Perkins T6.354 Best Practice

What are the best upgrades for the Perkins T6.354, or is there a page dedicated to this topic already? With over 1M motors produced I'm assuming there's a lot of knowledge about keeping these engines in top shape, optimizing reliability, efficiency, performance and maintainability.

For example, I have seen the following:

• Spin-on fuel filter at fuel pump
• Upgrade head gasket
• Single-piece wet elbow with EGT
• Upgrade turbo to H1C
• Secondary electric lifter fuel pump as primary is a point of failure
• Put exhaust manifold in fresh water circuit

I am very interested in all the different modifications that have been done and how they affect the motor.

Thanks,
Robert Ryan

I owned a 78 Mainship 1 that had this engine as oem. I ran that engine for 9 years then repowered because I could not get parts.
I also worked on several, and helped many others with their Mainship engines as I ran the NE group for many years.
Some of those you mentioned I have heard of. They are not all "upgrades".
The spin on filter makes changing more convenient/less messy, but I kept mine as is.
Never heard of an upgraded head gasket. Never knew anyone who blew theirs and had to change.
Single piece wet elbow was oem as far as I know. It was designed properly to let water always drain out.
The diaphragm lift pumps are not prone to failure like some of the others, at least not the oem pumps. Perhaps aftermarket pumps fail, but they are cheap and easy to replace. I personally wouldn't bother since they offer no performance enhancement.
IF the oem turbocharger needs replacing, a Holset H1C would fit (with air plumbing mods) but is only a very slight "upgrade". You would not notice any performance increase unless you tweaked the injection pump to get more fuel. The H1C flows a little more air
so perhaps it could handle more fuel.
Fresh water cooling the exhaust manifold would be the best upgrade of all you mentioned. They have a short life in salt water and they are extremely expensive to replace. I never did mine, didn't know or think about the mod until after I repowered.

If you want the biggest performance increase in your 78 Mainship, fair the keel ahead of the prop. I did that (ahead of my planned repower) and gained 250 engine rpm just on that alone. I was able to add 2 inches of pitch to the prop after the fairing job. See picture below
Oh...and get the injection pump rebuilt. Doing that was huge improvement in my boat. Made it run stronger (meaning it got to rpm quicker) and smoother.
Have fun.

Greetings,
Mr. Rp. I've never had a Perkins but welcome aboard anyway.

JLeonard,
Thanks for tips, I actually bookmarked your keel fairing post a while ago and have a separate thread on the Yahoo Mainship list for hull modifications. One of the PO's of my boat installed wedges however I believe they were incorrectly installed under the transom. This weekend I'm diving to check out the prop and condition of the keel. I wonder if there's an underwater glue that would hold a fairing - I'd rather not haul out unless also painting.

Did you ever consider increasing the rudder size? I have poor handling in seas that are anywhere aft of abeam. At 7 knots and two foot cornering seas I'm getting a workout with the knob on my wheel (that sounds profane, sorry).

Wait and do the fairing right when you are out of the water.
I considered adding to the rudder, but was advised against it by the folks at my marina. I never had any trouble manoevering, just wanted better tracking.
I also installed 12 x 42 trim tabs. That made a huge difference in low speed handling. I could be "on plane" at 8 knots. Helped reduce rocking at anchor as well.

I'm liking the trim tabs idea. Which vendor did you go with, and how much did that cost? I'm contemplating an extension of two feet to increase planning surface.

jleonard said:

I owned a 78 Mainship 1 that had this engine as oem. I ran that engine for 9 years then repowered because I could not get parts.

Click to expand...

Are all the 34 Mainship and Mainship IIs powered with Perkins? All T6.354?

(An acquaintance says he's looking at a Mainship II with diesel, but he didn't know what diesel. Our Mainship III had a DD 8.2T...)

Is the Perkins a 200-hp turbocharged engine?

Are parts really hard to get?

Any significant problem areas with that engine?

-Chris

Chris, they range in hp depending on turbo and exactly which version of the 6.354 is in there.

We've got twin t6.354.4m s in our 40' mainship but we've heard of the same model stock with gassers.

Big things to look for are corrosion in anything where the seawater flows through. Most of these parts, coolers, heat exchangers, are weird metals and require bonding or their own zincs. Oem parts are getting more and more difficult.

jleonard said:

I owned a 78 Mainship 1 that had this engine as oem. I ran that engine for 9 years then repowered because I could not get parts.

Click to expand...

What did you choose to repower with?

"Are all the 34 Mainship and Mainship IIs powered with Perkins? All T6.354?"


My 1978 Mainship 34 was a Perkins T6 - 354 at 165 hp and all of the ones I had seen up here on the East coast were the same - but there could be other versions I am not aware of although the power increases on that engine typically came much later on in years.


"Is the Perkins a 200-hp turbocharged engine? "
Mine was a 165 Turbocharged engine - I believe the turbo was a 'switzer'.


