
As motors age, they due to lower compression produce less power, and therefore less heat, they don’t run hot from age.
Usually an old motor starts to run hot when things are fixed and she starts running better than it has for a long time, the new found power comes with heat of course.

[nzmal]

Overheating likely to be waterjacket issues. Done all the basic stuff but don't want to spend time and money keeping a 43yr old motor performing. It's never been reliable since we bought it 2 yrs ago and days were numbered then.
We're leaning to 38 for size and prop size reduction. 18inch prop possible but we're concerned lack of clear space may translate into cavitation noise through the hull..

[Jim Cate]

18inch prop possible but we're concerned lack of clear space may translate into cavitation noise through the hull..

IME a bit of extra tip clearance is a good thing. Less vibration coupled to the hull, better free flow to the prop, possibly less prop walk.

I'd expect better performance even from the 38 compared to an aged MD3 IF you get the prop right. BTW, what sort of prop are you gonna use? Two or three blade, fixed or low drag?

Jim

[nzmal]

Hi Jim
Prop hasn't been determined except it will have to be fixed blade since there isn't room for a folding one. Probably be a 3 blade 16 or 17 inch. I'll let the prop expert give that advice.

[GordMay]

Originally Posted by Jim Cate

IME a bit of extra tip clearance is a good thing. Less vibration coupled to the hull, better free flow to the prop, possibly less prop walk...

Indeed.
➥ Propeller Clearance Diagram - Cruisers & Sailing Photo Gallery

[NCboatrx]

Hi,

I have run a propeller calc for you based on the boat specs found here CAVALIER 39 sailboat specifications and details on sailboatdata.com

Assuming that you have quoted the correct weight at 9 long tons (20,000lbs) then you will still have plenty of power with the Beta 38. Go with the 2.45:1 transmission and a 17"x12" three blade propeller with 50% BAR. You should achieve just over 7 knots in flat water and you will enjoy the extra space in the engine compartment when you have service work to do. The 43 with a 2:1 transmission does not show to improve boat speed at all.

Stanley

[Kalinka1]

Originally Posted by NCboatrx

Hi,

I have run a propeller calc for you based on the boat specs found here CAVALIER 39 sailboat specifications and details on sailboatdata.com

Assuming that you have quoted the correct weight at 9 long tons (20,000lbs) then you will still have plenty of power with the Beta 38. Go with the 2.45:1 transmission and a 17"x12" three blade propeller with 50% BAR. You should achieve just over 7 knots in flat water and you will enjoy the extra space in the engine compartment when you have service work to do. The 43 with a 2:1 transmission does not show to improve boat speed at all.

Stanley

I'd listen to Stanley if anyone knows Beta's it's him.

[robert sailor]

Originally Posted by Kalinka1

I'd listen to Stanley if anyone knows Beta's it's him.

He should know them..he's the Beta distributor for the United States

[michaeld]

I bought my engine for my Cal 2-27 from Stanley at the Miami boat show in 2004. She has a new owner now, and the engine is still running great. If I ever have to repower my "new" (old) sailboat, I hope that Stanley will not yet be retired.