Major Perkins Maintenance, Classic 34' Mainship, Perkins T6.354

[Gdavid]

I figured I would share my current project. I am going into my 5th year of owning this boat and it has carried low oil pressure the entire time I owned it. Just within specs but far below what the last Perkins in my family carried. It makes about 35 when at cruise speed when the oil is cold but slowly drops to around 30 over a longer cruise and is only making about 15-20 at idle with a warm engine. I suspected fuel dilution, but I have changed the lift pump and the injection pump was rebuild about 6 seasons ago. Also, the fuel pressure doesn't perform any better immediately after an oil change.

I bought the boat at the height of covid after several other boats fell through and I knew these motors are not too expensive to rebuild, so I looked past this wart and a few others. Otherwise, the motor has performed fine, not producing any problems, starts smoothly and doesn't smoke excessively but I'm just not comfortable with this oil pressure. I'm finally doing something about it. Pulling the engine, going to inspect the bearings, change the main and crank bearings, change the oil pump and shoot for some improvement. Hopefully the crank is okay but I will have it machined if necessary.

I will take the opportunity to paint the engine bay while it is out and re-gasket the bottom end, replace the front and rear seals, scrub it up and paint it.

 

[rgano]

So, you must have everything else in the boat in A-! status?

 

[Gdavid]

So, you must have everything else in the boat in A-! status?

Not really. The side decks need to be re-cored as well but I'm going to dig into that when it's warmer. Every year the boat gets a major project to keep it going.

 

[Jeff F]

Heh. I have an almost identical stand that I built to haul the motor in my 34. Is it out?

Good luck. I think I would have lived with that oil pressure, but appreciate your willingness to take these projects on!

Photos from 2016. Brings back memories!

 

[Gdavid]

Heh. I have an almost identical stand that I built to haul the motor in my 34. Is it out?

Good luck. I think I would have lived with that oil pressure, but appreciate your willingness to take these projects on!

No, I got a late start today and am trying to pace myself, today's goal was to get the gantry in place and make my game plan. Tomorrow I will finish disconnecting everything and lift her on up. I am going to crib it up in the salon and work on it there, no need to pull it off the boat.

 

[rgano]

Good deal. Admire your DIYness. Somebody will inherit a NICE boat someday.

 

[Gdavid]

Good deal. Admire your DIYness. Somebody will inherit a NICE boat someday.

I appreciate the encouragement, I have been getting a lot of use out of the boat but hoping to start making some longer trips with it and would like to increase my level of confidence in this old motor. I also want to keep it up well enough that it would be relatively straightforward to sell. It is a cheap old boat but I want to safe and reliable for my own enjoyment or sound enough to pass a survey with decent marks, no small feat for an old and inexpensively constructed production boat. Fortunately there are still a few people around that appreciate these sensible old mainships. People usually recall their old 34s fondly.

Also, I am on the younger side of most trawler owners, so I hope to hold onto it for quite a while but never know what the future may bring. I may get sick of paying marina fees and chose to sell it or decide to upgrade. As long as I remember not to rush, it is a great old boat.

 

[rgano]

Having babied along a 1972 wooden trawler for 29 years, I get it, totally.

 

[boomerang]

I admire your determination and it will certainly make it a nicer boat after the engine has been freshened up and the engine room cleaned and painted.
Have you determined that the salon flooring is sturdy enough for the weight of the A-frame engine hoist and engine? Ours had only a few flimsy supports screwed to the stringers and the outboard sides of the floor were just tabbed to the hull in a couple of places. It was strong enough to act as a floor but there's no way I would've expected it to support the weight of the Perkins.

 

[Jeff F]

Make sure the salon floor is well enough supported to bear the weight of the motor. Speaking from experience

Those boats are worth keeping in good shape. I sold mine to a guy who did a complete restoration on it*. There will always be a market.

