New Boat - Engine Question

So, I bought myself a boat:

The engine is new, 225 HP Perkins turbo.
The boat cruises at hull speed at 1,600 RPM and turbo comes on at approx.2,000 RPM and is not much faster then. Hull speed suits me.

If I keep going like that the turbo will never spool properly; will this be OK or should I rev the engine periodically (how often then and how long?) to exercise the turbo? Max RPM seems to be 2,600 RPM.

That is a Perkins Sabre 225 TI I can only but assume without a few more pictures. The turbo is waste gated and starts to engage at around 1200 RPM. You can hear this especially when throttling back and turbo whine drops off. Max RPM is 2500. Your book has this information.

The engine should be able to pull 2500 RPM if it is propped correctly. Cruising at 1600 to 1800 RPM is the optimum range. Sure, run it up to 2000 or so RPM now and then, not really required too often if it is maintained properly. The temperature should stay in the 175 to 180 range.

Spend some time learning about the engine and required maintenance, it is a good one.

Plenty will say yes, you should rev her up for about 10 minutes every time you go out - personally I doubt it matters, just as long as she is got up to full operating temp for reasonable periods when you go out, the turbo will tend to look after itself. It is in the exhaust stream after all, so carbon build-up is hardly likely. Stopping the engine immediately after a hot on boost run would be far worse for it, although if it is like turbo cars these days, the turbo is probably water cooled anyway. However, still not good to switch off immediately after a full boost run, but realistically that would never happen, would it.
So, in my view, and I've owned (still do) several turbo'd cars, (not boats tho), I would say just happily keep doin' what you're doin'...

Janusz said:

So, I bought myself a boat:

The engine is new, 225 HP Perkins turbo.
The boat cruises at hull speed at 1,600 RPM and turbo comes on at approx.2,000 RPM and is not much faster then. Hull speed suits me.

If I keep going like that the turbo will never spool properly; will this be OK or should I rev the engine periodically (how often then and how long?) to exercise the turbo? Max RPM seems to be 2,600 RPM.

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At 1600 rpm what speed are you seeing in flat water?

Very nice looking boat by the way.. you should really love the layout and covered decks.
Thanks
HOLLYWOOD

Peter B said:

although if it is like turbo cars these days, the turbo is probably water cooled anyway.

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It is aircooled.

hollywood8118 said:

At 1600 rpm what speed are you seeing in flat water?
HOLLYWOOD

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Thank you, everybody, for answers.

Hollywood, I just bought the boat as of today and I have never been in flat water in it yet!!

The sea trials last week we had in a really good blow, I think the strongest in Strait of Georgia this year yet. That was a real fun, fun, fun. I was steering the boat and the surveying mechanic asked for 2,600 RPM for approx. 10 min.
The owner got apprehensive but I was glad to give it some berries.

On the way back home the ferry Nanaimo-Horseshoe Bay was struggling (one hour delay) due to reported 50 kn winds.

Meanwhile, I'm happily avoiding any turbocharged difficulties with an NA engine.

Janusz-that sounds like a helluva sea trial!

We were in protected bay so the sea was not built up, but the wind was stiff and the boat was struggling-lots of windage.

I was happy and curious to see how it behaved. I have no experience at all with small power cruisers/boats/trawlers; this is going to be my first. All I know is all sizes of sailboats and commercial ships.

Rule of thumb, run 75% load for 10 mins, for every four hours of run time. This will ensure engine temps, and turbo boost climb to designed levels, and keep everything exercised.

Janusz; said:

So, I bought myself a boat:

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Congratulations.
Boat looks good in the picture, what is it?

2600 rpm at WOT is 100rpm under propped re sunchaser's input. By "max rpm" I assume he's talking about "rated rpm". Perfect .. FYI a governor will kick in and prevent the rpm from going any higher than 2 or 300 above rated rpm. but I would'nt want a WOT rpm any higher than that. It wouldn't be harmful .. just not as ideal. I consider 50rpm under propped .. to right at rated rpm to be perfect. Hard to get perfect though as one inch pitch change will change WOT rpm 200 turns .. or so. If you were to increase pitch 1" ( for example) you would probably be over propped. Prop shops don't make 1/2" pitch changes. So you're about as good as usually can get.

