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clayman
03-21-2004, 11:05 AM
Hello everyone,
Many of you know my boat, a 1986 18' classic. Ever since I bought it, and the main reason the kid sold it to me was it overheated erratically. It has never been much of a problem for me at home because I live on a small lake, rip around a few times and put it away. But anytime I have taken it some where that requires alot of idling, like the St Johns river with the dam no-wake zones, it will sometimes over heat. As soon as it gets to 200-210 I shut it right down, and let it cool. Start it back up and its fine. Yesterday I performed some tests. I ran around the lake fine, no problems runs at 160. I tried to idle across the lake, in one minute it goes to 180 to 200 to 220, it get back on plane (or just rev engine in neutral @2000 rpm) and it drops right back down to 160. I have replaced the drive impeller, checked the hoses and belts, and flushed the block at the petcocks on the block. It has a brand new 143 temp thermostat ( which I have replaced a dozen times trying to figure this out.) The motor also has Stainless marine headers and elbows. I haven't replaced the motor water pump, but it looked fine when I had the boat apart. I ran the boat for about an hour yesterday both using the muffs on the drive and backed into the water on the trailer. both yeilded the same results. I noticed while on land and using the hose there was water leaking from the front of the drive around the bolt area just in front of the shifter linkage? See picture. and also there was pretty good water running out of the space between the drive and the prop. Could this be the root of all the evil? to much water leaking out at idle to cool the motor? Are these simple to fix or am I looking at a bill from the repair man. I hate taking my stuff to mechanics, but I might bit the bullet. I also notice there was more water coming from the starboard side exhaust and alot more steam/smoke. sometimes the smoke came in puffs. Valve adjustment? does anyone know of a reputable machanic in the Orlando area? Well, thanks for any advice any one can give. I really want to take it to Mount Dora next week, but I won't until this is figured out.
Jim
www.clayman,com
www.echelonmotorcycles.com

Rootsy
03-21-2004, 11:19 AM
ok lets see if we can help you narrow things down... it is my belief that you have a flow problem and not a mechanical engine problem. it overheats at idle but not when underway above idle... it overheats under load and not under load at idle... therefore lack of flow at low rpm...

a few things taht can cause this...

1. clogged passages
2. KINKED hose from drive to transom plate - if replaced it must be a specific length.. like 12 1/2 or 12 3/4 inches i forget.. but it must be cut EXACTLY to length.
3. Delaminated or kinked hose from transom assembly to engine circulating pump... replace it cause you won't be able to tell unless you cut it in half...
4. pieces of impeller stuck inside of the system somewhere
5. the little check balls in the thermostat housing...
6. bad circulating pump (less likely)
7. cracked or leaking transfer tube from water pump to driveshaft housing int he drive.. wehre you see water pouring out of... there is a copper tube and a couple of rubber grommets...
8. restriction between water pickups and pumps
9. thermostat in backward?

if it was an impeller you'd be ok down load in an unrestricted system but on top the flow would drop off as pump loses efficiency and flow becoomes inadequate to cool... at low rpm it doesn't have a whole lot of head so if you have an upbound restriction it can't push enough water.. but as soon as you rev it up it builds head and can overcome the restrictiont o supply enough water.

lets see a few shots of the engine plumbing...

ok someone add to the list...

JR - FLUID MECHANICS GIVES ME A HEADACHE...

MOP
03-21-2004, 11:22 AM
Sounds like you have the stuff changed, try this get about 2 feet of clear hose insert into the line coming from the drive. Get someone to go for a ride, watch for bubbles in the drive hose which indicated a leaky water tube gromet in the drive. After that test put the hose from the thermostat housing to the riser and watch for bubble there. There are a few things after the drive that can allow air into the system, usualy hose connections or cracks.

Phil

clayman
03-21-2004, 11:39 AM
Man you guys are on the ball. that wasn't even ten minutes. Anyway, here are some more pictures. As for the thermostat, it is in correctly with the brass sleave? and gasket holding it down. When I feel the hoses coming from the thermostat housing , they don't feel solid, I can pinch them flat and feel water flowing though. I am going to change all the hoses for good measure anyway. How about the leaking drive? is that normal? I will pull the lower unit tomorrow and replace the gasket and check that tube.
Jimhttp://donzi.net/photos/jspiroff43.jpg

clayman
03-21-2004, 11:41 AM
also, all four of the hoses from the housing go to the bottom of the exhaust manifold, and then a small rubber elbow goes from the top of the manifold to the elbow per the directions from Stainless marine.

