engine power vintage pearson boats

[Charles Bachmann]

I am  wondering  how many  atomic 4 engines  are still  ou there  in our old vintaage boats  

[Tim Tinker]

My 1979 P30, #1106, has the original atomic 4...this is my third A4, one in a Grampian, one in a Catalina so I've figured out some of the quirks, especially overheating...

[Dave Cole]

There are a lot out there still.

My 74 10M has an Atomic 4 still.   No plans to change it out.  It runs fine.   Parts are still available.  

Dave

10M #26

On Mon, Aug 11, 2025, 10:57 PM Charles Bachmann <mmyctr...@gmail.com> wrote:

I am  wondering  how many  atomic 4 engines  are still  ou there  in our old vintaage boats  

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[Guy Johnson]

Puffin has her original A4. 

10M #6

On Aug 12, 2025, at 8:44 AM, Dave Cole <dave...@gmail.com> wrote:



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[Dan Pfeiffer]

Pyxis cane with a Volvo that has gone to that great black diesel cloud in the sky.  I went electric with a 12kW kit from Thunderstruck Motors.  It is superior in every way but range.  I can motor about 25 miles at 5 kts which is more than adequate for our current use.

Dan Pfeiffer

[Al Taylor]

PO repowered 20-25 years ago with Yanmar 3GM30F. 

On Aug 12, 2025, at 9:35 AM, Dan Pfeiffer <d...@pfeiffer.net> wrote:



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[Robert Franklin]

I have more than a passing affection for the venerable and effective A4. 

When I get a little further past old age ... into the "elderly" category ... I would like to pick up an A4 just for the sport of another rebuild. This time more extensively than I boasted about in the past. Let's say reboring cylinders, new rings, stuff like that. 

I happen to have a nice carburetor in my inventory ... not sure why?

There was a time when I wanted to put one of my prior rebuilds clean, polished and nicely painted in the living room with the exhaust ducted into the chimney. 

Why not, I thought? Entertainment for the company and me too.

Anne vetoed that one.

 

Bob Franklin

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[Robert Franklin]

More A4.

Diesel needs a large capacity battery to start.

Electric needs more than the sun shining.

A4: a hand crank and hand held 12v battery.

What's not to love?

[Ed Criscuolo]

And don’t forget $5 spark plugs vs $100 fuel injectors.

@(^.^)@ Ed

Sent from my iPhone

[Jim Keszenheimer]

Ditto that with my ‘75 10m.

Wish I could figure out how to remove the exhaust bolts. It’s severely corroded on top of the water inlet loop and leaking. I just can’t put a torch on the bolts so close to gas. I’ve tried an inductance heater and lots of penetrating oil. I just don’t want to snap and have to drill them out. 

Jim

On Aug 12, 2025, at 8:44 AM, Dave Cole <dave...@gmail.com> wrote:



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[Dave Cole]

Do you have bolts or studs holding on your manifold?   Think I have studs with nuts holding the manifold one.

A hacksaw can cut off the nuts.  Cut next to the stud.  Then turn the nut to bend/break it with vise grips.   

I have used a propane torch in the engine compartment a few times.   Make sure the gas is turned off.  Remove the spark arrestor and tape the carb mouth shut.  Or tape over the spark arrester. Run the bilge blower for 5 + min to get rid of vapors which are heavier than air.  Keep it running.  Keep the torch away from the fuel lines.  

A cut off wheel in a grinder will also work.  They throw a lot of sparks so same precautions.  Pay attention to where the sparks are going.

I have soldered used gas tanks before.   Cut apart used propane cylinders, etc.  You need to be careful, but its done all the time.  Knowing how to do it is key.  Precautions are the rule.  

Dave

10M #26

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[Jim Keszenheimer]

Thanks Dave. Good advice and precautions. My local boat mechanic said he wouldn’t chance using a torch so I figured I shouldn’t even consider it. Maybe I need to ask another.

 I have bolts holding the exhaust flange to the manifold which I figured would be the best to remove. Alternatively I could remove the manifold but lots more work and I’m sure those bolts won’t budge either. 

Jim

On Aug 15, 2025, at 1:08 PM, Dave Cole <dave...@gmail.com> wrote:



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[Charles Bachmann]

My  good old atomic 4  raw watrer cooled is running very  hot  ...  the exhaust is down to a trcikle  ...

