N90 in 8V71

[Timeless72]

Thanks in advance for the advice. We will be overhauling this off season and currently run N70 in our 871 naturals. I know N80 will work but could we jump to N90 injectors? Would this provide any practical gains? Boat is underpowered, so looking to get whatever we can while going to all the effort.
I searched the web and found a few bits about fire engines. Nothing about a boat. Thinking the only gain would be at WOT.

 

[Captain Ralph]

Thanks in advance for the advice. We will be overhauling this off season and currently run N70 in our 871 naturals. I know N80 will work but could we jump to N90 injectors? Would this provide any practical gains? Boat is underpowered, so looking to get whatever we can while going to all the effort.
I searched the web and found a few bits about fire engines. Nothing about a boat. Thinking the only gain would be at WOT.

I managed a 44 Striker with fresh 6-71Ns with N60s. Downhill, with the wind and some imagination, 16Kts wot. Sometimes lost plane going up over a swell. Picked back up on the backside (downhill).
We installed N90s. WOW.
We never got to ad pitch to the props but never had a problem again busting over a swell. Still clear exhaust. I was looking forward to adding 2" of pitch but boat sold before it came back to Jax.

Find a good injector shop, Rebuild yours with the N90 kits. Have them popped and matched and run with big smiles.
I have never had good results with off the shelf injectors.

 

[cww]

I had a very good experience with upsizing injectors on Detroit naturals. I put n60's in place of n50's in my 8v53's and picked up more power without any increase in smoke or any overheating problems. Never had any ill effects that I ever noticed. I don't know if this applies to the turbo models though, I've heard they don't have the excess cooling capacity to play with like the naturals do.

 

[Timeless72]

Thank you. At some point, the injector must be too big and wasting fuel but if we can get a little more power and clean burn, I am all for trying.

 

[cww]

Thank you. At some point, the injector must be too big and wasting fuel but if we can get a little more power and clean burn, I am all for trying.

From what everyone told me (and from my own experience doing it) going one size up is no problem. You won't notice the extra power most of the time because the only time it really comes into play is when getting the boat up on plane, at which point it's very noticeable. It's also noticeable when cresting over swells while on plane, the engines didn't struggle like they used to. Overall it was worth the couple grand it cost me.

 

[Captain Ralph]

Thank you. At some point, the injector must be too big and wasting fuel but if we can get a little more power and clean burn, I am all for trying.

Standard cam timing, Naturals (Non Turbo), standard blower drive ratio and fresh enough of an engine to run them in; The N90s are the largest you can install and still have a clean engine.
Also; It is better in 4 valve heads vs the ole 2 valve heads.

The injector groups get smaller when you lower the engine compression and change anything else; Turbo, Injector, Air cooling, Cam timing, Blower ratio, Blower bypass and more all get intricate with each other and the simplicity goes aweigh.

Since there is usually no throttle delay on Naturals, You may see a dark puff when you punch the throttles with the N90s.

 

[Avenger]

Thank you. At some point, the injector must be too big and wasting fuel but if we can get a little more power and clean burn, I am all for trying.

That's not how diesels work. It's all about loading and propeller demand. Bigger injectors without bigger props or more barnacles isn't going to change much of anything.

 

[cww]

That's not how diesels work. It's all about loading and propeller demand. Bigger injectors without bigger props or more barnacles isn't going to change much of anything.

It changes a lot in my experience. Putting aside the sole category of go-fasts, everything is usually propped to within an inch of its life based on factory testing that normally gets done with <1/2 fuel and water, very few people onboard, and missing the 3 tons of crap most owners inadvertently add to the boat. I know I'm guilty of that myself. By the time you have a bunch of clothes, rods & reels, pots and pans, liquor, mixers, dinnerware, glasses, rugs, pictures, lamps, tv's, stereos, etc., etc., etc., most large boats are furnished like houses, and the boat will barely turn rated RPM going downhill with a tailwind. By the time a second or third owner comes along adding even more crap, the problem just gets worse.

In my case, going up a size in injectors got me rated rpm at all loading conditions, and eliminated a lot of my struggle getting on plane. It was worth it. I'm sure your response is I should have put the boat on a diet, and you'd be right. I have no defense to that, other than my better half has to like the boat and I'm not the one responsible for most of the stuff onboard. It was a solution that worked to get up on plane. Arguably it wasn't the best solution, but I was working with the hand I was dealt there.

 

[Timeless72]

Our situation too and appreciate the input. What was once 23 tons is likely close to 30 with full fuel and water, corian counters, furniture, etc. While she will never be a speed demon, I like to get places and relax. Until we retire, anyways.