Capricorn - C trial & log strike

[rsn48]

So in a previous thread I started, I talked about having to choose a prop with limited data (won't go into it here). And I realized I'd probably have to try out 1 to 3 props to get it right. I also wondered what the speed would be at WOT. The prop selector I used at the Mercury site ended up selecting an 18.75 D & 17 P, RH. The leg is a Bravo 2.

So five days ago, I went out on the boat for sea trials, two guys from the engine install shop and one guy from the refit guys business and myself.

Capricorn is 28 feet but a large 28. I guesstimated its weight with everything in at 14500 lbs for the prop selector at Mercury. The engine is one of their newly designed and engineered engine, not an auto or truck engine modified for the marine environment. The engine is gas and rated at 350 hp from a 6.2 litre block. The Merc prop selector predicted 34 mph.

So she was finally moved after 20 months back to the marina after being on the hard - forever. You can also imagine I was pretty excited and nervous about the boat's and engine's performance.

So the boat is launched, the motor started and away we go. We perform a number of zig zags to see how the boat will handle the engine and new weight with stuff added. The boat handles tight turns well. We go to WOT and the boat hits 31 mph at 5200 RPM so this impresses me. With the old Merc engine my top speed was 12 knots (the hp was 240 at the prop).

The engine guy had me take over and wanted me to "fling" it through some tight turns performing tight S turns. After about 5 minutes with me at the helm, I hear something hit the hull but not that loud. Only me and another guy heard it. But 15 seconds later a big bang, the engine leg flies up and the engine is rev high with the leg out of the water.

We look and see a log about 5 feet long and rough 10 inches in diameter floating away. My poor boat hadn't been out 20 minutes and already I was worried I had just incurred a many thousand dollar problem.

A couple of miracles that day:

1) the initial testing of the engine and leg right after the strike seemed to show no damage.

2) the guy who brought my boat by trailer hadn't left so we took the boat back to the trailer and upon pull out looked for damage anywhere on the boat, nothing found.

3) the prop recommended by the prop selector was bang on, I was very surprised and happy.

The next day I went out with my refit guy and immediately ran into a long line of wood debris at the tidal line of our spit. There was literally hundreds of wood "stuff" in the water, most of it short and narrow, less than two feet. But in the midst of all this little wooden garbage floating around were much larger pieces. I called a Securite on my radio to other boaters coming out. We fiddled with the boat, trying out hard turns in reverse, etc but decided to call it a day with all the crap in the water. Neither of us had ever seen so much wood garbage in the water close to the two Comox marinas.

So my initial sea trials are over, only to be informed I need to take the boat back to the engine guys to carry out the 10 hours change of fluid for a new engine & leg requirement. I was told I could take it out for 15 hours or so instead. Oh yeah, more money as the boat will be trailered back to the shop.

Anyway, the boat survived a log strike, the engine and leg survived a log strike, and my heart survived a log strike. The boat performed well and barring the obvious, I was pretty happy with the outcome.

 

[C lectric]

It's always nice when a plan comes together, other than errant logs. The boat got a heck of a test though.

 

[Frosty]

Wow, it's "new" boat. What a change in performance from the last engine.

That log strike -- what a sock in the gut right in the middle of your first outing. So glad it didn't cause a bunch of damage.

 

[Jeff F]

That sounds like a success story in lots of ways. You've got a package that you can have confidence in! Must feel good after all the work and planning.

 

[rslifkin]

Sounds like things came together well!

As you get some more run time with it, I'd do some prop slip calculations. If slip increases excessively when dropping from WOT to planing cruise, you might benefit from a prop with a bit more blade area and a little less pitch. You may or may not lose some WOT speed, but you'd likely gain performance elsewhere.

Of course, run it as-is for a while first to get a feel for if it needs more bite at lower speeds or if it's already got plenty.

 

[boathealer]

Wow!! I'm glad everything came out so well! I would definitely have had a heart problem......

 

[rsn48]

I was worried about a couple of things with the log strike. The hull is glass over plywood, very thick plywood (original build) but the glass is quite thin. Now they must have known what they were doing way back when, the hull is in great shape and trust me the inside of the hull was inspected very closely and in detail. But I was wondering how the thin glass would handle that big thump. No one could find any marks anywhere.

Second concern was the original I/O hole was glassed in and another smaller hole cut out. This is done from the outside, and several layers of plywood are peeled back to give more bite for the new glass. The log hit the leg which had to have stressed the new glass area, again nothing visible.

The original plan was to stay on the boat for 24 hours, this decision made pre-log strike to be there if anything (like thru hulls, etc) leaked. I extended my stay from Tuesday overnight to Friday overnight. The only flaw in my plan was the clothing I was wearing was all the clothing I had brought other than a sweater and jacket, keep warm material.

Due to a wooden keel running the interior length of the boat and given how tall it was, installing a tunnel bow thruster was out of the question so instead I went with an Exturn bow thruster which is under the hull. I was paranoid but only slightly that it had been hit. The reason I wasn't too worried is that when my boat goes up on plane, like most planing semi-displacements, the bow goes up and brings the thruster out of the water. The thruster was not damaged. I am going to give a very short review of this thruster in another thread, but link below to what I installed. But a quick comment, I was much happier with it than I thought I would be:

https://side-power.com/kategori/183...l-itklJKYrsHItSMQLqazkeXb5ulUyxRoCLIMQAvD_BwE

 

[O C Diver]

Change the lower unit oil and check for metal on the drain plug magnet. What happened to the outside of the lower unit housing may not correspond to what happened on the inside.

Ted

 

[rsn48]

Because the engine/leg is new, Merc wants a 10 hour service which my engine guy said I could extend to 15 hours which I am going to do. I will have the drain plug magnet checked.