 I  have not chaged the  impeller  since  I  put in the new  pump  6 years  ago  ..maybe 7  ...

hope this does it  .  

[Peter Trunfio]

Charles,

Before launching this spring, I fired up the trusty [50 y.o.] A4. She fired right up, as always.

But no water was coming out the tail pipe.

It was pouring from the wet exhaust elbow into the bilge.

There was a quarter sized hole in the elbow...

When I removed it, it was fairly well clogged with rust.

I rebuilt the exhaust from the exhaust flange on the manifold all the way back to the waterlift muffler.

Point is, if it's not the impeller...it's probably a clogged exhaust...

PMT

Peter M. Trunfio

+1.917.640.6450 (c)

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[Jim Keszenheimer]

Peter,

How did you get the exhaust bolts free?

Jim

On Aug 15, 2025, at 8:34 PM, Peter Trunfio <peter....@gmail.com> wrote:



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[DaveL 1969 Pearson 35]

Eminently rebuild-able!

m

[Michael Denny]

A change of topic:  On my Pearson 30 I have a vintage Ronstan handwheel backstay tensioner.  Suddenly after 40 years the backstay has rotated about 90 degrees putting a twist in the wire, and I can’t understand why or how it is possible.  The picture shows the rotation, but the end of the threaded rod connecting to the stay wire appears swaged to the screw follower block that moves up and down within the tensioner cage.  This block appears unchanged and the rod end still feels flush to the bottom of it.  The handwheel itself is keyed and held on with a nut that the threaded rod and backstay attachment passes through.  The key likewise appears rotated.  The problem is how to change the rotation of the tensioner rod back to its proper alignment with the backstay’s natural position.  Other than the swage in the block, I do not see how.  Has anyone had experience with adjusters like this?

 

Thanks, Mike P30#853

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[Bob Maxwell]

You can't trust an impeller to survive much more than 3 years. Yes, some will last but many won't. When you take the old one out, it will likely be missing a number of paddles. Those paddles could be jammed in cooling passages in the engine. Until you find them and remove them, or are 100% they are gone, there is no guarantee cooling performance will improve. Sorry to be a wet blanket.

Bob

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[Dave Cole]

If your manifold is leaking or severely corroded, It probably needs to come out.

I would apply Kroil or Automatic transmission fluid mixed 50:50 with acetone and apply to the bolts on the flange.    If they don't come out after some soak time with the penetrating oil, break them off with a socket wrench.  Or cut them off with a hacksaw blade.

If you can get an impact wrench on them you will have a much better chance of getting  the bolts out.   The impacts will jar the bolts loose whereas just cranking on them will frequently break them off.  

If you have bolts holding your manifold to your engine block, heat won't help.   The threads are in the block.   Too far from the head of the bolts for a torch or heat to do any good.  Put a socket on the bolt heads and try and work them out.   Because they are buried behind the manifold into the block, there is a good chance the bolts will come right out.   If you have a small impact wrench again, your chances of removal are better.    I have a small Harbor Freight Hercules 3/8" impact that I think would fit into the space.  Perhaps you want a new tool or know someone with such a wrench? 

It sounds like your manifold may be shot.   Moyer Marine sells them.  

Dave

10M #26

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[Michael Denny]

[Peter Trunfio]

Luck?

I bought my 1974 10M eighteen years ago (Feb. 2007).

I’ve re-plumbed the entire fuel and raw water systems to the engine…as well as the electrical side (starter, alternator, electronic ignition, etc.), but I had never touched the exhaust side of the engine.

I was scared the exhaust flange bolts would be the problem…but it was surprisingly easy. Before I put a wrench to them, I was pleased to see that the SS bolt heads were still nice and “shiny.”

The top (outboard) bolt cam out easily…almost too easy.

The bottom (inboard) one fought me…but only just. I sprayed on some PB Blaster and, after a few minutes, some gentle taps with a hammer, and it too came right out…no dramas.

When I put it back together, I used some 18-8 Stainless Steel Cup-point Set screws from McMaster-Carr (3/8”-16 x 2.25” long)…and some 18-8 SS hex nuts.

