More thermostat Stuff...

[andrewgroup]

My last post was about no thermostat. Everyone inspired me to determine if my crazy uncle had been running this boats with no thermostat. I took the thermostat housing off today and much to my surprise there was a thermostat in there but it had come apart giving the appearance of no thermostat.<br /><br />It has 143 degree stat and I will replace it with the same. However, This is a 1969 Mercruiser 225 HP, 327cu in engine and the housing has a lower part and the upper part. in the lower part are two sensors and I cannot find a diagram in either of my two manuals, Clymer and chilton marine that show two water sensors.<br /><br />I've looked at every diagram showing the various water houses on 1969 engines and none of them match what I have.<br /><br />I would love to know if we have any mechanics in the group with access to real old manuals. My engine is a 225HP 1969 with a Type II 1.78 - 1 outdrive. The engine serial number is 2638021<br />the outdrive serial# is 2558875..<br /><br />The reason is I read in one manual that removing the exhaust headers and soaking them in muriatic acid and rodding the headers should be done every 3 to 4 years to to 500 hours whichever comes first. And knowing my uncle he has never done this and maybe I should take the plunge but would want to get all of the gaskets before I ever considered doing this with the engine being older like this..<br /><br />according to an old document I found this engine had three ranges of serial numbers..<br />1539620-2278646 then 2278647-2694014 then 2314301-2639854...

 

[akriverrat]

Re: More thermostat Stuff...

do you mean check balls that you see when the hoses are removed as this shows...http://www.marinemechanic.com/site/PAGE260.htm or two water temp sensors as shown here...http://www.marinemechanic.com/site/page250.html

 

[andrewgroup]

Re: More thermostat Stuff...

The second choice is more similar. It shows two water temp sensors... I've traced the circuits and one temp sensor goes to the electric choke pull-off on the Rochester 4bbl carb. I did some testing and this component shows a near short in and around 80 degrees. it rises to 1500 ohms when heated above 100 degrees. This means it must allow the choke to engage at room temp and as it becomes a greater resistance the choke springs release the choke.<br /><br />The seconnd temperature sensor goes to the temp gauge, it starts around 1500 ohms and goes to around 80 ohms when heated in water to 180 degrees.. I'll substitute a high current resistive pot to test the accuracy of the guage because I have already plotted the opening range and rate of my new thermostat and the resistance of the temperature sensor....<br /><br />I'll know more later this weekend when I bolt this all back together..<br /><br />Thanks for the links...

 

[Bondo]

Re: More thermostat Stuff...

Well it sounds like you've taken care of the T-stat problem......<br />But this concerns me a bit....<br /> "The reason is I read in one manual that removing the exhaust headers and soaking them in muriatic acid and rodding the headers should be done every 3 to 4 years to to 500 hours whichever comes first. And knowing my uncle he has never done this and maybe I should take the plunge but would want to get all of the gaskets before I ever considered doing this with the engine being older like this.." <br /><br />I've Heard that when running in Salt, Risers,+/or manifolds need to be replaced at every 3 to 5 years......<br />I Know that you can get an honest 7 to 10 years out of a set when you play in Sweetwater.....<br />You've Already got 34YEARS out of them....!!! I'd be Worried about Rust-Thru.... It'd be Ashamed to Destroy that Old short stroker to a Rotten Manifold...!! <br />All that "Stuff" that you're going to dig, pick, rod,+ Burn out of those manifolds, USED to be Cast Iron.... <br />I'm Guessing that you have the old "log" style(Rear Risers)..??<br />Napa auto parts lists your manifolds(18-1950-1 port 18-1951-1 star).. They run from $245. to list of $382.79..... And a Conversion Kit that sets you up with the newer Center risers, With All the Tubing,+ Hardware(AP#5499)..... Don't have the price on this though....<br />H*ll at ebay there are small block Chevy/Merc manifolds listed All the time....<br />If you decide to under take the Cleaning route, I see Alot of "N/A"s on some of the manifold plate gaskets for your engine, in the NAPA book....<br />Good Luck...

 

[andrewgroup]

Re: More thermostat Stuff...

WOW,<br />That's some good info and I will being my quest to learn more about my options...Yes I have the CAST iron style manifolds. Something that seems unusual is that I can't find a drawing in my Clymer or Chilton marine that accurately depicks my manifolds. Most of the pictures show a hose going to the rear of the manifolds but mine only have one hose coming from the thermostat housing to the front top of the manifolds. In addition mine is a through the hull exhaust and the manifolds have a riser on the rear the goes up and back down slightly then straight out the hull.<br /><br />I'll look up the the part numbers you've provided because like you say...34+ years. Rodding and scraping the existing manifolds could do more harm that good, as well as doing nothing could equally result in the same in a rather unpredictable manner though...<br /><br />Thank for challenging and offer up great info and another valid opinion...

 

[andrewgroup]

Re: More thermostat Stuff...

Bondo,<br /><br />You've given me a quest. I hate quests. I've been to NAPA and they have a price 401.00 for each of the two part numbers you provided me. These come with no gaskets, bolts, or the risers. They are 237.00 each....Gee this could get expensive...<br /><br />You referenced an upgrade number but the NAPA parts dude, could find any reference to it, nor anything that looked similar.<br /><br />Aside from have manifolds that aren't about to rust thru, what would be the benefit of the newer center style manifolds?<br /><br />If you have some alternative places where I might research the cost of a complete set, manifolds, risers, gaskets, I would appreciate hearing about them....

 

[Bondo]

Re: More thermostat Stuff...

Andrew T.,<br />Have your NAPA guy look in NAPA catalog Marine Products #MSP-7 supersedes MSP-6 March, 2002..... page # 362, bottom of the page... part # AP# 5499....<br />The center riser manifolds are a more effeicent design.. a little cheaper in the long run...<br />Ebay is another option.. or even the Sponser of this board... If you're running Thru-Hull, you don't need the conversion kit... just come off the riser,+ straight out the back..... That's how I built mine...<br />In that case, You can get 2 part # 18-1997-1s,+ a couple of risers in the degree angle,+ diameter you need....<br /><br />BTW, your NAPA guy is quoting you a High List price.... He Should be able to do better than that... Talk to the Owner, or Manager.....<br />My cost is $245.77 each on the Log style Manifolds....<br /><br />Good Luck...