* including fixing a partially collapsed salon floor

 

[Gdavid]

Make sure the salon floor is well enough supported to bear the weight of the motor. Speaking from experience

Those boats are worth keeping in good shape. I sold mine to a guy who did a complete restoration on it*. There will always be a market.

* including fixing a partially collapsed salon floor

Great points. I have temporary supports from the stringers up to the A-frame. I plan to add more supports on either side where I will be resting the engine but haven't done that yet. The salon deck is not very well supported at all.

 

[Gdavid]

Make sure the salon floor is well enough supported to bear the weight of the motor. Speaking from experience

Those boats are worth keeping in good shape. I sold mine to a guy who did a complete restoration on it*. There will always be a market.

* including fixing a partially collapsed salon floor

Why did you have to pull yours? I recall Shawn pulling his and having TAD go through it.

 

[Jeff F]

I killed two Cummins engines, and actually did two swaps a year apart. Better not to go there... Boat had a rebuilt 6bta when I sold it. Nice engine for that boat.

 

[Gdavid]

I killed two Cummins engines, and actually did two swaps a year apart. Better not to go there... Boat had a rebuilt 6bta when I sold it. Nice engine for that boat.

I am keeping my eye out for one. I figure as soon as I get the Perkins dialed in perfectly, a 315 or 330 6BTA will pop up for a bargain and I will jump on it. The option to run 14-16 knots would be nice but I would have to re-shaft, re-prop and replace my transmission too. A velvet drive could support a 210 Cummins but mine is contra rotation and wouldn't work anyway, even for a lower output engine.

 

[Jeff F]

The option to run 14-16 knots would be nice but I would have to re-shaft, re-prop and replace my transmission too. A velvet drive could support a 210 Cummins but mine is contra rotation and wouldn't work anyway, even for a lower output engine.

PO of my old boat went through that repowering from Perkins to Cummins. He told me that in hindsight he should have left the Perkins in place. When I got it the hard part of the conversion had been done.

 

[boomerang]

Why did you have to pull yours? I recall Shawn pulling his and having TAD go through it.

I had planned on TAD doing mine but when I was ready, they told me they were too busy. Luckily, I found another mechanic with the experience to get me going.
The yard I used had a hydraulic crane that ,after I removed the bulkhead glass door and windows,did all of the disconnecting of shafts,wires,hoses, etc, it literally took less than 30 minutes to remove. That worked out really well for me ,being able to work on the engine on the ground and not having to work around it in the salon.

 

[Gdavid]

I had planned on TAD doing mine but when I was ready, they told me they were too busy. Luckily, I found another mechanic with the experience to get me going.
The yard I used had a hydraulic crane that ,after I removed the bulkhead glass door and windows,did all of the disconnecting of shafts,wires,hoses, etc, it literally took less than 30 minutes to remove. That worked out really well for me ,being able to work on the engine on the ground and not having to work around it in the salon.

Somehow I forgot that, but should be no surprise to me, I misplaced my tape measure at least 5 times today.

 

[Gdavid]

No pictures to share yet, but I did get the motor up to salon deck level, removed the oil pan and blocked it. I had to add supports to the salon deck for both the gantry and the resting place of the engine. The CG of the boat is notably higher, the worst effect was when someone moved around the boat while the motor was suspended. My shoulders are sore from removing the motor mount nuts but everything came apart pretty well.

I was fortunate to have the help of my father all weekend. He remains the best mechanic I know and was right there in the bowels of the old boat taking her apart as at 78. I also had a friend help out and keep up with securing slack in the safety chains as it came up (and even brought beer). So while a intense job, it was a really enjoyable weekend.

I am looking forward to getting this oil pressure improved, the motor resealed and painted up, clean up some wiring and clean and paint the bilge area.

 

[CharlieO.]

No pictures to share yet, but I did get the motor up to salon deck level, removed the oil pan and blocked it. I had to add supports to the salon deck for both the gantry and the resting place of the engine. The CG of the boat is notably higher, the worst effect was when someone moved around the boat while the motor was suspended. My shoulders are sore from removing the motor mount nuts but everything came apart pretty well.

