2006 38' Admiral Prop Replacement

[Act Three]

Been lurking for a while an finally feel I have something worthwhile to contribute. Hopefully this information will come in handy in someone else's decision making in the future, and perhaps to all Admiral owners.

My wife and I purchase a 2006 38' Admiral catamaran last June. She was formerly called Wandering Rose for you Carribean Cruisers who may have seen her. Will be called Act Three going forward. Went to view the boat in Florida and meet the lovely Canadian couple who owned her last June and had the boat surveyed the next day. The previous owners had included a very detailed spreadsheet that held all information on boat maintenance for the last fours years so we were hopeful that the boat reflected the meticulous care put into the record keeping. It did. Boat did very well in survey, no osmosis, quite clean, with lots of extras for the cruiser. The couple had just completed fours years in the carribean.

The biggest issue during the survey was the sea-trial. The engines on the boat are Yanmar 3YM30's with with the SD 20 attached for propulsion. According to Yanmar the max RPM's are 3600 and cruising RPM is about 2900 (3600 *.8). During sea trials we could not get the RPM's to 2800 or so and she overheated 5-10 minutes into running her that hard. The former owners said that happened to them when they surveyed years ago and they had the heat exchangers cleaned and never had a problem in their four years. I think they we kind to the engines and never really put them through the paces of running the engines at proper RPM. 2400 RPM at about 5 knots seemed acceptable to them. The surveyor suggested that the props might be oversized and replacing the blades would fix the problem and be better for the engines.

For those less familiar with diesels and how they like to run I have learned that a diesel engine likes to run hard and hot with stress on it. Idling these guys is not good for them. I like diesels and have lots of faith in them. I also knew there were a lot of 3YM30's out there running well with SD20's attached.

We did purchase the boat and brought her up to the Chesapeake offshore and then ICW from Moorehead City due to weather. Motoring was slow but consistent, 2400 or so at about 4.5 to 5 knots when needed. Did a lot of power sailing with one engine and used little gas.

When I bought the boat I was pretty convinced the surveyor was onto something. When we got back home I started to do research. I called Yanmar and their engineer listened to the parameters and problems and thought too it was over propped. Called Flex-o-Fold and asked them what size prop SHOULD be on that Sail Drive with that engine. They reccomend a 16" with 13 pitch. They were great via email and sent me pictures where I should find the size and pitch numbers stamped in to the propellors. It was described to me that an oversized prop is like getting on a bike in 10th gear, working real hard but going slow with lots of stress on the engine.

Pulled her in November and discovered a big number 17 where diameter was to be, never found the pitch number. Ok possible correct decision, ordered the new prop blades (FYI came within a week from Flex-o-fold in Europe). In this case the 2006 prop hub was still current enough and all I had to replace was the blades which is really pretty easy. We also attacked some other issues (remember its a cat so we got to do this twice!!):

1. Replaced SD 20 Seacock with 3/4" Groco flanged seacock with backer plate
2. Replaced both hoses, 1 coolant, 1 fresh water
3. Replaced Impellers
4. Dismantled Exhaust manifold and removed and cleaned heat exchangers and exhaust manifolds.

Put her in the water and nothing leaked, win 1.
Had to work a couple of air bubbles out of the system when we started the engines but they both started up and pumped water (more water than before?), win 2.
Headed out to test results. Conditions were 5 knots of wind, less than 1' of chop, good conditions for motoring. Here are my results

RPM Speed in Knots
1800 4.0
2000 4.4
2500 6.5
2900 (Cruising speed) 7.5
Wide Open 8.6

Win 3

I now feel the engines will run longer and cleaner with better fuel efficiency and faster boat performance. A big part of this lesson to me was that the props were factory installed in the Admiral 38. Somebody in South Africa tried to get a little more out of the engines by specing a larger prop and the result was an underused engine working harder to perform worse.

Hope this helps others out there. Would enjoy feedback.

Now its just the standing rigging, sails, lifeboat, dingy...

We're about a year away but will see you all soon.

[Sail KiKa]

Hi Act three thanks for sharing!

I have been looking at the 38 Admirals now for some time and had one out yesterday for a short sail.

What year model do you have? Have you had any issues thus far? Would you recommend it?

The one im looking at has been chartered so sadly a little wear and tear on the aesthetic side but i believe mechanically quite good.

Appreciate your views.

Thx Marius

[Act Three]

Hi, Marcus,

Welcome to the forums. I am new as well.

We purchased our 2006 Admiral 38 Executive in July 2018 and have been refitting more than sailing this past year in preparation to go permanent live aboard in the next 12-18 months.

I did move the boat from Ft. Lauderdale to Baltimore, MD. last July with three others. We went offshore from Ft. Lauderdale to Beaufort NC where we were forced to take the ICW (due to weather) to Norfolk then up the Chesapeake to Baltimore. She did great in open ocean using just the Genoa and main (both original). Made over 11 knots at times in the Gulf Stream ( probably 2-3 knots help). Had some rather vigorous slapping under the bridge when offshore, noisy and shook the boat, low clearance. I expected this.

Due to her age we are replacing sails and standing rigging this year. The rep from Quantum sails was impressed with how well the sails had weathered the past 12 years. Yes they need to be replaced, but overall still had shape.

Ours has all the bells and whistles for offshore, SSB, radar, AIS, red and white saloon and cockpit lights, water maker, washer/dryer, dinghy Davits, asymmetric spinnaker, canvas cockpit enclosure, 2 AC units...

She is going through standing/running rigging refit now and news sails due mid-August. We continue to replace some plumbing fixtures and canvas pieces that have failed under normal wear and tear.

Point of interest, our stove is near port companionway, not facing bow, provides much better headroom.

Also the water and fuel storage (120 gal. Each) was a big plus. Another was the basket weave cabinet doors for better circulation.

Ours has two expired engine fire suppression systems. Don’t see that on many old 38’ boats. We are replacing ours.

By the way previous owners (2014 to 2018) sailed 12,000 miles and visited 29 countries in Caribbean and US over their 4 years. We hope to match.

Hope this helps, let me know results, happy to share.

Good luck. Matt