How "new" is the engine? I sure would'nt want my new engine run WOT for ten min. Two or three should be sufficient IMO for sea trial unless the engine was completely "broken in". Perhaps it was good the engine was under propped. If it was over propped 100rpm it would have been much harder on the engine. It would have been slightly overloaded ... but not by much.

nemier wrote;
"Rule of thumb, run 75% load for 10 mins, for every four hours of run time."

Steve De'Antonio of PM Magazine (tech ed) said at one time that one should cruise at 75% rated power most or all of the time. Did he cave on that or?

Your rule of thumb sounds good to me though. I'm shy of that as I don't run 75% very often. I do run at 50% almost all of the time though. I almost never run less than 50%. These numbers are % of load (or max fuel burn) not % of rpm. Very very different.

manyboats said:

.............

"Tony De'Antonio of PM Magazine (tech ed) said at one time that one should cruise at 75% rated power most or all of the time." ................

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Any relation to Steve D'Antonio of Steve D'Antonio Marine Consulting, Inc. who once wrote tech articles for PM magazine (he quit writing for them in 2014)?

OOPS my bad .... indeed Steve.
Thanks for posting quickly so I can correct it .. I did.

manyboats said:

Steve De'Antonio of PM Magazine (tech ed) said at one time that one should cruise at 75% rated power most or all of the time. Did he cave on that or?

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I could be very wrong here, but it is my understanding that the newer common rail diesels don't suffer from being at less than that 75% power like the older diesels did.

The old rule of thumb on running at 75 or 80% load now and then is not necessary for the PS engine in question. It has a coolant to oil heat exchanger that keeps the oil temps high enough at light loads that even at 1500 RPM oil temperatures are 180 F. But it won't hurt anything if the boat is correctly propped.

Dave,
Read "not so much" I think ..... but don't really know for sure. As long as the lube oil gets up to 160 or above lower loading may be fine. Coolant temp means little as it's artificially held up by the thermostat. Not an indication of work being done. Now if you took out your thermostat and ran your engine at 180 degrees coolant temp ... Yup that's loaded. But running w/o a thermostat is not a good thing to do. I'm expressing my opinions but Tom (sunchaser) knows more about this so I mostly defer to him.

Hawgwash said:

Congratulations.
Boat looks good in the picture, what is it?

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Thank you.
The boat is a 1982 4o ft OA Europa.

Now, this over/under propping business is somewhat unclear to me.
The boat originally had single Lehman.
It was repowered in 2011 with Sabre Perkins M225 TI and there is 364 hrs on it. The oil was changed once (how it should be) and sample was analyzed - all OK.
When mechanic asked for 2600 rpm I was at the controls and eased the throttle very slowly until 2600 - but I do not think I pegged the lever; in other words I think it was not totally WOT but very close. I did not even think about speed over the water since everything was quite turbulent.

I will ferry my new darling from Duncan home to Garden Bay next week and hopefully will have a chance to observe all the parameters. The bottom was powerwashed and I am looking forward to fine crossing.

75% load? How would I determine that?

I am totally ignorant about marine diesels, but my seat of the pants tells me that to travel up to displacement speed I would need significantly less then 75% of max load.

We will see how it goes.
All I know that practice is frequently much different then theory and common sense is the best solution.

Hello Jansuz and congratulations on the new boat. Hopefully this will help. My boat has 3208 Turbo Caterpillars, max loaded RPM is 2800 so 75% of load is 2100 RPM.

I run my engines at 1200 - 1300 RPMs or 45% of max load which gives me about .5 kt below hull speed. Every four hours I bring the engines up to 2100 RPMs for 5-10 minutes just to clear out the turbo and ensure everything comes up to proper temperature, then back down to hull speed.

If you are not already a member take a look at boatdiesel.com, it's $25 to join and there is a wealth of information to be had.

My old sportfish had Cat 3208 Ts rated 320 hp.

