48 Yachtfish performance?

[brettportzer]

Do you have these tags on your valve covers still?

 

[drewread]

Do you have these tags on your valve covers still?

View attachment 76990

Nope, no signs of the options tags at all. But they were completely rebuilt in 2010 anyway - so literally anything could have been changed from those tags anyway.

I have reached out to MTU to see if they may know how to determine what he original options were.

 

[Eddieclemons]

Life is just too short to be working on someone else's boat. Get a contract on that thing if you don't already. Hire the Best DD surveyor you can find and then work your way through concessions for the needed work and or have the owner bring the engines up to spec? Good Luck, I hope you get your Hatt soon.

 

[drewread]

I have her under offer already, I wouldn't be wasting my time if I didn't. I've also had my mechanic out for a sea trial and am waiting on the oil samples to come back (we are also investigating another potential unrelated issue.)

She was not performing to her maximum potential for sure, which is why I'm here trying to figure out next steps to determine why.

From what I have read already in this thread (thanks all!) we should have done a no load RPM test. I'll make sure that is done when she heads for her out of water survey (assuming we get that far.)

If she hits 2350 RPMs no load then she is incorrectly propped.

If she only hits 1850RPMs at no load max RPMs, then she is governed to 1800RPM, then it would be time to open her up and determine if the N70 injectors and advanced camshafts are installed and if they are try increasing the governor to achieve the correct RPMs.

Thanks to all for chiming in with the information so far, it has obviously been useful!

 

[bostonhatteras]

I have N80 injectors with advance cam timing on my 871 naturals. We put them in. original was N70. on the pins we run full rpm 2300 + and temps are 175-180 with 27x30 four blade wheels

 

[drewread]

I have N80 injectors with advance cam timing on my 871 naturals. We put them in. original was N70. on the pins we run full rpm 2300 + and temps are 175-180 with 27x30 four blade wheels

Awesome, thanks for the detailed info!

Do you have your hull and running speeds with RPMs by chance?

I assume she gets up on plane just fine?

Did she already have the advanced timing cam with the N70s (was the advanced cam "stock" for the installation)?

Thanks!

 

[Timeless72]

I have N80 injectors with advance cam timing on my 871 naturals. We put them in. original was N70. on the pins we run full rpm 2300 + and temps are 175-180 with 27x30 four blade wheels

I had Lew on our boat this summer. Great guy. Full of conversation. He did mention the N80 injectors for more power. Do you know what you gained in HP with this set up? Appreciate the info!

 

[cww]

I have attached the Detroit Injector datasheet that nobody seems to want to read as an image, hopefully it is legible. If it isn't, then download the datasheet pages available above or in the first post.

It's not that nobody wants to listen or read what you post, the issue is like everybody has been explaining the 1,800rpm continuous-duty version was for generators. There is a 0% chance Hatteras installed one of those as the main engines in your boat. Every Hatt with 71-series Detroits came with the recreational marine version that turned 2300rpm. Most of us here have the same boats with the same engines in them, mine has 8v71's too. We're all pretty familiar with them. I think mentally you're in that phase of boat ownership where you found a boat you like and it's still new to you so you're bending over backwards to be positive about it. We all fall into that trap when we really want something, that's why it's a good thing that you asked for advice about it.

But look, the bottom line is you're missing 500rpm, and that isn't normal. Unless this is some smoking deal where you're only paying a fraction of its value, then I think your best course of action is to tell the guy to fix his own engines on his dime or else you'll reject the boat under the survey clause. If he won't find and fix whatever the problem is, then go find a different one that runs normally.

 

[cww]

I had Lew on our boat this summer. Great guy. Full of conversation. He did mention the N80 injectors for more power. Do you know what you gained in HP with this set up? Appreciate the info!

On my last boat that had 8v53's in it, I switched from n50's to n60's and it picked up noticeably more power, planed out easier, and my top end speed improved. It used to struggle to hit 2800 (the 53's are 2800rpm engines) and afterwards would hit the governors at 2850. I did not get any increase in smoke or overheating or any other ill effects that I ever noticed. I would definitely do it again except that my current boat has ti's in it and everybody always says that while it's no big deal to go up a size on the naturals, the turbos don't have the extra cooling system capacity to play with. So I've left it alone.

