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  #1   IP: 65.131.206.147
Old 02-04-2021, 11:55 AM
CesarH CesarH is offline
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Question Cylinder head transplant

Dear folks,

Cesar Hernandez here. Don't own a sailboat but my daughter do (Catalina 30 with an A-4 gas engine). Her newer model engine is in my living room being torn down. She was given an older model A-4 that was from another boat (replaced with diesel) in better shape than the one being torn down. The issue is that the new model A-4 is raw water cooled and the older A-4 was fresh water cooled, so the cylinder heads are bit different. The older A-4 engine water disposal setup is configured differently enough that it won't fit in her boat engine space so I either need to get real creative or was wondering if an exchange of cylinder heads was possible, (new engine cylinder head put on old engine engine block would work)? Any help on this issue would be helpful
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  #2   IP: 67.234.39.238
Old 02-04-2021, 01:54 PM
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Marian Claire Marian Claire is offline
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Welcome to the forum. There is a difference in early "old" model and late "new" model heads seen here. https://moyermarine.com/product-cate...rheadmanifold/ both can be used for raw or fresh water cooling.
" The older A-4 engine water disposal setup is configured differently enough that it won't fit in her boat engine space" Are you are talking about where the coolant leaves the manifold? A picture of the set up would be helpful. Some early model A-4s have a spot for the temp sensor and a housing for the Dole thermostat located there. All of that can be modified if it is causing the space issue.

Dan
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  #3   IP: 65.131.206.147
Old 02-04-2021, 07:17 PM
CesarH CesarH is offline
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Dan,

The old engine (FWC) has a disposal unit that looks like a hookah that rises about 12" above the level of the exhaust manifold and the thermostat is located on a piece of plumbing that runs across the top of the manifold. The thermostat in the brass housing has a temperature sending unit that rises about 5" above the exhaust manifold. It is this feature that is causing an issue,because a bench seat sits immediately above this area in the boat. The boat could probably accommodate 3" but not the five. I was just thinking in terms of it being easier to switch heads than go through all the rigamarole of providing a different rigging. Being new to this forum I've just attempted to attach a picture of the H2O sensor on top of the old model A-4 that we are hoping to install in my daughters boat. Hopefully that aides you in understanding my problem. If you have any suggestions regarding how I could rigamarole around my problem it would be sincerely appreciated. Thank you for giving a hoot. CH
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  #4   IP: 67.234.39.238
Old 02-04-2021, 09:01 PM
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Marian Claire Marian Claire is offline
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That is a nice looking early model. First response is to put a 90 out of the manifold and turn the whole "hookah" lateral. That looks like a Dole T-stat housing and a nipple to adapt to the temp sensor. Do you have room to do that? There are other options but that is the simplest.
Dan
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  #5   IP: 65.131.206.147
Old 02-09-2021, 02:22 PM
CesarH CesarH is offline
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Marian Claire,

Looked at the possibility you mention in your previous post, but trying to stay away from turning my daughters raw water drive into a freshwater one. That's really the gist of my question about whether a new model cylinder head would fit on an old model A-1 block? Her boat is located on Flathead Lake and there's not really a problem with salt water, which I believe is the real purpose behind a fresh water circulation system. Just thinking that the less I have to change overall, is the path of less resistance. Thanks for bearing with my questions. CH
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  #6   IP: 67.234.39.238
Old 02-09-2021, 04:25 PM
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Marian Claire Marian Claire is offline
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Does the boat have a heat exchanger? Are there two water pumps on the A-4? If not then you have some type of raw water cooled set up. The "hookah" is a bit confusing to me but no telling what the PO had set up. Maybe this will help. http://www.moyermarineforum.com/foru...hlight=cooling
I might be misunderstanding something but if you want a simple raw water cooling system than use the early head. You can even eliminate the dole T-stat and return loop, shown in the diagram, and just dump the water into the wet/dry exhaust connection. If you want a temp sensor the put a T at the exit of the manifold. One side for the sensor and the other to the wet/dry. The A-4 will most likely run on the cool side.

Dan
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  #7   IP: 67.234.39.238
Old 02-10-2021, 09:39 AM
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Marian Claire Marian Claire is offline
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Post #1. "The issue is that the new model A-4 is raw water cooled and the older A-4 was fresh water cooled, so the cylinder heads are bit different."
Just to clarify. I hope I have made it clear that the type of head or engine for that matter, early or late, is not a factor in how the engine is cooled.
It is the owners choice. RWC is the simplest. FWC requires a second pump and a heat exchanger but should extend the life of the block/head etc.
Are we clear on the terms RWC and FWC? RWC just uses the water, be it fresh, salt, brackish, polluted etc, that the boat is sitting in and pumps it thru the block/head/manifold and wet/dry exhaust connection. FWC has two separate loops. The block/head/manifold/heat exchanger has antifreeze, car antifreeze, pumped thru it in a closed loop. The antifreeze is cooled when it passes thru the HX. The HX and wet/dry connection are cooled by a raw water loop.
Based on what you have posted I would install the early model and set up RWC as the diagram shows or without the Dole T-stat housing and return line. We can go over the pros and cons of each if you go this way.
More pictures of the both A-4s and the engine compartment in the boat would help use see anything that might cause issues. Such as direct drive vs 2 to 1 reduction gear.

Post #1. "or was wondering if an exchange of cylinder heads was possible, (new engine cylinder head put on old engine engine block would work)?"
I looked in to this several years ago when I was trying to create a spare head for my early A-4. I know I had to fabricate a cover for the late T-stat housing and get a plug for the unused temp sensor opening. It has been 12+- years age but I believe the bolt holes and water passages lined up. I believe the late head had two holes near the exit from the head that I had to drill out to match the early head. The cross over tube would most likely need to be replaced with fittings and a hose.
I will try a confirm this. But there is really no need to go down that road unless it is the only option.

Dan
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