Cummins Sea Trial

When we eventually felt we had the engine installed and everything hooked up properly we scheduled the sea trial with Cummins. Basically the situation is you buy the engine from Cummins, and in order to use the engine they need to sea trial it so they can “enact” your warranty. You can install the engine and off you go, but without the sea trial by Cummins you’re flying without the warranty.

The sea trail consisted of a mechanic coming to the dock, looking the engine over from head to toe, and then going for a ride with all sorts of testing gear hooked up to the engine. The looking over was pretty basic and good thing to cause we had the hose for the drip less stuffing box hooked up to the fuel return!! I know this sounds incredible, (and I don’t mean any disrespect to anyone because I understand why things are the way they are) but the instruction book Cummins gives you is pretty much worthless. It tells you things the engine must be able to do, but it doesn’t really tell you how to install the engine. The mechanic was a really nice guy and he helped us get that straitened out. (another thing in our defense is there’s all these quick connect fittings on the engine, and these are for his testing gear, not for the operation of the engine, so that was another factor in our confusion).

Another problem we encountered was he was not satisfied with the linkage I had for the shifting of the gear. The throw was not as pronounced as he felt is should be, (and I agreed with him). Took me almost an hour to get it satisfactory and he was quite helpful and very patient as I got that fixed.
Once all that was set off we went; it was a beautiful calm day. The first thing they check is your ability to get to wide open throttle. If you can’t get to wide open throttle, which for me was 2,600 rpm’s they just turn the boat around and call it a day; that’s it. So, as you can imagine I was a little nervous about this. I had a brand new prop on there which was a whole different beast than the old one so it was anyone’s guess on the size and pitch. The other thing I was a little nervous about was the size of the engine. At 305 HP it was bigger than any one I had ever heard of in a Mainship 34, and truth be told I had to listen to a fair amount of nay sayers about putting an engine that size, in this boat. (Luckily I had an equal amount of pundits telling me I was nuts not to go with the 305 HP)

Once we got out there, the mechanic told me to just put the hammer down. Up and up the rpm’s went and at first I really didn’t think we were going to make it. But low and behold the meter did climb and we topped out at 2,620; “You just made it” came the dead pan response from the mechanic. I had a small gps with me and at the 2,620 it read 20.6 knots. It was a little unnerving going that speed to be honest, and as I have come to learn since then the boat has no trouble up to 17, 18 even 19 knots in calm seas, but at 20 you really need to be on your toes, and its not a neighborhood you really want to hang around in to long. So, I was very relieved when finally told me to back it down.

After that the mechanic gets right in the engine bay (thank god you can steer a Mainship from below cause I have no idea how we would have conducted these tests with one guy on the fly bridge and the other below) and hooks up all kinds of gizmo’s and you run the boat bumping it 200 rpm’s at a shot. He would run his tests, then nod to me and I would go up 200. At each interval he tests for fuel flow, water flow, fuel return, exhaust back pressure, temperature and all kinds of other stuff I don’t really remember. One thing I want to stress right now is if you ever go through this, and the mechanic offers you ear plugs; take em! I did not and the sound of that turbo charger, with all the engine hatches up, when you get way up in the rpm range, is piercing. My ears were ringing all the way back to the dock.
The last test we performed was engine room temperature. It was not a perfect test as I still did not have any interior in the boat so there was a bunch of circular holes on the outboard sides of the floor that were open. (Interior would cover these thus cutting off air flow) I wanted some sense of this item so I covered them all up with towels and other stuff I had on board. The result was I was 10 degrees over what they specify.

Well we got through all that and we headed back to the dock with both of us up on the fly bridge. One thing we did notice when we were up there was some vibration between 1,000 and 1,400 rpm’s. I did not notice anything unusual looking at the engine throughout all the rpm’s during the testing, but it was definitely noticeable up there.
Once back at the dock, we were met by the regional sales manger that went over everything with the mechanic and it was all documented in this paper work he had; then we all signed it. The areas I failed in were noted; engine room temp 10 degrees to high, I did not have this small strut the exhaust elbow came with installed properly (actually didn’t know what it was) and the area available for air entry was way under. I needed almost 200 sq. inches and I only had about 90. So, end result is I could use the boat, but had to submit at some point what changes I made to address the issues noted.

All in all I was pretty relieved. The vibration was a bit of a bummer, but it was manageable for now, and I’m pretty confident I can fix it. At the end of the day, after working on this project since December I just wanted to go do some boating; and that’s what I did!