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Discussion in 'Diesel Engines/Drives/Transmissions/Props' started by SEAWOLF, Dec 8, 2021.
My friend looking at Sea Ray boat with Cat 3116 300 HP engine . Need real world inside.
Search is your friend here ;-)
@SEAWOLF 1998 3116's 350hp. Owned them for 4 years, very happy so far. Approx 1700 hours.
Many of us own these, many will chime in. Keep the fuel clean, don't let the engines overheat, change your oil and filters, and they run. Depending on the age, there is a major service at 2000 hours to be aware of.
Would buy a boat with these again with no question.
Great Engine period.
What he said ^^^
first diesel engines for us, similar to the 3116 but we have 3126. Absolutely love them, the power, efficiency, sound and smell (personal preference ), etc.
I notice the OP said 300HP, folks are replying with 350HP though. Typo by the OP?
The 300 hp and the 350 hp 3116's are almost identical except for fuel pump and injector settings and perhaps the turbo charger.
The 3116 's are very low maintenance engines. There are very few recommended procedures……@250 hours, reset the engine overheads- takes about 8 hours; @ 1000 hours have the after-coolers and heat exchangers cleaned cost varies depending upon how the technician cleaned the heat exchangers; @ 2000 hours, reset the overheads and clean the after-coolers and heat exchangers, again about 8 hours, plus the cost of the after-cooler service which will vary depending upon how the technician cleaned the heat exchangers.
Depending upon which Sea Ray your friend is contemplating, the boat could be a bit underpowered with 300hp engines. If that is the case, then be sure they turn up to 2800 rpm at WOT and don't cruise the engines at more them 2400 rpm, which is recommended cruise speed for the 3116. If they won't turn up to 2800 rpm, then limit your cruise speed to 86% of the WOT the engines will develop, until you either lighten the load or have the props re-pitched.
All in all, these are nearly bullet proof engines as long as you don't not over heat or overload them.
I didn't know SR installed any 300HP's; thought they were all 350. Learn something every day.
"And don't Cruise the engines at more than 2,400 rpm"
This is what kept me from buying a friend's 1998 400da with twin cats. He used to brag how hard he ran the boat. Plus they had over 2,000 hours with no service history at all other than his word.
I know you can pull these rpm numbers off of a gas engine (how many hours at what RPM range), can you pull them off of these cats? If you can't how do you know you're buying a boat where the owners kept to this?
Most if not all the CATs of that era are mechanic diesels, no electronics so you cant "pull" the history. The only way to tell anything is to have them surveyed by CAT. In the end these either run or they do not run, not much in between.
Not sure what "hard" is, but these are pretty robust engines. CAT expects these 3100 engines to be run at WOT at least some of the time, I think the E spec is 8% of the time, so 5 minutes out of every hour, and the engine hours to be somewhere between 250 and 1000 annually. Not many of us are even getting close to that. These are likely 10,000 ++ hour engines if well cared for. They don't like being run at idle speed for long periods either.
Make sure they are not over propped then...Start 'em up, warm 'em up, and run them. Spend the majority of the time at a reasonable cruise RPM (2000-2400, CAT recommends 2400), but also at WOT if the situation dictates (within reason).
I think about the only way to abuse these engines would be to run them WOT all the time every time out, but I cant imagine any reasonable owners doing this as the fuel economy would suffer horribly, negating one of the major reasons to own a diesel boat.
Hard means he ran pretty much at WOT all the time.
That’s not just hard, that’s just plain dumb.
Even with that, the engine is probably fine, but the longevity will be decreased, and more MX required. If that info is known, you a right to steer clear.
With that said, running a diesel “easy” can have the same deadly effects.
how would you know if your over propped? you cant reach wot?
Correct. Especially with the older mechanical diesels. Typically you want them to spin up to the rated RPM +25 to 50 as you run the boat, fuel water people gear etc with a clean bottom good props. Thats 2800-2850 for the 3100 CATs. The Cummins also have a specific fuel burn to be under to prolong the life of the engine.
If you're a member on boatdiesel.com, there is a prop calculator that allows you to crank in your boats engine/transmission/weight and WOT readings (must be accurate, don’t trust stock SR tachs), and it will give you a curve of how much you are over or under propped. Ideal is right on the curve…not lugging the engine, and also not wasting fuel if under propped.
SBmar.com has lots of information on the Cummins side of things.
Or see what your boat pulls then take the props to your prop shop and tell then you need XX more RPM and they know what to to.
I had my props cleaned and tweaked. I couldn't go over 2650. now I'm at 2850 with the sync on. I was thinking of maybe pitch it one degree or have them cupped
FYI, when on the sync on my boat, at WOT the sync kicks off and it's a hard turn...