My logic being…if you use bolts, it’s the end of the bolt inside the block, manifold, etc. And if that gets seized up, you’ll struggle to get it out.

BUT…if you use these set screws, then the hex nut is OUTSIDE the block, manifold, etc…so theoretically shouldn’t get “as stuck” as a bolt in the block.

Worst case scenario, the nut seizes to the set screw, and the whole thing turns out when trying to loosen the nut.

That was my thinking anyway.

I redid the entire exhaust in 316 SS Thick-wall (Schedule 80) pipe (USCG requirement for “threaded” exhaust pipe?).

The new exhaust should last longer than the rest of the boat…or at least longer than me…

Only thing I would do differently is go slightly shorter on the set screws…2.0”, if not shorter…

PMT

Peter M. Trunfio

+1.917.640.6450 (c)

On Sat, Aug 16, 2025, 9:21 AM Jim Keszenheimer <jkesze...@gmail.com> wrote:

Peter,

How did you get the exhaust bolts free?

Jim

On Aug 15, 2025, at 8:34 PM, Peter Trunfio <peter....@gmail.com> wrote:



Charles,

Before launching this spring, I fired up the trusty [50 y.o.] A4. She fired right up, as always.

But no water was coming out the tail pipe.

It was pouring from the wet exhaust elbow into the bilge.

There was a quarter sized hole in the elbow...

When I removed it, it was fairly well clogged with rust.

I rebuilt the exhaust from the exhaust flange on the manifold all the way back to the waterlift muffler.

Point is, if it's not the impeller...it's probably a clogged exhaust...

PMT

Peter M. Trunfio

+1.917.640.6450 (c)

On Fri, Aug 15, 2025, 8:25 PM Charles Bachmann <mmyctr...@gmail.com> wrote:

My  good old atomic 4  raw watrer cooled is running very  hot  ...  the exhaust is down to a trcikle  ...

 I  have not chaged the  impeller  since  I  put in the new  pump  6 years  ago  ..maybe 7  ...

hope this does it  .  

To view this discussion visit https://groups.google.com/d/msgid/pearson-boats/748054b1-50e0-44ab-9b30-120ee984b861n%40googlegroups.com.

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[Jim Keszenheimer]

Thanks Peter, yes it sounds like you got very lucky with a conscientious PO! I didn’t think about using stainless for the exhaust cuz I’ll be long gone before another one rots but makes to leave it for the next. 

Cheers

Jim

On Aug 16, 2025, at 4:22 PM, Peter Trunfio <peter....@gmail.com> wrote:



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[Jim Keszenheimer]

Thanks for the sagely advice Dave! It’s the exhaust pipe at the water loop that’s corroded through, not the manifold so I’m trying to remove the flange bolts.

Since I have bolts instead of studs and nuts, that makes sense about applying heat not working well. I got the feeling any applied heat just sucked into all the metal. 

I have not tried an impact wrench, which I do have - that’s a great idea. I was afraid it might just round the heads, but it’s worth trying at this point. I have applied PB liberally for last whole season so I may continue with more before I try again. I just fear breaking the bolts thus ending my season prematurely. Just risk adverse to losing some of my already limited sailing time. 

Some photos….

Exhaust wrapped in white fiberglass: (how many studs/bolts hold the manifold on? Looks like two studs and one bolt?)

Top exhaust flange bolt (note, very limited access to get an impact wrench on bottom bolt)

Zoom in on bottom bolt, something is quite close in line.

Top of drip loop:

On Aug 16, 2025, at 1:24 PM, Dave Cole <dave...@gmail.com> wrote:



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[Guy Johnson]

I don't fully understand how that tensioner works. I appears that turning the handwheel is causing the backstay to turn. 

Try putting a long screwdriver or other pry bar in the toggle at the end of your backstay and use it to rotate the backstay into alignment.

Something that holds the backstay stud must have failed, you mentioned a key, a swage and a cage. Maybe one of those is the problem. 

