Engine Cooling

[chrisheile]

I just know that if any petcock is open that the boat does not cool properly.  Neighbors had a Sport Nautique that kept overheating at an idle.  Took us forever and replacing an impeller (which was starting to get ugly anyway) and a spidery (cracked) water filter case and two trips to the marina to figure it out.

[Joel]

Is 180 degrees NORMAL with a 160 T-stat???  Mine runs at 180 degrees at speed / planed, but cools to 160 degrees at idle.  I'm thinking its time to change the impellor.  Its a Johnson impellor and it looks kinda small for a engine this big, but what the hell do I know...  The impellor looks fine upon inspection, but maybe the rubber "fins" are getting to the point where thier laying down & doing more spinning than sucking up water at a higher rpm...  I dont know, but I'm gonna get a new one anyway...  I'll let ya know the results.

Thanks,   Joel

[John Doerfler]

Well Joel you know I have racked my brain all summer trying to get this new motor cooling right with a Tstat in it.  I have had the entire engine and all the components with it refurbished and restored with new parts.  No ideal why I have to drill holes in a 160 stat to get a 180 temp all I know is 180 isnt to hot and I have had the boat out on the lake twice since I did that and it holds 180 all day long.  But I would still like to know why I have to deviate from the stock set up to get this thing to cool?  Waiting for god to drop from heaven and give me the answers!
John Kyle Doerfler

[Joel]

That could take a while...  I think He prefers "puff boats" to stink boats...  He tends to stick with natural powerplants 

Ron said to me 2 seconds ago that 180 is NOT normal...  This is what I described to Ron:  "I had it on the hose today (very cold water) on a fake a lake (plunger type supply) - checked all the hoses, etc, no blockage that I can see and the T-stat didnt want to open fully.  The top of the housing never got hot, the lines to the exhaust never got hot, the waterpump hose (big fat one - I think it is a return hose) on stbd side of engine was plenty hot although the temp still went up to 170 or so on my temp gauge..."

Ron's answer:  "180 is NOT normal.  Start at the water intake grate on the bottom and work your way to the engine.  Check the inside of the water-intake grate (be sure it isnt blocked in any way).  Check your sea-strainer (water strainer) for small cracks and make sure the gasket is in the top when you put it back together, ensure all hoses are double clamped.  Check your transmission oil cooler - take off the water (not the oil) supply & return hoses, shine a light through one side & hold a mirror to the other side of the unit.  You should see through it very clearly - you may need to clean out the small pipes inside (use pipe cleaners).  Next, check the supply hose to your impellor for blockages.  Check your impellor to see if its serviceable (not cracked, etc) - crank over the engine once to ensure your impellor fins are folded over in the direction of the crank (they could be folded backwards - it will pump water but not well - it happens)  Check all hoses leading to the thermostat, the water (circulating) pump, and the exhaust risers for blockages.  Check your T-stat and/or replace - while doing this check all openings to the housing & the manifold for debris, etc...  Make sure your T-stat bypass hole (about the size of a dime in my boat) is not plugged.  Put it all back together and make sure you use gaskets or gasket maker for good seal on the implellor & T-stat.  When its time to test the engine, use a 5 gallon bucket with a supply hose from the house into the bucket and route your intake hose from your strainer into the bucket.  Throw away the "Fake-A-Lake" as the water pressure from your house could screw up your impellor..."   Damn thing costs me some $$$$

[John Doerfler]

Hey Joel,
  What your describing to me is exactly the same thing that is happening to my motor.  Again, I have been through it all VERY thoroughly and a normal Tstat will overheat the engine.  However, I havent tried a 140 stat.  Ron told me to give that a try and see what happens.  I will try it tommorrow if I can find one.  Its funny I have felt all the areas your talking about for heat and mine does the same thing.  Its like all the cold incomming water just goes right out the dime sized bypass hole in the cooling block.  Joel,  I am a mechanic so I can assure you that I have given this a thorough going through.  About the 180degrees I dont think it will hurt anything.  Ron told me that guys would run a 180stat to get a little extra power.  My truck runs at 200degrees.  But I would really like to have it at 160.  You know the 160stat with the four holes drilled in it gets to 180 really slowly then at 180 it varies up and down a little like the Tstat  is opening and closing.  I cant help but think that you have really cool lake water flowing over the top of the stat and that transfers heat through the metal of the stat and cools the bottom where the hot water is not allowing it to work properly.  In an automotive engine the water going over the top of the Tstat is hot as well so you dont have as much of this affect.  I dont know! At this point I feel like I dont know anything.  Will try that 140 stat tommorrow like Ron said and let you know how it works.
John Kyle Doerfler

[Joel]

I did the above procedure right after I talked to Ron & posted it...  I found some clear plastic pieces inside (top) of the oil cooler on the output side of the sea-strainer.  Looked like hardened sealant and how it got there is anybody's guess so its well worth checking out...  The oil cooler itself was clean so the strainer is definitely doing its job.  I'm sure those pieces restricted the flow a bit so THANK YOU RON, but it still goes up to 170 F on hose water - pretty cold out of the tap.  Of course the temp sending unit and/or the gauge may be off, but it seems to respond pretty well to temp fluctuation so I'm thinking its O.K.