Rootsy
03-21-2004, 11:55 AM
the transfer tube should NOT leak... As MOP stated.. it can suck air... a small amount of water leaking from around the vertical driveshaft out of the water pump is normal though...

rickrsbro
03-21-2004, 12:02 PM
a couple other possibilities for low volume at idle speeds...........

i would look at the o-ring between the upper unit and the gimbal housing( the gimbal would be flooded with water), the plastic impeller housing may be cracked (20-22 inch pounds mounting torque? check that #) and the seal between the upper and lower units for the water passage.

from your photo, i would bet on rootsy's #2.

MOP
03-21-2004, 12:35 PM
Most all of us are trailer Rats, the gromets going bad are more common on trailer boats. If you start with the clear hose first you can isolate, if before or after the drive. My hunch is the tube gromets, but what throws me off is being able to rev it and it goes away. That gets me up to the T stat like Jamie said the ball vavles in the T stat housing, if balls are worn or if springs are bad they will cause what is going on. Are U Having Fun Yet!

DONZI
03-21-2004, 12:49 PM
One more thought.
If you have a transom flush.
Ck.the internal plunger on the ck.valve to see if it might not be partially closed.

Murphy
03-21-2004, 07:20 PM
Which gasket are you using on the thermostat? The one that blocks the bypass completely, the one with a small hole, or the one that does not block the bypass? Checkout notes on gasket applications here.

http://www.mooreperformance.org/Five.html

Murph

BUIZILLA
03-21-2004, 07:52 PM
I had the same exact problem with my SS drive. I had the water leak out the front in the same exact place. Drop the lower unit and study the WP gaskets and spacer plate closely, paying attention to the water routing in the drive. One of my gaskets was wrong in the kit.

Jim

Woodsy
03-22-2004, 06:49 AM
Possibly a new temp sender in the block? maybe intermittent grounding issue...


Woodsy Von Outboard

clayman
03-25-2004, 09:05 PM
Update,
I pulled the drive and found that the seal that the upper part of the copper tube goes into was basically gone. I replaced it and went for a spin. At first it seemed to be putting out a lot more water and was keeping right at 160-170. I idled across the lake again and it began to run hot (190) by my dock, so that was a little dissapointing, but about a 15 second rev at 2000 rpm dropped it very fast back to normal. So I am on the search for a small leak somewhere. I am going to try the clear hose thing tomorrow bypassing the flush tee and the steering cooler to see what happens.
Jim
trying to get to Mt-Dora

RedDog
03-25-2004, 09:43 PM
Hello everyone,
...because I live on a small lake, rip around a few times and put it away...

Clayman - hope your trouble shooting works out soon! A boat as fine as yours needs to be on the water more than a short rip-around. :checkered

MOP
03-25-2004, 09:52 PM
Something Mad Poodle and I were discussing the other day may come into play. The rubber that most hoses are made of are quite corrosive, something I learned a long time ago was to brush gasket compound on the nipple and inside the hose then slip it on and clamp it. Do you have a Volvo drive? They are famous for rotting the inside water connecter which is aluminum, if you do have a Volvo check it out they will suck air and usually leak sea water in. Each and every hose connection should be gooped to protect the metal part it attaches to.

DONZI
03-26-2004, 05:30 AM
So I am on the search for a small leak somewhere. I am going to try the clear hose thing tomorrow bypassing the flush tee and the steering cooler to see what happens.
Jim
trying to get to Mt-Dora

Jim,
Remove the hose from the top of the Flush by/pass tee and unscrew the top.See if the plunger has returned to the top and if it moves freely(push on it).Then remove plunger (spring under).Clean & lube plunger.
Worth a try. Keep us updated.
Ken

MOP
03-26-2004, 07:53 AM
? If it is a Merc, have you checked the balls and spring assy in the thermostat housing! They must be round with little to no wear showing, you can turn the good side toward the housing if worn. My gut is it has to do with the balls being as it cools when revved. The tention needs to be set correctly refer to Merc Manual.

Rootsy
03-26-2004, 08:00 AM
Phil,

as you know, if those little plastic check balls get HOT... they tend to melt a bit... and will form a ring in them or worse and then tend to stick in the passage they seal... these are spring loaded in the closed position so water pressure forces them open.

