95 4.3lx alpha one mercruiser cooling system question

Jgcrock99

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May 14, 2018
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I'm Familiar with vehicles but I'm a newbie to marine stuff. Is the riser like a check valve? What am I looking for?
 

Jgcrock99

Seaman
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May 14, 2018
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You said check balls and Springs at risers. I'm not familiar with these and I'm struggling to find a YouTube video of it. What am I looking for there?
 

Bondo

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You said check balls and Springs at risers. I'm not familiar with these and I'm struggling to find a YouTube video of it. What am I looking for there?
Ayuh,..... Welcome Aboard,..... Tell us more about Yer issue, so we can help,.....

The check-balls mentioned live in the t-stat housing,.....
 

Jgcrock99

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May 14, 2018
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Ayuh,..... Welcome Aboard,..... Tell us more about Yer issue, so we can help,.....

The check-balls mentioned live in the t-stat housing,.....
Original post said it all really. It was strange, winterization went fine, antifreeze drew in without issue. Summerizing went fine, clear water came out as it should when flushing the system. Changed oil in motor and lower unit (did lower unit for winterization but got the wrong juice so corrected for summerizing). Ran the boat for over an hour. Mild hesitation here and there but she needs spark plugs and it's old fuel. Parked for about 45 min to eat dinner. Fired up to come in and no waked for a few minutes and my alarm went off. Shut it down for a little bit and checked raw water inlets and they were clear. Had no issues on the water so thought maybe a malfunction so I fired up again and started watching the gauge and it hung around 220. Thinking it might be a weird air bubble I planed out and it immediately cooled down to 125. Ran for a few and idled again only to watch it climb again so I headed to the ramp and as long as I was at speed it stayed at 125. No wake zones it crept up to 180+.
 

dubs283

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You said check balls and Springs at risers.
I mentioned check balls/springs at the t fitting, meaning upper t stat housing. Of which a hose routes to the riser in a lot of mercruiser cooling systems

Was guessing towards commonly seen cooling systems in my world based on your first post. My bad for assuming however given your limited info my mind treated the situation at 50/50 on your knowledge of mercruiser cooling systems.

It is now known folks here will have to most likely rely on pictures and oem s/n to guide you properly
 

Jgcrock99

Seaman
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May 14, 2018
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I mentioned check balls/springs at the t fitting, meaning upper t stat housing. Of which a hose routes to the riser in a lot of mercruiser cooling systems

Was guessing towards commonly seen cooling systems in my world based on your first post. My bad for assuming however given your limited info my mind treated the situation at 50/50 on your knowledge of mercruiser cooling systems.

It is now known folks here will have to most likely rely on pictures and oem s/n to guide you properly
Should I just replace the housing and t-stat?
 

dubs283

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Should I just replace the housing and t-stat?
Like bondo says feel free to replace any parts you like but without troubleshooting the issue it's a guess as to what components have failed.

First item I would check based on your issue is the check balls/springs at the t stat housing leading to the risers, this is of course if your engine/cooling system is designed to use the check ball/spring system

S/N and pictures help greatly here for folks to determine best course of troubleshooting your specific setup
 

flashback

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Jun 28, 2002
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Impeller is a big possibility and is the first place I would look and if you go to the trouble to look you should change it.
 

Jgcrock99

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May 14, 2018
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Ayuh,..... It's yer boat, you can do as you please,..... But,......
Here at iboats, we prefer to Diagnose issues, rather than just throwin' parts at it, 'n praying,.....
I understand and agree. However, this boat is a 95 and while I assume the tstat has been changed before I'm betting the housing is original. If I'm going through the trouble of checking the mechanics of a 30yo boat part I may as well change it while I'm in there. I've had it since 2016 and haven't had anything done with the cooling. Had the impeller changed 2-3 seasons ago. Someone said my boat likely doesn't have the check ball system however. My sn should be 0F001220 - 0F601126 range. Can't get in there right now to make sure.
 
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Jgcrock99

Seaman
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May 14, 2018
Messages
66
Impeller is a big possibility and is the first place I would look and if you go to the trouble to look you should change it.
Probably gonna troubleshoot it when I get a chance. Set it up like I'm gonna winterize and see if it draws from the bucket. Just weird, winterized and summerized without issue till I took it out on the water.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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If it's a fresh water boat, the housing will outlast your grandchildren. Why throw money at parts that may not need replacing vs trouble shooting?
 

Jgcrock99

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May 14, 2018
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OK, so I finally got a chance to get I to troubleshooting the issue. The impeller seemed to be drawing the water just fine, at idle I drained a 5gal bucket in about 2-3 min. Water seemed to be glowing fine but it began overheating again. My next check is the thermostat. I honestly don't think this boat has one because I've owned it for 5 years and it's never gotten above 120° until it overheated last month. Is there a way to check the actual water pump? On a vehicle you can take the coolant cap off and see the water circulating through the radiator, is there any kind of check like this for the water pump of a sterndrive? It's a 1995 4.3lx mercruiser with an alpha one. Coolant system is a design 1.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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Don't try to suck water from a bucket. You will toast your impeller.

Water needs to be above the impeller to prime.

Always use muffs or have the boat in the water
 

Jgcrock99

Seaman
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May 14, 2018
Messages
66
Don't try to suck water from a bucket. You will toast your impeller.

Water needs to be above the impeller to prime.

Always use muffs or have the boat in the water
Yes, bucket was above the outdrive on the sundeck, I used it like I did to winterize with a hose running to double sided muffs. Nearly 4ft drop to the intake.
 
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