I was fortunate to have the help of my father all weekend. He remains the best mechanic I know and was right there in the bowels of the old boat taking her apart as at 78. I also had a friend help out and keep up with securing slack in the safety chains as it came up (and even brought beer). So while a intense job, it was a really enjoyable weekend.

I am looking forward to getting this oil pressure improved, the motor resealed and painted up, clean up some wiring and clean and paint the bilge area.

Good on you, I'd love to raise my engine up to do some painting of the bilge and the engine and replace the motor mounts and realign everything, that may be next year's project if we decide to keep our boat and stay on the east coast.

 

[High Wire]

This question might be a little late but here goes. Did you confirm the oil pressure with a known good mechanical pressure gauge? Sometimes the pressure senders go bad and read low or the wiring harness adds resistance and effects the gauge readings. The engine could be perfectly good. Also what weight oil are you using? That can effect oil pressure too.
Another thought... When I asked my mechanic about how to do the bearing job, he said he did it before by disconnecting the rear engine mounts plus transmission and tilting the engine forward on the front mounts to gain access to the oil pan. Depends on room in front. Everything can come out the bottom unless you are doing the sleeves too in that case take the head off first.

 

[Gdavid]

This question might be a little late but here goes. Did you confirm the oil pressure with a known good mechanical pressure gauge? Sometimes the pressure senders go bad and read low or the wiring harness adds resistance and affects the gauge readings. The engine could be perfectly good. Also what weight oil are you using? That can affect oil pressure too.

Yes, I did install a mechanic guage and unfortunately it was consistent with the gauges on the dash. It did read slightly higher but that is the source for all of the pressures mentioned earlier.

 

[Gdavid]

This question might be a little late but here goes. Did you confirm the oil pressure with a known good mechanical pressure gauge? Sometimes the pressure senders go bad and read low or the wiring harness adds resistance and effects the gauge readings. The engine could be perfectly good. Also what weight oil are you using? That can effect oil pressure too.
Another thought... When I asked my mechanic about how to do the bearing job, he said he did it before by disconnecting the rear engine mounts plus transmission and tilting the engine forward on the front mounts to gain access to the oil pan. Depends on room in front. Everything can come out the bottom unless you are doing the sleeves too in that case take the head off first.

That is an interesting approach, tilting the engine forward, the mounts on the engine would allow it if I backed off on a couple of set screws but in my case there is a bulkhead forward that would prevent the motor going that far up

On the old Mainships, the engine sits as low as possible such that the oil dump is in a hollow keel sump. It is pretty difficult to reach down into that area but while the engine is out, I will take the opportunity to clean up, paint and clean up the wiring in the engine compartment.

 

[High Wire]

That is an interesting approach, tilting the engine forward, the mounts on the engine would allow it if I backed off on a couple of set screws but in my case there is a bulkhead forward that would prevent the motor going that far up

On the old Mainships, the engine sits as low as possible such that the oil dump is in a hollow keel sump. It is pretty difficult to reach down into that area but while the engine is out, I will take the opportunity to clean up, paint and clean up the wiring in the engine compartment.

Good job! Post a few pictures when you can.

 

[Gdavid]

I have read conflicting information regarding the location of a pressure relief valve. I see what appears to be on in the crankcase connected to the oil pump but not integrated into the pump itself. That or contamination inside of it may very well be the source of my poor pressure.

 

[High Wire]

I have read conflicting information regarding the location of a pressure relief valve. I see what appears to be on in the crankcase connected to the oil pump but not integrated into the pump itself. That or contamination inside of it may very well be the source of my poor pressure.

TAD should be able to tell you that with the engine serial number.

