Running hot

[sweet 16 1966]

Over the last couple years, I have replaced the bellows and shift cable rubber. Gone through the outdrive and replaced any bearings, gears, waterpump and impeller. The engine is new. Replaced its waterpump very recently. 302 enging with Mercruser outdrive- pre alpha. Temp has shot up to 220 and likes 190. No thermostat. No cranking issues at any temp range. Engine feels like it may not be as hot as indicated although I do n ot want to count on that.
My thinking is the water hose which connects to the outdrove and is connected to the thru fitting in the transum is getting crimped and keeping enough water from cooling adequately. Pics do not show it as well as expected.

Appreciate any comments on this matter as to a fix for the " weak rubber waterhose" ??

[Morgan's Cloud]

The only time I ever had a 'hot run' situation like that (with the same outdrive/trans assy) it was in fact the hose you described as being the culprit. We used a non Merc straight pce of hose and it did'nt 'conform' to the curve the way it should have.
Definitely caused a kink that was hard to see and then up went the temp gauge !

[sweet 16 1966]

How did you correct? Its a merc hose I am using. I try to store with outdrive down when possible so it lowers the "memory issue" but to no avail.

[tmdog]

I am not going to ask why no thermostat. But the hose you mentioned goes to the cooler and directly to the water pump and thru the engine and out the exhaust. If you have thru transom exh., how much is exiting from the pipes? Do you have stock exh.? I suspect exh. riser manifold. Give more imfo. I see you are local. Has the boat been in salt?

[gcarter]

You know a simple, fairly inexpensive solution for this and the silting problem discussed elsewhere is a through transom water pickup. First, it's very hard to pick up silt from that high, and second, you do have a simple straight hose to furnish water.

[Cuda]

I'm a big believer in an offshore type water pickup. I have them on my 302, and on my 22 with the TRS. Keeps the water from being full of sand, silt, and such that is worked up by the props.

[MOP]

Only problem it is an Alpha with a drive pump, but you are 100% on transom pickups and inboard pumps!

[BigGrizzly]

The intake hose you mention ususlly colapses on the inside. and can't be seen (in most cases) from the outside. this is an early boat which makes it real possible. First make sure it is really overheating and not the guage or the sending unit. A lot of times if a sending unit is overheated it may read high constantly especially if it is the thermowax variety which was stock back in the early boats. Un like Jim I want to know why the thermostat was removed. In that motor (depending which setup you have,there are at least 3 that I know of) you may need a t-stat for proper colling. I am local and live on Lainer and I have inferred temp guage we can test the real temp of the block. My Corsican runs at 190 on purpose I set it up to run this temp. under no circumstances should it run less than 160F and I don't care who thinks this is wrong, it is correct!!! I will explaine it over lunch or dinner. I won't do it here again because I have done it here 4 times since 1998. We can fix it providing it is broken.

[Cuda]

The intake hose you mention ususlly colapses on the inside. and can't be seen (in most cases) from the outside. this is an early boat which makes it real possible. First make sure it is really overheating and not the guage or the sending unit. A lot of times if a sending unit is overheated it may read high constantly especially if it is the thermowax variety which was stock back in the early boats. Un like Jim I want to know why the thermostat was removed. In that motor (depending which setup you have,there are at least 3 that I know of) you may need a t-stat for proper colling. I am local and live on Lainer and I have inferred temp guage we can test the real temp of the block. My Corsican runs at 190 on purpose I set it up to run this temp. under no circumstances should it run less than 160F and I don't care who thinks this is wrong, it is correct!!! I will explaine it over lunch or dinner. I won't do it here again because I have done it here 4 times since 1998. We can fix it providing it is broken.

Running those high temps are fine for freshwater usage, but if you ran those temp in salt water, you'd have trouble. Salt water forms crystals VERY quickly at temps over 140.