MOP
03-26-2004, 08:14 AM
Most every time a Mecr over heats the balls should be changed like Jamie says they melt, but if you goose it they will come loose and let the water flow.
I was looking at the housing damage by the prop, that grayinsh look is electrolysis your zinc may not have good contact. When installing zinc on the outdrive it is a good idea to run a tap into the hole to clean it and also use a S/S star washer under the bolt head, they bite into the metal and help to get good electrical contact.

clayman
03-28-2004, 11:14 AM
Hello everybody,
Jennifer and I had a great time on Lake Dora with the crew yesterday, I counted 15 Donzi's. Our boat ran great dispite the overheating and the intake manifold gaskets failing that I just installed until 1am friday night before the run. I didn't put any RTV on the main parts of the gaskets , it didn't say to in the instructions from Felpro, but it is leaking oil all over between the manifold and the valve covers. Anyway, boat ran great, I love running on "bigger" water than my stupid sink hole lake I live on. But, going through the dora canal I had to put it in neutral and rev 2000 for 15 seconds to get it back down in temp about five times. About this ball thing? there are no balls on my thermostat housing? I had never seen them before until I checked out the web site someone suggested earlier. Could this be my problem? Also, I am running the gasket that completely blocks the water flow on the top thermostat housing. I checked with the Merc dealer and he said it was the right one. IS there a minimum water pressure from the drive? Could I some how put a pressure guage on the hose? I did the clear hose thing on friday. I ran it directly from the connection on the gimble/transom to the water pump on the motor, bypassing the flush tee and the steering cooler. it filled up solid, and stayed that way. I did see very small bubbles flowing by. Does this indicate an air leak in the system in the drive?http://www.donzi.net/photos/jspiroff86_rally.jpg

MOP
03-28-2004, 12:36 PM
Clayman you should see no bubbles especially sitting still the hose test is best done running, many time you see little to no bubbles until the boat comes on plane. When the boat is at rest the tube and grommets are under water, when you come on plane that cavity drains out and lets it suck air.

MOP

Murphy
03-28-2004, 03:37 PM
Assuming you're running stock manifolds with two hoses, one going to the manifold and the other to the riser, I'm thinking it's the Tee with no balls. The way it works, when the thermostat is closed (cold), it forces these open to bypass water to the manifolds. As the thermostat opens, the springs force the balls back into the T and the water flow is routed through the thermostat, which has a smaller opening. Very cool self balancing system actually. I definitely think you should try getting your Tee some balls and see what happens. By the way, what temp thermostat are you running?

Murph

MOP
03-28-2004, 06:16 PM
This is what your T Stat should look like!

MOP

Murphy
03-28-2004, 09:03 PM
OK Phil, you gotta stop scrounging in those scrap yards all day. That baby's off a coal-fired sidewheeler. Probably still works good though. The one on my 86 looks exactly like this one here...http://www.mooreperformance.org/Five.html

Murph

MOP
03-28-2004, 09:17 PM
OK Phil, you gotta stop scrounging in those scrap yards all day. That baby's off a coal-fired sidewheeler. Probably still works good though. The one on my 86 looks exactly like this one here...http://www.mooreperformance.org/Five.html

Murph

New balls old balls, as long as it has BALLS :biggrin: :biggrin:

MOP
03-28-2004, 09:22 PM
I have seen guys substitute 3/8 hole S/S washers by putting them against the opening putting the hose on with an extra clamp just off the nipple to hold it in place. That is basicly what OMC has done for years, just restricted the outlet.

Phil

clayman
03-28-2004, 09:25 PM
I looked through the manual and found no reference to balls on the thermostat housing. But for $150 bucks I think I will give it a try. I wonder if they just sell the brass tee with the balls? I am going to try the clear hose again with someone in the boat to better observe the bubbles. But if it should have no bubbles, then I think it is safe to say I still have a problem in the drive area? A friend asked me tonight where the PCV valve was? I said I didn't think boats used them. Is this right? am I missing something else as well? how does the crank case vent?
Jim
http://www.donzi.net/photos/jspiroff75.jpg

clayman
03-28-2004, 09:31 PM
I could try that MOP just for a test anyway.

MOP
03-28-2004, 09:46 PM
You already have the T just buy the ball kit assy and put it in, then you too will have Balls! :biggrin:

MOP

Murphy
03-28-2004, 10:52 PM
This is definitely worth a try. Between getting balls and putting gasket compound on nipples this thread is getting better all the time. Would that be the edible kind of thread compound by any chance MOP?