I used to troll for fish hour after hour at idle to 1000rpm in gear and sometimes one engine at 1000 or less.

Followed the dock telegraph advice of 10 minutes at high rpm (200 or so under max) every 4-6 hours of trolling. The engines would belch smoke for about 2-3 minutes, clean up and be smokeless for the rest of the time.

I sold the boat (1986 boat/engines) 11 years ago with around 3700 hrs on the engines and last year the new owner called, said he had to get new props...changed then a tad in size and pitch...and the boat has never run better picking up several knots throughout the rpm range.

My guess is the engines now have 5000+ hrs on them based on that the new owner uses the boat a lot.

My point was that those turbo engines spent a lot of time fishing at idle or very low rpms with the recommended "blow out"...and seem to be surviving just fine. Just remember, these were 1986 engines (technology).

Janusz said:

It was repowered in 2011 with Sabre Perkins M225 TI and there is 364 hrs on it. The oil was changed once (how it should be) and sample was analyzed - all OK.

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Consider this only a question and the fact that the oil analysis was good indicates that things are fine but....

Even though it only has 364 hours on the engine, I would think that good practice would be for the oil to have been changed yearly. Oil, once it has been run, "deteriorates" just sitting in the engine.

Now, oil analysis seems to contradict that in this case. Is the concept of at least yearly oil changes something that I need to just get over?

dhays said:

Consider this only a question and the fact that the oil analysis was good indicates that things are fine but....

Even though it only has 364 hours on the engine, I would think that good practice would be for the oil to have been changed yearly. Oil, once it has been run, "deteriorates" just sitting in the engine.

Now, oil analysis seems to contradict that in this case. Is the concept of at least yearly oil changes something that I need to just get over?

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Reread the thread...I think the oil analysis was done after the the last oil change...when that was?

Janusz,
Find out from the manufacturer what the engine will burn in gph at rated rpm and wot. Get your own boat propped to rated rpm at wot. Then do the best you can at determining how many gph your boat burns at any given rpm. If your cruise burn is 4gph and at wot it's 8gph you are at 50% load at cruise rpm. And if your engine makes 200hp at rated rpm then w the above example you're making 100hp at cruise.

I think the above is correct. Please set me straight if not.

I believe that is a Marine Trader, right?

dkasprzak said:

Hello Jansuz and congratulations on the new boat. Hopefully this will help. My boat has 3208 Turbo Caterpillars, max loaded RPM is 2800 so 75% of load is 2100 RPM.

I run my engines at 1200 - 1300 RPMs or 45% of max load which gives me about .5 kt below hull speed. Every four hours I bring the engines up to 2100 RPMs for 5-10 minutes just to clear out the turbo and ensure everything comes up to proper temperature, then back down to hull speed.

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Load is not determined by percentage of engine RPM. On mechanical engines it is percentage of maximum fuel rate. On electronic engines it is position as a percentage of maximum fuel limit.

Many engines today have guages to measure load. However, in it's most basic form it is the horsepower used as approximated by the fuel used.

Now, it's more complex than I'm presenting here, but here is a simplified example. I have engines which at WOT use 117 gph of fuel. I'm targeting 75% load so I'm targeting 88 gph of fuel required. These are 1200 hp engines so that is my best estimate of using 900 hp. 117 gph of fuel is at 2025 RPM (which is 84% of max RPM of 2400).

I can site a small Riva for which cruising speed is rated by the manufacturer at what ends up being 87% of max RPM but only 77% of maximum fuel usage.

psneeld said:

Reread the thread...I think the oil analysis was done after the the last oil change...when that was?

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Ah yes. Thanks. I misread that.

Is that engine a non-electronically controlled model?

The engine is not electronically controlled. No computers.

The boat is Ocean Alexander -OA - not Marine Trader.

The oil analysis was done by my surveyor-mechanic 2 days ago using a Surrey lab. The oil change was approx. 1,5 yrs ago by previous owner.

He kept all the receipts, manuals, bills, ship's log etc and the whole documentation which takes a whole shelf and weighs at least 20 lbs, I am sure. That was one of the compelling reasons I bought this boat.