Mainship 31 purchase advice

We have an offer in on a 2005 Pilot 34 with twin Yanmar 240s. Does anyone know the fuel burn on a boat equipped like this?

Ljk
Have a good look at the exhaust system for drainage into rather than out of turbos. Water ingress into #6 cylinder can be an issue. Dave Marchand knows well of this subject.

I will note this to the engine surveyor, thanks sunchaser!

I can't speak specifically about the twins, but in pictures I have seen the exhaust geometry is similar to the single. And many surveyors don't pay much attention (just like boat builders) to this problem.

Here is what you can do to check it yourself:

Look at the mixer- the stainless steel device where raw water mixes with the exhaust. It has an internal space where raw water enters and mixes with the exhaust at the end near the hose connection. Visualize what happens when the engine shuts down. Unless the mixer is oriented properly, the jacket will retain water. This will increase corrosion and if it ultimately fails inside, that water will run back into your turbo.

The other issue is height. Look at the height of the lower wall of the exhaust gas loop- the spill over point. That height should be at least 12" above the water line. You can easily find the water line by opening the strainer and noting the water height and compare it to the "spill over point".

The attached pic describes this graphically.

With the single, I cruise at 14-15 kts at 2,800 rpm and max out at about 19 kts at 3,300 rpm. The Yanmar twins are higher rpm engines- 3,800 max and should cruise at 16 kts at 3,200 rpm and max out a bit over 20 at 3,800.

It should burn about 15 gph at 16 kts cruise speed.

David

Thanks, David, much appreciated.

Other than relocating the engines or the mixer, is there any cure for this issue? Does Mainship know about it?

I had a similar situation with a 2002 Regal I owned. Ruined both gas inboards. The manufacturer ended up giving me 2 new engines. Luckily it was a new boat, under warranty.

ljk said:

Other than relocating the engines or the mixer, is there any cure for this issue? Does Mainship know about it?.

Click to expand...

Per Dave's post, the right mixer height is essential, few surveyors know or care about this issue so be vigil. Redoing the exhaust/mixer run to gain the height is a good idea - and costs a bit of $$. If the engines check out OK and you otherwise like the vessel price in the mixer/exhaust run redo to your negotiations.

Yes, Mainship knew but with their several years of financial issues no good recourse was available to buyers if problems showed up.

ljk:

The fix is fairly easy for the single- weld in an 8" riser extension and orient the mixer so it will drain. Cost less than a boat buck to have it fabricated.

But I don't know about the twin. At least on one side the mixer will be under the deck and not the deck opening. And is there room to orient the mixer so it will drain?

And since you asked, the lack of access is why I passed on a twin when we were looking.

FWIW I added a pic to my post above.

I can't say what Mainship knew or didn't know. But like your Regal it is a common problem. For 90% of owners they don't moor in conditions where water can back up. And for those that do get water backing up 90% of those don't know it, yet.

Mine backed up during the pre purchase survey haul out- the Travelift operator pulled the stern higher than the bow and water sloshed forward. I discovered it a few days later when I took delivery and did an oil test and it showed high sodium.

David

Excellent info, gentlemen, thanks again.

(The other issue is height. Look at the height of the lower wall of the exhaust gas loop- the spill over point. That height should be at least 12" above the water line. You can easily find the water line by opening the strainer and noting the water height and compare it to the "spill over point".)


David,
Pardon the dumb question but you open the strainer lid and measure the height of the water coming out of the strainer to the lower elbow?
Just want to make sure I'm understanding?

Well, I guess it only works if the strainer top is higher than the water line. But maybe you could measure the height of the water gushing out ;-).

David