"Are parts really hard to get?"
As mentioned above the exhaust manifold for mine had to come form England and was expensive as boat parts go - most other things were not so bad as aftermarket or common parts were still available.


"Any significant problem areas with that engine?"
Exhaust, turbo rebuild, heat exchanger, and the rotary fuel pump that liked to 'hunt' until it was refitted with "O" rings that were unaffected by low sulfer fuels.


FWIW - My engine had a "U" in the code indicating a 'reverse' rotation engine.

"What did you choose to repower with?"


There were two Mainship 34's that we saw up here over the years at the town docks that were repowered - both had Yanmar's which I believe were at about 240 Hp.

I repowered with a Cummins 6bta at 270 hp. It made a whole new boat imo. I could cruise at 15.5 knots (didn't do that very often) and could get 18.5 at wot.

Re trim tab, I installed bennett hydraulic tabs.

Thanks, all, very useful.


-Chris

Is 2600 RPMs at WOT too fast for a 1977 T6.354? This is underway with normal load.

Thanks,
Robert

R_p_ryan said:

Is 2600 RPMs at WOT too fast for a 1977 T6.354? This is underway with normal load.

Thanks,
Robert

Click to expand...

It won't hurt anything, but 2450 at WOT is the spec.
You should be able to add 1 inch of pitch if you choose and that will lower your WOT rpm and give you a "little" more speed. Or add some cup to the prop instead.
Or leave it and let the engine "loaf" a little. Then when you are at "vacation load" you won't be over propped.

The age of the engine has nothing to do w it if it's in good condition.

As long as the rated rpm for full continious load isn't exceeded all should be well.

Fifty to 100rpm over rated is ideal for WOT in my opinion. Ask your prop man if a 1" pitch increase will reduce rpm more than 200. If so I'd run it as is. If not give it an inch more pitch. I personally don't think cupping props on a trawler is good or in anyway beneficial.

Jay,
Sorry to disagree w you on the cupping however I really like your expression "vacation load". I think I know what you mean but could you expand on that?

Jleonard, I'm also going to add the keel fairing you describe, so in theory should I go up two inches? I really wish I had a variable pitch prop.

And thanks for clarifying the WOT max rpm.

Vacation load is when you have 6 cases of beer on board, 2 coolers full of ice beer & steaks, 6 gallons of extra "dinghy gas", yada yada.
I remember our 1st 3 week vaca after the repower. WOT went from 2630 to barely 2500. Lol
And the cupping paid off for me because it kept my idle speed down after the repower yet gave me the speed at cruise rpm. Without the cupping I would have had to buy a new prop

This thread interests me as we are looking at a boat powered by a single 1999 6.3533M Range 4 with 3900 hours on it. It's a naturally aspirated 135hp, with 2008 Twindisc MG5011MC gearbox, and 23LH21 3-blade prop on a 1.5" SS shaft) It's a 19 ton full displacement boat, so the 7 kt speed is not a concern/issue... but reliability and cost of ownership are.

I know absolutely nothing right now about Perkins engines , though if we proceed with the purchase, I will definitely have to learn. The pics below show the engine (facing fwd) and 2 shots of the running gear (fresh bottom paint in April 2015). We have not been on the boat yet, so I haven't been able to get up close and personal with conditions.

Assuming visuals, surveys and oil samples come out ok, is there anything in particular I should be aware of on this power plant? Any idea how much a rebuild would cost? A SWAG is fine. If a repower were necessary, ideas for possible replacement are welcome.

Trans Atlantic Diesels can rebuild it for you. Very roughly- $10-15,000.

If you want to repower it a factory remanned Cummins 6BT 210 hp would be a good choice. More hp than you need, but you can run it slow. Essentially a new engine for about $20,000 +/-. Should be slightly more fuel efficient.

But that engine should last a lot longer than 3,900 hours if maintained and run right. Sure its a 1999 engine. Many boat builders switched to the above Cummins by then.

David

Thanks David. This is precisely the kind of information I was looking for... particularly the bit about engine life. 3,900 hours seems like a lot, until you break it down by average hours/year (~244). This tells me that the boat was used, and not just sitting in a marina someplace. One can only hope (at this time) that it was properly operated and maintained.

Any thoughts (pro or con) on the running gear setup?

We're hoping to get down to take a look at the boat today.

djmarchand said:

Trans Atlantic Diesels can rebuild it for you. Very roughly- $10-15,000.

If you want to repower it a factory remanned Cummins 6BT 210 hp would be a good choice. More hp than you need, but you can run it slow. Essentially a new engine for about $20,000 +/-. Should be slightly more fuel efficient.

But that engine should last a lot longer than 3,900 hours if maintained and run right. Sure its a 1999 engine. Many boat builders switched to the above Cummins by then.

David

Click to expand...

