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OMC 250 (chevy 350) cooling System |
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almabes 
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Joined: March-20-2008 Location: Acworth GA Status: Offline Points: 263 |
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 Topic: OMC 250 (chevy 350) cooling SystemPosted: August-16-2009 at 9:39pm |
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Between Josh, myself and marine mechanic friend of mine we determined that four of those holes were extra, and basiclly adding confusion instead of helping cool the engine. They're probably there to accomodate a closed cooling system. Josh plugged all the extra holes in the manifolds with 3/4" NPT pipe plugs. It's more like the raw water colled PCM center rise pyramid setup now.
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'76 Martinique PCM 351W |
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Luchog
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Posted: August-15-2009 at 9:59pm |
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I'm glad you figured it out!!
Now, I think you can do well with any chevy 350 housing, just that you might have to cover all those holes on your manifolds! by the way, how did you do it? |
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jdmack0208
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Joined: July-12-2009 Location: Hope Mills, NC Status: Offline Points: 72 |
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Posted: August-15-2009 at 4:19pm |
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Ok so the boat is running on the hose, did not heat up and I left it running at idol for 20 minutes. Water is coming out of the exhaust as it should. The manifolds fluctuated from warm to cool, I don't know if that is normal or not. I am gonna have to buy a new t-stat housing because I couldn't seem to get the crack completely sealed. Gonna throw some more permatex on it and see if I can get is controlled. Of course the JB weld didn't hold once I tightened down the bolts. Researching the t-stat housing now.
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boat dr
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Posted: August-14-2009 at 2:43am |
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CorrectCraftParts has a set of used OMC late style manifolds for sale. Call Karen for prices and shipping. These are not after market fit all manifolds, but the real deal. 1-318-299-8547
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jdmack0208
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Posted: August-14-2009 at 12:47am |
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This is what I got from the guy that the guy I bought the boat from got it from(say that three times fast!) Not much help but at least he cares enough to email me back.
"Hey I believe there were 2 holes on the front of the old manifolds and the hoses went to the thermostat. I assume a newer style is being used now as the old one is no longer being made. You will probably have to get a different thermostat housing. Go to correct craft fan site and ask for a picture or to the manufaxcturer of the new system and ask for a thermo. matching the one you are using." |
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jdmack0208
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Posted: August-14-2009 at 12:45am |
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Ok here is the link to the manifolds I have, the file is a PDF and I don't know how to post it.
http://barrmarine.net/wordpress/omc-v8-4/ And here is the link to the risers: http://www.oscomotors.com/catalog/catalog31.asp It doesn't say anything about closed cooling system. I don't know, it won't stop raining here for me to get out there and hook everything up. |
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almabes
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Posted: August-12-2009 at 12:13pm |
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I have sent an e-mail to a marine mechanic friend of mine, and asked him to take a look at the pictures.
Hopefully he can help figure out the plumbing. |
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favorite computer wisdom: net helpmsg 4006
'76 Martinique PCM 351W |
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eric lavine
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Posted: August-12-2009 at 10:24am |
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I looked and it doesnt have half of the hoses you have. i dont think it will help
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"the things you own will start to own you"
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jdmack0208
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Posted: August-11-2009 at 11:22pm |
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I have all the thermostat and gasket but I got off work late last night and today it is raining so maybe I will get them in tomorrow.
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almabes
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Posted: August-11-2009 at 4:51pm |
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Josh,
Any luck running her on the hose? |
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favorite computer wisdom: net helpmsg 4006
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almabes
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Posted: August-10-2009 at 10:08pm |
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OMC:
Only More Confusion! |
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favorite computer wisdom: net helpmsg 4006
'76 Martinique PCM 351W |
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boat dr
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Posted: August-10-2009 at 6:03pm |
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OMC
Other Motor Company |
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almabes
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Posted: August-10-2009 at 4:01pm |
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OMC:
Obviously More Complicated? |
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favorite computer wisdom: net helpmsg 4006
'76 Martinique PCM 351W |
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eric lavine
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Posted: August-10-2009 at 10:13am |
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im taking my camera today and will snap a pic of a similar omc, it should give a general idea of hose routing
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"the things you own will start to own you"
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jdmack0208
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Posted: August-10-2009 at 12:49am |
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Don't worry though I have plenty of other stuff to fix(tach, speedo, depth gauge etc...)so plenty more threads coming and you'll learn a lot more!
