How to Switch to Antifreeze Cooled Engine

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Got it. Any one know what the compression should be on a 350?
Different gauges will show a different reading on the same cylinder, but given the gauge is 'reasonably accurate', about 140psi. You also need to see that no cylinder varies by more than 10% from the others.

Chris.......
 

Lou C

Supreme Mariner
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Nov 10, 2002
Messages
12,677
two euphemisms about boat buying:
"I was told"
"I recently acquired"
both can get you into a lot of trouble!
A boat that age, can have so much wrong with it, that if you don't have someone who is familiar with wood/fiberglass composite construction you might be making a big mistake. The mechanical issues are almost always easier to correct than wood rot/fiberglass problems.
 

Scott06

Admiral
Joined
Apr 20, 2014
Messages
6,440
Believe it or not, the motor is the 'cheapest' part of the entire boat. Is all the other stuff that can and usually will make it a money pit.
Yep. The guy who bought my old boat didn't even ask me to turn it on or water test it....he had a similar boat with identical (3.0) drive train but rotted floor and roached interior. He said he was paying me ($3400 for a 25 yr old boat) less than it would cost him to redo his boat...he figured worst case he would swap engines.
 

76SeaRay

Lieutenant Junior Grade
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Aug 24, 2017
Messages
1,071
Based upon my experience, most 350's in good condition run from 125lbs to 155lbs. Depends upon the engine and its age. High end is usually on fresh builds. They should all be pretty close to the same compression. If one or two are really low, that would indicate something going bad. On the flip side if you have one that is really high compared to the others then that could indicate a problem occurring as well. Post your compression readings by cylinder number.

Just realized that achris already answered the question.
 

scatgo

Petty Officer 1st Class
Joined
Jul 13, 2014
Messages
370
I would like to make sure the engine was properly winterized. If I pull the coolant drain plug and antifreez comee out i am going to give that a ok.
 

Lou C

Supreme Mariner
Joined
Nov 10, 2002
Messages
12,677
I would like to make sure the engine was properly winterized. If I pull the coolant drain plug and antifreez comee out i am going to give that a ok.
while good boats are hard to find due to market etc, you'd be a LOT better off, waiting till you can water test any boat you might want to buy. What you're doing is risky, even if the boat is very low priced.
 

Rick Stephens

Admiral
Joined
Aug 13, 2013
Messages
6,118
I would like to make sure the engine was properly winterized. If I pull the coolant drain plug and antifreez comee out i am going to give that a ok.
Measuring quality of winterizing by whether there is any antifreeze in the motor can be meaningless. Depends on if the motor was properly winterized as to whether the antifreeze is actually in all the proper locations. Most people do not know how to make sure antifreeze actually gets into the motor and end up putting most all of it out the exhaust.

I'm a fan of winterizing by getting all the water out, and not using antifreeze. I also do this as a regular part of late or early season boating in the Rockies. Never be able to boat if I used antifreeze every time a cold night was upon me.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
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49,574
I would like to make sure the engine was properly winterized. If I pull the coolant drain plug and antifreez comee out i am going to give that a ok.
if it was properly winterized, there would be air in the water passages.

that doesnt tell you anything of the condition of the motor/drive/stringers/transom/etc.
 

Reserector_

Chief Petty Officer" & 2021 Splash of the Year Win
Joined
Oct 15, 2019
Messages
607
Be sure to test the radio. It might only tune it music from the 80s.

I'd be more concerned about the wood structure; floor, stringers, transom. Everything else bolts in.
BTW, I think we've strayed off topic.
 
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scatgo

Petty Officer 1st Class
Joined
Jul 13, 2014
Messages
370
Be sure to test the radio. It might only tune it music from the 80s.

I'd be more concerned about the wood structure; floor, stringers, transom. Everything else bolts in.
BTW, I think we've strayed off topic.
Or disco. LOL Yea way off topic but still good info. The only way I can think of " looking" at any wood that would be covered in fiberglass would be to use a IR camera. The only problem with that is I have know idea what I would be looking for with a IR camera.
 

Rick Stephens

Admiral
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Aug 13, 2013
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Or disco. LOL Yea way off topic but still good info. The only way I can think of " looking" at any wood that would be covered in fiberglass would be to use a IR camera. The only problem with that is I have know idea what I would be looking for with a IR camera.
Typically we take a drill and drill in from the inside, looking at the shavings that come out. Then fill the hole with 5200. One can also pull a motor mount bolt and see if the wood it is screwed into is mush or not. Typical places for first rot is lower part of transom, we drill in as close to bottom of keyhole bolts as we can. Next is motor mount and stringers. Also check the floor for soft spots. Old manufacturing techniques did not seal things up very well. Those of us who have redone floor, stringers and transom tend to make sure they are fully sealed.
 

scatgo

Petty Officer 1st Class
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Jul 13, 2014
Messages
370
Typically we take a drill and drill in from the inside, looking at the shavings that come out. Then fill the hole with 5200. One can also pull a motor mount bolt and see if the wood it is screwed into is mush or not. Typical places for first rot is lower part of transom, we drill in as close to bottom of keyhole bolts as we can. Next is motor mount and stringers. Also check the floor for soft spots. Old manufacturing techniques did not seal things up very well. Those of us who have redone floor, stringers and transom tend to make sure they are fully sealed.
Good info. Thanks. I did remove a transducer mount off the bottom of the transom to get a clue. The screws were large enough in diameter where I could see the wood was solid. I know what a keyhole is but keyhole bolt?
 
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scatgo

Petty Officer 1st Class
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Jul 13, 2014
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370
Looking forward to seeing the pictures. My boat is similar, 81 Searay with a Mercruiser and SBC.
I didnt think to take any pics of the inside but wait until you see that. It has a kitchen, two "bedrooms" and a bathroom. O yea AC and heat and hot water.
 

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MagKarl

Seaman Apprentice
Joined
Jan 18, 2021
Messages
47
Right on, looks good to me. You have new exhaust manifolds too, I still have the old rear dump log style.
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Right on, looks good to me. You have new exhaust manifolds too, I still have the old rear dump log style.
Nope, they are the 'mid' era manifolds.

Early = Log and rear dump. (up to 1982)
Mid = centre rise, and 'wet joint'. (1982 to ~2002)
Late = centre rise and dry-joint. (from ~2003)

But the engine does have Vortec heads and a serpentine belt, so that puts in the in 1996-2002 era. Did the OP mention a year? Not sure about the drive and transom plates, the serial number tags (on the flame arrestor) are from the early 80's.

Chris..........
 
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scatgo

Petty Officer 1st Class
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Jul 13, 2014
Messages
370
Can somebody please go to this website and look at the specs on the engine? They are claiming 325HP @ 4000 RPM! Would you believe that?
 
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achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Can somebody please go to this website and look at the specs on the engine? They are claiming 325HP @ 4000 RPM! Would you believe that?
At the crankshaft, with MPI yes, but the one you photographed has a 2bbl carb, so more like 250hp (at the prop)....

Chris....
 

scatgo

Petty Officer 1st Class
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Jul 13, 2014
Messages
370
If a 4 bbl would fit that intake manifold do you think I would get much of a HP bump?
 
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