[sweet 16 1966]

Well, I have to give much thanks for your responses. I have not run a thermostat for years. If this is wrong, advise and I will correct. The first thing on my list today is to go to Holiday and get a new impeller just to be safe. Then I was instructed by a mechanic friend to pull the hose off the waterpump and while running, it should emit a 6" water spout if properly pumping. That would eliminate the hose from being the culprit if all is OK.
He also said Merc had hot issues on the 470's w/o a thermostat for it to cool properly-why, I don't know. I could then replace the sending unit, all are SW gauges so maybe the sending unit does not match up? Tune in around lunch time and I will advise progress. Big Griz, lunch or dinner anytime on me!
Tom, I owned since 1980, I am from here but lived in Va and Texas. This boat has seen the battleships at Norfolk Va. , rode in the Patomic river. Been up the James river to Jamestown. ( also , the San Jacinto river was fun)- 1988-1991. It has seen and smelled the strange odors of the Houston ship channel and I believe it saw Galviston in its days but that was long ago. Recently us Seadogs ran the St. Johns River, then Lake Cumberland. The manifolds seem to allow enough water to pass but who knows. If all seems OK, Manifolds may be next. BTW, It does not feel hot when the gauge shows 220, cranks well and seems happy but I wonder. Off to the shop.

[sweet 16 1966]

Engine shot.

http://www.donzi.net/forums/attachme...3&d=1139882446

From 2004 when I re-corred the deck. Like I have nothing else to do!
Not a fun job. This is a labor of love which I hope to one day put into a 22.
In the mean time , work continues on the 16.

[sweet 16 1966]

BTW, this is a very old boat. No clam shells, came with an eaton outdrive which I tossed in 85 . Not a fan of them.

[BigGrizzly]

Ok you8 have a 1965 16 and the origional drive was the Eaton probably the one with the shift cable on the top. You switdhes to the Merc pre Alpha probably a 120. Your friend said they had trouble with the 470 cooling without the t-stat. 470 refers to the mer4c 470 engine which is half a 460 ford and is no longer in production exceot in car racing. all thoes were fresh water cooled eith the cooler in the exhaust mamifold. I don't remember this engine ever in a Donzi. I have always though it would be a good match and 2anted to build one. Power and fuel econony are great with that engine. As I said we can fix that problem. Come-on down. Give me a buzz, I live on the lake(Lainer) around War Hill Park cell 770-318-1136 home 706-216-8194.
Cudaou are a little conservitive 180 is the christalization point of salt in your area it attacts the exhaust at the riser-hottest point. if the engine temp is 180 the water on the raw warter system would be about 150 heat transfer etc stinks. However it is a small concern if unit is flushed out. Me I only have closed cooling systems and the exit water is never that high and has never been a problem since the early 1960's which is when I switched to closed cooling. Reason for switching was other issues in a cruiser, open system and salt related

[Cuda]

Grizz, my father was a chief engineman in the Navy for 23 years. He said they had to run all things at 140 or less for cooling. The salt crystals would form and block the small cooling passages.

[BigGrizzly]

Cuda . not to say anything about the Navy or what your Dad says but the Navy teaches what they think they have learnrd on the old ships with big engins and hot running with big deisels or steam engines that run hot and long. All the boats I have run have had 160 T-state, I wasn't going to get into it but I will. Factis if your engine runs at140 F or less your engine wear increases over 40% and extensive slug build up. These experiments were done by GM in the mid 1960"s and again in the late 1970's. In 1982 Honda had us do the same tests with the same answers. like I said the water temp in the exhaust of a 160 degree T-stat ed engine is not a 160 degree. The T-stst works by monitering the temp in the engine and mixing cold raw water with it to matain a nominal 160 degree in the engine. inorder to crystalize water also has to be moving slowly with steam pockets. After working with some engineers at Honda you would be surprised what misconceptions science used to preach. Another false hood is a supercharger in a 500HP big block boat can't be closed cooling "it will run too hot". My Criterion runs at 170 (safty margin for bad gas and clogged sea strainer) and has since new. We have built several with over 800HP the same way with no cooling system related problems. Granted these are modern full flow systems. Theories that were gosphel yesterday are not true to day. When I was a kid, household voltage was110 volts and 220volts, then in the 1960 it was 115v and 230 volts now it is said to be 120v and 240v. Fact is it has always been 118v and 236v average depending on line drop etc. I am not going to get into another discussion on these subjects. Do what you feel is right and I will do what I feel is correct. We can talk more at Eufala.









dadyour