I guess this is gonna have to do for now - I've got to go skiing on Thursday.  Try NAPA...  I've been everywhere else and a 160 F T-stat is all I can find.   One guy told me that 160 is as low as they go...  I'm sure Ron knows what he's talking about but a 140 T-stat for my Indmar 351 is as easy to find as hen's teeth     Let me know if you find a 140 T-stat and where you found it!

Of course, life is pretty good if this is the biggest problem weve got!   LOL!!!!

[Mike Harry]

Joel, if you need one and cant find one let me know. Ive got a buddy in the parts buisness (auto zone) and he got me the 140, somewhere around 12 bucks.

[John Doerfler]

Right On Joel, life cant get any better than when your one glassy water on an American Skier.  I'll keep you updated man.
John Kyle Doerfler

[Joel]

Gongchuan,

Those are the @$$#%^!!! guys that told me the lowest temp listed on "the computer" was a 160 F T-stat - "they dont make 'em any lower than that for a 351 Ford..."   If you got a 140 F T-stat for me, the shipping would cost 1/2 the price of the part    Can you get me a part #, etc, so I can go to there and ask for a specific item???    I may pull the damn thing out and go "Commando!"     Seriously, I dont think a lake with 84 F water is gonna cool it down to the point where its gonna effect my performance tooo much...

John,

Keep me in the loop on what you find as well...

Thanks guys!

[Mike Harry]

Ill get it for you today brother

[John Doerfler]

News Flash!!!!!  I think I may have discovered whats wrong with my boat!!!!!!!!  Just talked to Ron today and we got to discussing it and I think my Jabsco pump may be insufficiently providing enough pressure.  It flows lots of water without a Tstat because there is little to no restriction and when you put the Tstat in, the water back pressure is to much and it flows down the path of least resistance and out the exhaust bypass hole and not through the engine.  Its a long story as to how we reached that conclusion but lets just say I tried to modify the pump to work with a different impeller.  It flows lots of water but wont build pressure like it has to when you introduce a Tstat.  WOW!
Going to buy a whole new impeller pump and see what happens.  As for the 140stat.  I think I will just stick to the 160 if all this works.  I would like it to run about 160 and not 140.  In the mean time what I have works OK and I will be tearing up my feet on the water this weekend.
John Kyle Doerfler

[Joel]

Very COOL!!!!  I just read Ron's post about the different impellors (Johnson / Jabsco).  I'm thinking I have the correct impellor cause I can barely squeeze that bad boy in there and it comes all the way, flush to the front.  I have to push on it a bit to get the pump cover on...  But then again, I can find no practical solution to the slight over-heating...  Soooooo...  I'm buying a new impellor from a local supplier who spent about an hour researching to find the "right" one for this pump.  We'll see - it should be in tomorrow, but I'll be on the lake tomorrow    Maybe Friday!

Gonchuan is gonna get me the part # for the 140 T-stat so I'll get one of those too...  the cost like $12.00.

Keep me posted!  I'll do the same    Thanks Guys!!!

[RonT]

If you are not pumping sufficient volume/pressure from your raw water pump into your motor a 140deg. stat will not make a difference. Inboards have a bypass that allows water to flow out the exhaust 100% of the time the pump is turning, therefore water will take the path of least resistence, if there is a t-stat in the way the under pressurized water will simply go out the exhaust.
Years ago I remember troubleshooting this very problem, customer did not want to buy a new pump, I took off his raw water discharge hose from the t-stat block & started the engine, water came out fine until I put my thumb over the hose and very little volume/pressure appeared. After changing the pump the same test resulted in spraying water nearly 50' to the neighbors pier (under thumb pressure). His cooling problems were corrected.

Here are the Book Ratings for a typical Johnson F6B crank driven pump on a Small Block Chevy:
1000RPM =  9.5  gpm
2000RPM =  19   gpm
3000RPM =  29   gpm
4000RPm =  34.5 gpm

[Mike Harry]

Bad news Joel. It turns out the t-stat I got from auto zone was a mistake that they only had one of. I guess it had been on the shelf "FOR SOME TIME". sorry man.

[Joel]

Ron,  I'll stick to with the 160 T-stat and keep looking...  I replaced the impellor-pump discharge hose to the T-stat today.  The old one was pretty short with a tight bend and I'm THINKING it could be restricting the flow...  I can only hope that its something that SIMPLE!!!

Gonchuan, Thanks for trying buddy!

You guys are the best!!!