 

[Brooksie]

I raised my HT6.354 in my lobsterboat a few years ago in part b/c of similar low oil pressure. I pressure checked the relief valve and found it relieved at 50 I turned it to 55. I checked the main and rod bearings with Plastigage and found them all within spec. I found the scavenge pump (only on H models) needed a new drive gear which would have no effect on oil pressure. I replaced the oil pump with a new OEM pump although it was within spec. I replaced the immersed, in pan, oil cooler (also only on H model) with an external cooler. Then put everything back w/ new seals. gaskets, studs, nuts & bolts.
The only thing I really found, that could impact the oil pressure, were the 2 Orings between the oil pump and the relief valve and the oil pump and the delivery casting. They were hard and cracked, but no pieces missing. These I replaced with modern Viton Orings.
After, I did have slightly better oil pressure probably from a combination of things but still never above 40 after warmup.
You don't mention what oil you are using but these engines were designed for what was called CD series 3 oil not modern low zinc, fuel saving or synthetic oils.

 

[Gdavid]

I raised my HT6.354 in my lobsterboat a few years ago in part b/c of similar low oil pressure. I pressure checked the relief valve and found it relieved at 50 I turned it to 55. I checked the main and rod bearings with Plastigage and found them all within spec. I found the scavenge pump (only on H models) needed a new drive gear which would have no effect on oil pressure. I replaced the oil pump with a new OEM pump although it was within spec. I replaced the immersed, in pan, oil cooler (also only on H model) with an external cooler. Then put everything back w/ new seals. gaskets, studs, nuts & bolts.
The only thing I really found, that could impact the oil pressure, were the 2 Orings between the oil pump and the relief valve and the oil pump and the delivery casting. They were hard and cracked, but no pieces missing. These I replaced with modern Viton Orings.
After, I did have slightly better oil pressure probably from a combination of things but still never above 40 after warmup.
You don't mention what oil you are using but these engines were designed for what was called CD series 3 oil not modern low zinc, fuel saving or synthetic oils.

Thank you for sharing, that is great information to know. On the vertical engines, there is a flat gasket between the oil pump and the pickup tube and an o-ring making the seal to the relief valve. I have removed the pickup tube but not taken the oil pump and relief valve out yet. It would make a lot of sense for this to be as simple as a hardened o-ring.

I have been running 15w40 in the engine. I tried 20w50 but it didn't improve the pressure so I went back to 15w40.

 

[Gdavid]

Some pics, I removed the pressure relief valve, done have the oil pump out yet.

 

[Gdavid]

I removed the connecting rod bearing for cylinder #6. There was one minor scrape through the lower shell. The upper bearing shell, which takes the brunt of the piston thrust had minor wear but not through the bearings material, no copper exposed. This is the bearing that should have the most wear. The part numbers on the bearing halves indicate they are standard size. Crank journal looked good but I have not measured for oblong shape yet, I doubt the crank will need any work. I also removed the oil pump and disassembled it. It is held in place in an odd fashion in my experience. A set screw from the port side of the block is what holds the pump up. The set screws engages a pronounced recess in the oil pump and there is a lock but that secures the set screws in place. No smoking gun yet.

 

[Gdavid]

This is a longshot, but I am hoping there is a Perkins expert on there. Does anyone know if anything should bolt up to the opening circled in red in the following picture? The engine pictured is not mine, it is just a picture I was able to find on the web showing the crankcase. This opening appears to connect to the oil gallery on the start board side of the engine. It looks like in some configurations (like the H or something) the oil pump would feed to it via a crossover tube or something. Directly above it on the block is the where the oil feed for the turbo is fed. I didn't take pictures of mine or have a chance to test blowing air though the turbo feed to confirm it connects to the oil gallery but is certainly appears to. This being open would cause low oil pressure but I would expect it would have virtually no oil pressure with an opening this big. This is a contra-rotation model.

I will probably end up calling TAD, I did order my new oil pump from them so I think they would offer some advice. Looks like I should block it off. I see no block off plate for his anywhere in the parts manual.