Guy

Sent from Outlook

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From: pearso...@googlegroups.com <pearso...@googlegroups.com> on behalf of Michael Denny <rega...@gmail.com>
Sent: Saturday, August 16, 2025 2:27 PM
To: pearso...@googlegroups.com <pearso...@googlegroups.com>
Subject: [pearson ] Backstay adjuster

 

On my Pearson 30 I have a vintage Ronstan handwheel backstay tensioner.  Suddenly after 40 years the backstay has rotated about 90 degrees putting a twist in the wire, and I can’t understand why or how it is possible.  The picture shows the rotation, but the end of the threaded rod connecting to the stay wire appears swaged to the screw follower block that moves up and down within the tensioner cage.  This block appears unchanged and the rod end still feels flush to the bottom of it.  The handwheel itself is keyed and held on with a nut that the threaded rod and backstay attachment passes through.  The key likewise appears rotated.  The problem is how to change the rotation of the tensioner rod back to its proper alignment with the backstay’s natural position.  Other than the swage in the block, I do not see how.  Has anyone had experience with adjusters like this?

 

Thanks, Mike P30#853

 

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[Dave Cole]

---------- Forwarded message ---------
From: Dave Cole <dave...@gmail.com>
Date: Sun, Aug 17, 2025, 11:59 AM
Subject: Re: [pearson ] engine power vintage pearson boats

To: <pearso...@googlegroups.com>

That doesnt look bad at all corrosion wise, at the manifold.   I only see two bolts holding the flange to the manifold.  A wobble extension on an impact should allow you to get to the bottom bolt.  If that doesnt work, try a short breaker bar with 6 point socket on the lower bolt.  Use a rubber mallet to tap on the breaker bar while holding the socket on the bolt head.

I bet those flange bolts will back out.  Go slow, use penetrating oil.  If it starts to bind removing the bolts, tighten, then backout, repeat, etc.

The other thing you can do is remove the fiberglass wrap and cut the up pipe with a hacksaw or reciprocating saw.  You will need to replace those pipes anyway.  

I would probably do that first, then remove the flange.  

If you do break a bolt off at the flange, you can remove the carburetor, and then the manifold with the two studs and the bolt in the rear.  

Once you get the manifold out, drilling and removing the broken bolt will be much easier.

When you put it back together, use aluminum anti seize paste on the bolts.   That will insure they will come apart easily in the future.  

Moyer has all the parts you need.  

My engine was rebuilt before I got the boat, so the injector was replaced at that time apparently.  The injector I have is cast iron, which should outlast galvanized.  

I would use stainless for other pipes if you are in salt water.  If you're not, galvanized should last for 15+ years.

It looks like you have a copper tube with a compression fitting at your injector.  

Thats odd.  I wonder if thats original?  My injector just has a barbed fitting on it for the hose attachment.  Make sure that copper line is secure if you reuse that.  Flexing copper will crack eventually.

I dont see any cast iron injectors at the Moyer site.  You can probably make this work.  Id probably call Moyer first.

Dave

10M #26

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[Jim Keszenheimer]

Ya the corrosion may not look bad but it is leaking exhaust into the cabin wicked bad! It looks like it’s coming from the injector and flange. I did try epoxy around the loop which helped for a short while but it’s back. 

I hadn’t seen those injectors on Moyer’s site. I’d actually bought the hot section loop from him (the Catalina model) but it won’t quite fit right on the 10m and of course it’s on too late to return.  I might salvage the flange unless I can resell it.

 Thx again Dave!

On Aug 17, 2025, at 12:40 PM, Dave Cole <dave...@gmail.com> wrote:



[Robert Franklin]

DaveL

Beautiful A4 rebuild photos.  

After the disassembly, the machining has to be done by a "shop"?

Bob Franklin

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[Guy Johnson]

You could pull the manifold off of the engine. It's not that difficult. 

If you go that way it will give you a chance to check the block thickness where the manifold bolts are. 

If you have any concern about the wall thickness, Moyer sells replacement thread kits. 

While this might sound like a good reason not the remove the manifold, it's not that difficult and can prevent an untimely problem from arising. 

Guy

Puffin 10M #6

Sent from Outlook

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From: pearso...@googlegroups.com <pearso...@googlegroups.com> on behalf of Jim Keszenheimer <jkesze...@gmail.com>
Sent: Tuesday, August 12, 2025 10:31 AM
To: pearso...@googlegroups.com <pearso...@googlegroups.com>
Cc: pearso...@googlegroups.com <pearso...@googlegroups.com>

Subject: Re: [pearson ] engine power vintage pearson boats

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