I'm choosing a Beta engine to replace my 1986 Volvo 2003 engine in my 18,000 lb Coast 34 (Graeme Shannon/Bruce Roberts designed) sailboat. We're figuring it will have 20,000 lb displacement when we are loaded for offshore cruising next summer. Dealers tell me the existing V-drive can be reused.
Since we are going to cruise the South Pacific/New Zealand area and maybe not come back I'm thinking the extra power of a Beta 38 would be useful. The boat's bow design, 11.5 foot beam and modified fin keel means that waves and wind push it around some.
I am not familliar with the Coast 34 so cannot comment on the actual installation issues that will be peculiar to this vessel.
The Beta 38 is a longer engine than the 2003 Volvo so there may be some installation issues because of this. The Beta 30 has much more power than the 2003 and may be the engine that you should look at if your engine compartment is at all tight. Measure very carefully before ordering. Both engines will move the boat well.
Please let me know the waterline length of the boat and the transmission ratio. I can then use this information to run some propeller calculations for you.
Hi Stanley. Most people aren't familiar with the Coast 34. It is the same mold as the Roberts 341, but a lot of times this doesn't help people place it either. The waterline length is 29'4" although that isn't fully loaded. I don't think we'll have a problem with engine removal and replacement as we have measured our companionway carefully and it looks like we can replace the engine by lifting and lowering straight out. The engine compartment length is 40" and we've looked at the engine measurements and think the Beta 38 will fit. Of course it will fit "backwards" since it is a V-drive so we will probably see if we can move some maintenance components to a different location.
The main issue between a Beta 30 and Beta 38 (as I see it) is that we're going to be cruising offshore and we've heard from many bluewater cruisers that its good to go for more power rather than less, if possible. Of course I don't want to overpower, but the boat is heavier than many of its size and I've read posts on this forum saying that the Beta 38 will cruise well even at lower rpm's should we wish to do that.
The original prop for the boat was a 16x12 RH prop (1" shaft). We currently have a 16 x 14.5 RH fixed 3-blade prop. We may go for a Max Prop. The V-drive transmission has a 2.37:1 ratio. The bearings were replaced several years ago so we are intending to keep it. While people have told us that it probably is made by Borg Warner or some other company, the nameplate on the tranny says Volvo Penta MS2V #KGMS2V. Would you have any idea about who actually made it? Thanks for your help.
Your transmission is a Volvo transmission but the spline and bolt up is the same as the 120S saildrive. This allows us to use our 120S saildrive adaption to fit your transmission to our engine.
We can adapt the engine for your access by fitting a raw water pump that is accessed from the transmission end of the engine and by fitting a remote oil filter.
According to my prop calc program, the Beta 30 wants a 16"x11" three blade prop for an estimated boat speed of 6.7Knots. Using the Beta 38 the program calls for a 17"x11" three blade with an estimated boat speed of 7 knots. Either engine will run well at low speed. If you want large alternator output and mabye a refrigeration compressor, it makes sense to get the 38 instead of the 30 so that you have an extra reserve but in reality, either engine will give your boat a good cruise speed. The 30 will give a better range as it is slightly more economical that the 38.
We have had excellent results with the Max Prop on different boats. I suggest that you contact Fred at PYI to get him to run some propeller calculations for you as he knows the Max Prop better than I do. I worked on a waterline length of 28'4" and a boat weight of 20,000 lbs for my calculations.
I found the boat specs on the Bruce Roberts website and I used the waterline length that he claims in the boat specs. This is 28'4". Here is the link http://www.bruceroberts.com/public/HTML/descriptions/Roberts341_description.htm
Good Morning. Can you tell me how important it is to have the true in-the-water LWL to calculate appropriate propeller size and engine? I have published material that shows both LWL measurements. As you say, Bruce Roberts' website says 28'4" and 20,000 lbs, but I have other seen different measurements and know that the displacement varies. If this is truly important, perhaps I should measure the boat as she sits right now (of course, fully loaded she will be a bit lower).
Or, are the calculations based on design size?
Please understand that I'm not trying to be argumentative or "right"here - I just want to be able to purchase the appropriate equipment for my boat.
Good Morning. In the interests of more information is better, we measured the boat last night in the marina, calm conditions, and came up with a LWL of 29'2". Annie
The extra bit of waterline length doesn't make any differance to the prop calc. (16.2" diameter to 16.3" diameter and this differance is too small to make a prop change).
Boats do vary a bit from one to another, even when made in a mold. These are all hand built and thus there are minor differances. As your boat will at times have different loads on it (for example - more stuff at the beginning of a voyage than at the end), you have to compensate for this. A prop calculation is not an exact science and has to allow for these variances. You will get the best results from your engine if you can achieve max RPM in gear when the boat is underway. This allows you to get the max HP that you have paid for into the water. While under power, as the boat speed increases at a given engine rpm, the propeller's efficiency increases and the slip decreases.
When you buy a propeller, the engine supplier and the prop company that you work with will do their best to provide you with the correct combination. If the prop needs to be tweaked a bit (1" more pitch or less pitch) to get the best performance, generally this will be attended to immediately. Having said all this, I would now use 29' for your prop calc to have the best chance of a good result.
Hello, Stanley. I've been assuming that the Beta 38 versus the Beta 35 is the correct choice for my boat, but another Coast 34 owner has recently questioned that assumption. He says that a Beta 35 installation would be propped for 2800 RPM and given that 90% of the time I would not be cruising at hull speed, I would find myself at 2000-2500 rpm where "the noise, vibration and fuel economy for the 35 are optimum...but I still have an engine which can achieve its max rpm and rated power".
I've searched this forum and haven't found much discussion of the Beta 35 versus the Beta 38. It looks like the same engine, except the 35 is derated to a slower speed, presumably because this is desireable. I'm curious about which engine was developed first and the pros and cons of each. I am working with a dealer in the PNW on this, but you have such knowledge of these engines I would be interested in your opinion of whether the Beta 35 might be a better engine for our boat and cruising plans. Price is not a factor, really, as there is only a difference of $250 or so between them. We are going with a max prop. This past weekend we took the boat to Port Townsend to consult with a mechanic on installation. The Beta 38 will fit just fine in our engine compartment.
The 35 and 38 are the same engine but the 35 has a different fueling arrangement than the 38. Because of your prop diameter limitation and the Volvo transmission ratio, I would use the 38 on your boat to get the most efficient propulsion system.