 

[Timeless72]

On my last boat that had 8v53's in it, I switched from n50's to n60's and it picked up noticeably more power, planed out easier, and my top end speed improved. It used to struggle to hit 2800 (the 53's are 2800rpm engines) and afterwards would hit the governors at 2850. I did not get any increase in smoke or overheating or any other ill effects that I ever noticed. I would definitely do it again except that my current boat has ti's in it and everybody always says that while it's no big deal to go up a size on the naturals, the turbos don't have the extra cooling system capacity to play with. So I've left it alone.

Thanks for the info. From what I know, 318 is N70. 333 is N80. Definitely a want but not need, given the price of 16 injectors.

 

[drewread]

N70 should be 333bhp @ 2300 N80 isn't listed for the 8V-71N Maybe someone has a newer dataset?

 

[cww]

N70 should be 333bhp @ 2300 N80 isn't listed for the 8V-71N Maybe someone has a newer dataset?

There probably isn't a product catalog out there advertising a 71 natural with n80's. The timing and performance data for the next size or two up of injectors usually comes out of the service manuals which also include info for the engines sold to the military. The military-spec engines usually had injectors that were a size or two up from the ones sold to the public, so the manuals will contain the timing and performance data for the larger injectors, if that makes any sense.

Some of the military engines also had different governors that if you turned some kind of emergency "battle" switch would allow the engines to rev up past their ordinary limits. I'm not sure what all the differences were, but that's where I got the timing data to put the larger injectors into my 8v53's and it worked fine.

 

[rsmith]

There probably isn't a product catalog out there advertising a 71 natural with n80's. The timing and performance data for the next size or two up of injectors usually comes out of the service manuals which also include info for the engines sold to the military. The military-spec engines usually had injectors that were a size or two up from the ones sold to the public, so the manuals will contain the timing and performance data for the larger injectors, if that makes any sense.

Some of the military engines also had different governors that if you turned some kind of emergency "battle" switch would allow the engines to rev up past their ordinary limits. I'm not sure what all the differences were, but that's where I got the timing data to put the larger injectors into my 8v53's and it worked fine.

I remember reading about aircraft having a safety wire across the throttle quadrant that was only to be broken in “war emergency” if it came back broken the engine needed a teardown. Lots of Detroits still in military use. When my son got to Afghanistan he heard that familiar Detroit sound. The APU cart for his aircraft was powered by a 12/71. Apparently it had been in service since Vietnam. It was at Baghram so the Taliban have it now.

 

[bostonhatteras]

As for Mil Spec governor settings etc, I believe they maxed at 2550 rpm. This includes fire apparatus too. at 2350 they sound like they will come apart, I can only imagine 2550. That type of tuning info is difficult to find on the internet but i might have it in print. I'll take a picture of my data plate and post it with the info on speed etc.

 

[bostonhatteras]

I remember reading about aircraft having a safety wire across the throttle quadrant that was only to be broken in “war emergency” if it came back broken the engine needed a teardown. Lots of Detroits still in military use. When my son got to Afghanistan he heard that familiar Detroit sound. The APU cart for his aircraft was powered by a 12/71. Apparently it had been in service since Vietnam. It was at Baghram so the Taliban have it now.

Buick 401 served in that start cart capacity too

 

[drewread]

Military fuels also change performances and operating specs.
US DOD burns NATO standard JP5 in about everything these days.

Well.. this thread has certainly drifted off topic. I'm not likely to be running my marine engines at MILSPEC on JP5 any time soon

All really interesting information, just off topic for this discussion - perhaps it should be in a new thread, because it is all interesting - it just just doesn't help this ol' 48YF get onto plane any time soon, or help to figure out why it isn't.

 

[SeaEric]

If you're expecting threads on this forum to stay on topic, you're going to be disappointed quite frequently! There can be some WIDE variation in where the discussion goes. Buckle up!

 

[johnjen50]

I just love that! Well said Eric!

 

[rsmith]

HOpE he DOseNt GeT UpSet if TiM PoWell cHiMes In

 

[madhatter1]

HOpE he DOseNt GeT UpSet if TiM PoWell cHiMes In

Hilarious. OP, it’s real. Extract the good info you need out of the thread and ignore what you want. Same as every forum.

Got to add the best forum I ever found (sorry HOF which I love) is the GTO forum where I get all my Pontiac technical info for my Firechicken. And even there you have to filter through “stuff “.

Gnomesayin?