Incidentally MOP, I was outbid by $10 within the last 10 seconds of the auction on those GILS. I almost stole a brand new set for $750. Damn cyber punks.

Murph

MOP
03-28-2004, 11:30 PM
I shot one bid at 1 minute $800 bucks damn slow connection, the fellow that got them also got the last set I was intersted in, I think he may have a shop.

Oh well more Ebay dancing unless I can get a deal on new!

clayman
03-29-2004, 10:23 PM
Who would have thought, for $4 you can buy a set of balls!
they are on the way, if that fixes the problem that would be sweet.
Jim

clayman
03-30-2004, 08:36 PM
I am still curious about the PCV valve? should there be a hose from the valve cover to the intake manifold? I don't know if I said this already, but the intake manifold gaskets I installed friday failed on saturday. My friend thinks it is to much pressure in the block forcing oil up and out the gasket.
?????

Jim

gold-n-rod
03-30-2004, 09:19 PM
Who would have thought, for $4 you can buy a set of balls!

Much cheaper than here: http://www.neuticles.com/index1.html

Then again, they are priced by size!! :eek:

goldnrod

Murphy
03-30-2004, 09:21 PM
My understanding of the process is that during combustion a small amount of the gas/air mixture (including oil) gets past even the best piston rings. This is called "blow-by". In older vehicles this was vented to the atmosphere and caused pollution which is why the newer vehicles have a PCV valve. The vent is connected to a hose that leads to the air filter. This recirculates the ventilated fumes back into the engine. Mostly, it just gets your air filter dirty. The only downside I know of when using closed valve covers is that you're recycling these fumes back into your oil and it will get dirty faster. I don't think this could be a cause for your failed intake gaskets. If you're engine is overheating and you have an aluminum intake, I'd be thinking about that as the possible cause of a manifold gasket failure. The different heating/cooling rates of cast and aluminum can be a problem where gaskets are involved. Otherwise, what does your oil pressure guage read? My 86 sbc occassionally reads as high as 70 psi on startup and normally runs between 40-60 psi during normal operation and around 20 psi at idle. Otherwise, describe the process you followed for replacing the gaskets and intake manifold. Maybe someone will catch something.

Murph

MOP
03-30-2004, 09:21 PM
How much vapor is comes out of the oil fill when the engine is running with the cap off. If you have a lot coming out you may need to freshen the engine up a bit. From all the near or real over heats it may need internal work.

Phil

clayman
03-31-2004, 06:50 PM
well, the oil pressure guage is another story. Actually the last of the querks of the boat, we lick this one and I am golden. The pressure gauge seems to be backwards. At idle it reads 60-65 and under way it drops to 40-50, and when you shut down the motor it goes to 80. Could the sender be wrong? it seems opposite of what it should read.
Still waiting for my balls
Jim

MOP
03-31-2004, 07:09 PM
Just Rolling along here! Try turning on the key then ground the sender and see what it does, it should scale from 0 to 80 if it is an 80 psi gauge. I have seen a few gauges go to the top when turned off but still worked Ok. As to the funny change in oil pressure, many times when an engine is worn it the pressure will rise up under deceleration, I have had few worn out motors over the years that would jump 10-15 psi when I let off the gas and still did not knock.

Murphy
04-01-2004, 08:54 PM
Been awhile since I messed with my oil pressure sender and guage, but I remember a couple of points. First, make sure you don't use anything on the threads of the sender. It needs a good ground to the block to work right. Yes, you could have the wrong sender/guage combination. Not just any sender can be used with any guage. The ohms must be correct or you will get a bogus reading. Best bet is to call the folks who manufacture your guage and ask them to send you a replacement sender that matches your vintage of guage. If that doesn't fix it, you may have a bad guage, but my money is on the sender.

Murph

clayman
04-04-2004, 02:27 PM
Dant da da da, the $4 balls did the trick. I just ran around the lake , pissed off some neighbors, and got the temp up. Then Idled around for 15 minutes, and the temp dropped from 165 to about 155 and stayed there! Yeah! Lets go boating! I hope the other little problems don't take me two years to fix. Thanks for all your advise guys. I never would have known about the balls since it didn't have them ( I assume someone took them out ) and there was no mention of them in the manual.
Thanks , the Donzi Net always pulls through.
Jim - Seadogs

MOP
04-04-2004, 05:16 PM
So glad you finally got balls! Happy Donzi Daze!

MOP

Murphy
04-04-2004, 05:17 PM
Excellent news! That's a great looking engine.

Murph