I have the 6.354 Range 4 135 hp with 4400 hrs. Starts easy, runs smooth, low oil consumption, very little smoke and is easy on fuel. So far its been a pleasure to own.

we've got two. and have seen serious corrosion issues in anything that has seawater running through it. check the coolers, especially where they bolt together, for signs of corrosion.

my experiences with TAD have been mixed - the prices definitely seem to be on the rise but they are a good start in your search of original parts. mrcool.com is a much more economical option if you don't care that the coolers look a little different.

they do still run strong though....even being from 1979

Before having a boat yard do any rebuild , go to Boats and Harbors and find out what a commercial rebuild would cost ,and esp with common engines like a pick up truck motor what an entire short block, or full crate engine would cost.

You might be shocked to learn new is 1/2- 1/3 or less than rebuilt locally.

More interesting to pay for the paper version , tho its on line.

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My Prairie 29 has a T6-3544M marine engine, "Range-4". The service manual I have says that engine carries several different ratings, even though they are all the same engine. The "Pleasure Craft-high" rating is 250 BHP at 2800 rpm. The "Pleasure Craft and light commercial duty" rating is 220 BHP t 2600 rpm, or 185 BHP at 2400 rpm. There are other ratings, but those are the most commonly encountered ones.

My boat is over-propped so it can't even hit 2400 rpm. But, I have the advantage of cruising at low rpm, so there's lower noise and fuel burn.

The distributor for parts for the Midwest and Northeast is Power Great Lakes. They have a very helpful parts department and seem to be able to access everything needed for popular engines like the 6-354. Their phone number for the direct line to the parts department is 888-331-5769.

Personally, I would see no problem for the foreseeable future in supporting a Perkins marine engine.

Good Luck!

J.S.

"My boat is over-propped so it can't even hit 2400 rpm. But, I have the advantage of cruising at low rpm, so there's lower noise and fuel burn."


It is rare that being overpropped is a good thing. The fuel burn on a diesel will not be better with too much prop and often will be worse. The boat speed will demand a specific amount of hp which will equate to a fuel burn equivalent but if you try and pull too much out at lower rpms a number of poor engine issues will begin. If you have a fuel curve for that engine you may see that it is even more efficient at higher rpms (hp vs fuel weight).


Hope this helps

Well, Smitty you're entitled to your opinion. For a given power output, being so far below the engine's rating, the lower the rpm the better. Rise 'n Shine is using something like 25 hp to move at 7.5 knots. If I'm turning 1400 rpm it's using less fuel than if it's turning 1800 rpm delivering the same power. It's running at a higher percentage output than if it were matched to a propeller that allowed full rpm.

Since we're talking about something in the range of 10-20% of full power here, the lower the rpm the lower the fuel consumption, no exceptions. Yes, the BSFC (weight of fuel per BHP) is better at higher rpm, but that's running at full output for each rpm point. We're talking a very different case here.

More important than fuel burn, it's also more pleasant to the Commodore from the noise, and her opinion carries more weight than fuel consumption.

Onward!

J.S.

"the lower the rpm the lower the fuel consumption,"

When you set the throttle for a specific rpm you are commanding the engines governor to maintain that rpm. The governor will actively add or detract fuel to maintain that rpm despite the changing load as best it can. The function of fuel burned on a diesel is really a function of load. Diesels also really love air and turbulence to get the highest efficiencies so the more air in the combustion chamber the more efficient they tend to be. That coupled with the engine designed for higher hp per fuel weight utilized favor being on or below the recommended prop curve.
Engines with turbo's and intercoolers will see the engine run better in that range and have fewer low power demand engine buildup on or below the curve. I did have a fuel monitor on my Perkins 6-354 but it was a longer while back.
On the 34 Mainship that had the Perkins we added a decent amount of noise shielding which made the engine itself very quiet right up to 2,200 rpms + for not much money invested - just a little time mostly.


Hope this helps

Thanks, Smitty, but that's not the point in this particular case.

The power delivered by the engine (and the fuel regulated by the governor to do so) is only that which the propeller delivers to the water. Since Rise 'n Shine only requires roughly 25 BHP to move at 7.5 knots, doing so with an "over propped" screw at 1400 rpm inevitably uses less fuel compared with the same 25 BHP delivery with (what some folks call) "correct" propeller at 1800 rpm.

Ya can't change the physics.

You're in Northport - what state is that?

J.S.

Northport is in New York on Long island sounds north shore.


"Since Rise 'n Shine only requires roughly 25 BHP to move at 7.5 knots, doing so with an "over propped" screw at 1400 rpm inevitably uses less fuel compared with the same 25 BHP delivery with (what some folks call) "correct" propeller at 1800 rpm."

We really do not agree on this topic at all - perhaps if 1,400 rpms is a good solution for the fuel use and noise you could prop it to get the 25 hp at say 800 rpms and the fuel would drop to a much lower use and the noise might be so much less.


It is your boat and your engine so each must do what they think is correct.