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jdmack0208
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Posted: August-10-2009 at 12:44am |
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Well on a positive not, the boat ran strong until it overheated. No more bogging out. It never planed out though, what would be the reason for that? Speed?
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almabes
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Posted: August-10-2009 at 12:42am |
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Oh no...I'm working from home tomorrow...I guess that means I'm really checking this thread tomorrow.
Good luck. I've learned more about OMC inboards than I've ever thought I would. |
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favorite computer wisdom: net helpmsg 4006
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jdmack0208
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Posted: August-10-2009 at 12:41am |
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Cool, thanks....I will let you guys know what I come up with tomorrow. I will take the laptop out there with me and update this thread.
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almabes
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Posted: August-10-2009 at 12:39am |
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From what I see at various purveyors of OMC parts, I am, indeed mistaken. 160 degrees is the appropriate temperature thermostat.
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almabes
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Posted: August-10-2009 at 12:18am |
Unless I am mistaken, raw water cooled GMs run a 145 degree thermostat. with a 160 the motor will get too hot. |
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Luchog
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Posted: August-09-2009 at 11:57pm |
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He said the boat cooled correctly and you got a boat with a trashed impeller...
The thing is an engine can be run without any water (or an improperly plumbed system) for several minutes and it wont get hot, so the only way to test it's cooling properly is by pulling the hoses. |
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jdmack0208
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Posted: August-09-2009 at 11:45pm |
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The mechanic did say he ran it for a while on the hose while they were tuning it. With it on the hose the impeller wouldn't have mattered cause there was constant pressure. He said it was cooling fine. I will leave it the way he had it only with a 160 degree t-stat installed and run it on the hose for a while at idle. If the t-stat opens up and the motor cools then it should be good to go once I get the impeller in the mail. I really do appreciate all the help you guys are giving me. I spent a lot of money at the mechanic and really the only way this boat is gonna run now is with me fixing it with the help of guys like you.
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Luchog
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Posted: August-09-2009 at 11:39pm |
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First try it as is... the important thing here is to have good flow inside the engine for cooling.
Then you can try taking it away and see if it still works. |
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jdmack0208
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Posted: August-09-2009 at 11:36pm |
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I don't think hooking the water supply up to the top connections is the best idea as there are only two little holes in there to allow water through.
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almabes
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Posted: August-09-2009 at 11:35pm |
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I vote leave it.
On third thought, those connections at the top of the riser are to provide a one-way valved drain for water in the risers that could make its way into the dry side of the exhaust manifold. This is a strange setup. |
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jdmack0208
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Posted: August-09-2009 at 11:34pm |
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Once I get the t-stat in tomorrow I am gonna be ready to test. I should have no problems if I hook the garden hose up to the outlet hose of the impeller housing.
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jdmack0208
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Posted: August-09-2009 at 11:31pm |
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So water from the impeller to the t-stat housing, t-stat housing to bottom connections on the manifolds then leave the anti-syphon portion the way it is or eliminate it all together?
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almabes
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Posted: August-09-2009 at 11:31pm |
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Honestly, call Discount Inboard Marine on Monday. They will probably be able to give you a better answer about your cooling system.
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favorite computer wisdom: net helpmsg 4006
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Luchog
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Posted: August-09-2009 at 11:22pm |
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I dont know why you want warm water fed into the engine... I think most if not all engines running I have seen have water feed from the water pump directly into the engine and then into the exhausts.
You possibly have to inlets on the T housing and 2 outlets when a normal engine has only one inlet and 2 outlets (1 for each manifold) If the thing was not plumbed correctly and you cranked it, it might have ran without water... you also dont know what mechanic number 2 tried with it to make it work. SO first off start the new impeller, and then start pulling hoses. |
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jdmack0208
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Posted: August-09-2009 at 11:13pm |
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I opened it thinking maybe I had a bad T-Stat, turns out there wasn't one in there. I would like to eliminate some of the hoses too but what I cannot figure out is why I have 4 hose inlets going to the top of the t-stat housing.
Aren't the manifolds supposed to warm the water going in to the t-stat housing. Isn't the top connections on the t-stat housing basically an overflow that can be routed out the anti-syphon valve. Shouldn't the anti-syphon portion keep positive suction on the top portion of the t-stat housing? Tomorrow after work I will try to follow the water path and hook it all up. Once I get the t-stat in the boat will start right up as long as I am feeding it hose water. |
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jdmack0208 wrote: