Suzuki DT30 still overheating at idle Help!!! (more photos)

[boatster]

Re: Suzuki DT30 still overheating at idle Help!!! (more photos)

Ok I took apart the motor again. I took off the exhaust cover and it looks fine. I also took off the under powerhead plate and the liquid that drips out is unburnt fuel, oil, and who knows what else. It doesn't look like water though. Anyways I am considering plugging the 2 purge holes under the powerhead plate as shown in the 2 photos below. What do you think?<br /><br />EDIT: Nevermind. I just realized those purge holes are there to cool the exhaust tubing. I don't think I should block them.<br /><br />I'm getting a leak down tester tonight. I should know more by then.

 

[jim dozier]

Re: Suzuki DT30 still overheating at idle Help!!! (more photos)

I've been loosely following your threads (2) on this problem. There's a lot of information so I may have missed something. I think it would be helpful for you to step back from this for a minute before you do more dismantling.<br />Never evaluate an overheating engine in a barrel or on the muffs, do it in real world conditions out on the water. Long before you took this engine apart multiple times you should have invested in a point and shoot laser thermometer to find out if the engine is actually overheating and if so where its hot. If its not overheating and you are getting an alarm it may be the temp sensor or the alarm. I'm not sure whether there's a problem or not with the exhaust coming out of the thermostat cover when its off if the engine foot is submerged. Backpressure on the foot would back the exhaust up against the cooling water which now is not pressurized because the thermo cover is off. If you put the thermo cover back on is there still a problem? <br /><br />As I suggested in an earlier reply you can check the flow of water through the powerhead by removing the lower unit and clamping a garden hose on the water pickup tube. You can visualize the flow and run the engine like this. Is the flow coming out of the exhaust relief holes and the prop? When you do this and run the engine does the engine overheat? If so your problem is above the pickup tube, if not the problem is below the pickup tube in the water pump.<br /><br />The causes of an overheating engine are (not in any particular order):<br />1. water pump (looks are deceptive, replace)<br />2. water tube (check the top and bottom)<br />3. thermostat (check with thermometer in hot water on a stove)<br />4. pressure relief valves<br />5. head gasket<br />6. exhaust gasket<br />7. powerhead gasket<br />8. blocked cooling channels (corrosion, old impeller bits, sand, etc.)<br />9. incorrect ignition timing (too much advance)<br />10. lean carburetor mixtures<br />11. overpropped engine (not enough rpm at WOT)<br />12. clogged inlet (crud in the inlet)<br /><br />The cause of "ghost" overheatings are:<br />1. bad temp sensor or flow sensors<br />2. bad alarms or wire shorts<br />3. inadequate muffs or insufficient water in barrels<br /><br />Lastly, I don't even know what the drain holes are for exactly but the engineers at Suzuki put them there for a reason and filling them up isn't going to fix your problem.

 

[boatster]

Re: Suzuki DT30 still overheating at idle Help!!! (more photos)

hi jimd,<br /><br />I know for certain the engine is overheating at idle. The sensors aren't lying. I captured the pee stream water in a cup and used a chemistry thermostat and it hovers around 40'-50' Celsius before the alarm goes off. This is with the lower unit attached and in a bucket of water where the level of water is clearly above the water pump housing.<br /><br />I did do what you said about the taking off the lower unit and hooking a hose directly up to the water tube. I run the motor and it runs cool with no problems and pees like a horse depending on the hose pressure. This does lead me to believe that its the lower unit but that still can't be 100% because maybe the water hose pressure is so strong it will overcome any backpressure or internal exhaust gas leaks in the head.<br /><br />At this point I am awaiting a leak down tester from my friend to check all cylinders for possible head gasket leak. I know the exhaust cover is fine. I looked at it lastnight. The gasket is sealing nicely.<br /><br />I also tore down the lower unit lastnight. I am going to put it back together carefully. There is a secondary inlet that feeds into the main water inlet on the lower unit housing. I wonder if it could be sucking air from the exhaust casting or from outside since it connects to the main inlet via a lower unit plate that mounts on top of the lower unit housing. Supposedly only silicone is used to seal the mating surface of the plate and lower unit housing. As far as the water pump is concerned, I replaced the gasket, the pressure plate, impeller, but not the water pump housing oil seal. I've inspected it, and it looks ok to me. The grommet that attaches to the water pump tube connects snug too. <br /><br />When I open the thermo cover, it seems plenty of water is being pumped from the lower unit so I am kinda stumped. Maybe alot of water but very little water pressure? I dunno whats going on here.<br /><br />

"Backpressure on the foot would back the exhaust up against the cooling water which now is not pressurized because the thermo cover is off. If you put the thermo cover back on is there still a problem? "

Jimd, that I believe is the problem, backpressure. Yes, when I put the thermo cover back on I can tell that the backpressure is winning over the cooling water since the pee stream is strong when the thermo is closed. Once the thermo opens the pee stream starts to pulse with the exhaust and starts weakening, thinning, and spitting, then the alarm goes off. This is with the lower unit in a bucket (no muffs), at idle ~800 rpms. Also the pee is definitely not luke warm.<br /><br />Adam

 

[boatster]

Re: Suzuki DT30 still overheating at idle Help!!! (more photos)

Ok,<br /><br />so this afternoon I put everything back together and ran the motor in a bucket with the lower unit on. The water is flowing and the alarm is not going off. I took temp readings of the pee stream with a cup and chemistry thermometer and I'm getting 40' Celsius (104' farenheit). This is the pee stream mind you. I put my hand on the top of the exhaust cover and I can hold my hand there no problem. The head feels the same. I imagine the block temp is somewhere near 40' Celsius as well. Is this cool enough? Should the pee stream be cool, luke warm < 40' celsius, or warm-hot approx 40' celsius? A new phenomenon I experience is that air will gurgle up from the prop intermittently. This tells me that the water pressure is now strong enough to push the exhaust back. When it gurgles, the water out the pee stream drops a few degrees.

 

[jleus]

Re: Suzuki DT30 still overheating at idle Help!!! (more photos)

My books say thermostat starts to open at 118-126 degrees F.<br /><br />From your post I understand the cooling is working as it should?

 

[boatster]

Re: Suzuki DT30 still overheating at idle Help!!! (more photos)

Hi jleus,<br /><br />I'm not sure. Everything does look ok. I don't really have any experience with the motor running cool as I recently purchased this motor. YOu know I reassembled the lower unit and water pump. I also "decked" the under powerhead plate too. It looks like this time around I've taken extra care to everything I've done and its shown a major improvement. How warm/hot does your pee stream come out of the motor when its warmed up idling? Do you have an intermittent gurgling from the prop shaft of air while at idle or is it constant(while in bucket)? I wish I could see what a properly running Suzuki 30 idles like.<br /><br />BTW I also performed a leakdown test and all three heads have the same even slow leakdown. Very good news. No leak in the head. This must really imply that the water pump is/was the culprit.

 

[jafa]

Re: Suzuki DT30 still overheating at idle Help!!! (more photos)

Hi Adam<br />My thermostat does have the temp stamped on it (deg cel) , its also comes in a 40deg and 50 deg variety depending on your local conditions. What did you do different this time to get it going. Has the tap water temp suddenly taken a drop ?

 

[jim dozier]

Re: Suzuki DT30 still overheating at idle Help!!! (more photos)

The pee stream temp is not a good indicator of engine temp. The pee stream is an indicator stream coming off the cylinder jacket (at least it is on my 3 cylinder DT85) and its water hasn't gone through the cylinder head yet so the temps are not reflective of the maximum water temp exiting the cylinder head. As I said in the previous post evaluating the engine temp without a temp gage or laser thermometer while its running in a barrel is not a good idea. Where is the water level in your bucket or barrel in relation to the position of the water pump? The water pump must be submerged as the pump does not suck water very well it must push it. The water needs to be well above the level of the water pump in the lower unit. I am not totally convinced your engine is overheating. I would hate to think that you have gone through all of this for nothing. <br /><br />Put the engine in the lake or ocean and you should be able to keep your hand on the cylinder area just behind the flywheel but before the cylinder head without burning your hand (the cylinder head will burn you). The acutal temp of this cylinder area should be less than ~163 degrees F. Cylinder head temps will run up to about~190-200 degrees F at WOT. For less than $50 you can buy a point and shoot infrared thermometer at Radio Shack and confirm if you have a problem. Temp sensors can go bad and if the alarm is going off and your engine isn't overheating you need to address the temp sensor.<br /><br />You said "I know for certain the engine is overheating at idle. The sensors aren't lying. I captured the pee stream water in a cup and used a chemistry thermostat and it hovers around 40'-50' Celsius before the alarm goes off. This is with the lower unit attached and in a bucket of water where the level of water is clearly above the water pump housing."<br /><br />How do you know for certain? Temporarily remove the thermostat and replace the thermostat cover. Does water exit the exhaust relief hole at the top of the leg? If not there is a problem with flow. If water is coming out of the exhaust leg and the engine alarm is going off I would suspect the alarm. You really need to quantify the temp of this engine before you go any further. Guessing engine temps is not good.

 

[boatster]

Re: Suzuki DT30 still overheating at idle Help!!! (more photos)

Rockhopper,<br /><br />I disassembled the lower unit and put a thick marine silicone between the lower unit plate and the lower unit housing (as told by my manual). I also sanded flat the under powerhead mounting plate. Apparently it was bowed a little. Enough where the inlet from the tube may possibly leak past the under powerhead gasket. I also simply blew alot of high pressure air through the block for safe measure. Oh, I also decreased the oil pump flow (to within spec). The previous owner had cranked up the oil pump flow significantly.<br /><br />Jimd,<br /><br />If the pee hasn't yet gone through the head yet that make me worry even more. I'll have to look into gettting this thermometer you mention. As far as the water pump being submerged, I have the water level clearly 3" over the top of where the water pump is. I would imagine that would be enough?<br /><br />Come to think of it, I'll get this thermometer you mention. It uses an infrared you say?<br /><br />In any case water is spitting out the exhaust relief hole at the top of the leg and the alarm hasn't gone off yesterday. <br /><br />Can you please answer this though, Does exhaust come out of the prop either intermittently or constantly while the engine is idling in a bucket of water? Mine does intermittently. I really need to know this info as it shows the water pump is winning over the backpressure of the exhaust.

 

[jim dozier]

Re: Suzuki DT30 still overheating at idle Help!!! (more photos)

Water should exit the exhaust relief only after the thermostat opens (or all the time if the thermostat is temporarily removed). It should comes out in sort of a sprlow (cross between a spray and a flow) because it is mixed with exhaust. It isn't a stream like the pee stream which is only water. It should be fairly consistent though.

 

[bossee]

Re: Suzuki DT30 still overheating at idle Help!!! (more photos)

Hi,<br />Have You tested the "water level" (flow) sensor (= overheat sensor) switch with an ohm meter so see if it is OK?<br /><br />I had a Suzuki DT 65 (1991) before and I had overheat alarm problems with that outboard. It turned out the water flow sensor was defect.<br /><br />Good luck!

 

[jim dozier]

Re: Suzuki DT30 still overheating at idle Help!!! (more photos)

What year is this engine. I am looking at the parts blowup on www.brownspoint.com and it shows a gasket beneath water pump panel plate. I could be wrong but it is generally not a good idea to use silicone sealant where it can get into the water pump (it will often squish into the pump area when you clamp down the bolts. That engine is very similar in design to my DT85 which has a paper gasket beneath the water pump plate. The only place I used silicone was on the bridge on the lower unit between the pump and the exhaust area (applied after the water pump was installed) when I sealed the lower unit back on. Also, make sure you have installed the plate underneath the impeller with the proper side up, on some of these engines it is possible to install it upside down which restricts the inlet to the water pump.<br /><br />Bo the parts diagram doesn't show a flow sensor on the DT30, just a heat sensor.

 

[boatster]

Re: Suzuki DT30 still overheating at idle Help!!! (more photos)

Hi jimd,<br /><br />its an 89 dt30c. Actually there is a flow sensor on my motor in the head. The silicon is used under the plate from the secondary inlet under the cavitation plate. The plate I'm mentioning is not the under pump plate. Its the plate that sits on top of the lower unit. My manual shows that silicon needs to put down there to make a seal for the secondary inlet. I think what your describing is the same as me. For the water pump theres the gasket, the pressure plate then the impeller, then the water pump housing. No silicon there. <br /><br />Anyways I took the boat out on the water today and it runs great. No overheating. Only when I pulled into the dock and at the end of the day, the engine was idling down and the buzzer went off. I guess its because I was WOT for a while then went immediately to idle so the cooling probably could not keep up. It seems the cooling is a little on the hot side while idling but while running the pump cools the motor plenty. Other than that everything looks pretty good from here. Carbs need to be adjusted but thats an easy task.<br /><br />Thanks all you guys for your help, jleus, rockhopper, jimd, and everyone else who popped in a suggestion or two. I only hope I can return some helpful advice in the future to pass on what little I know. <br /><br />Adam

 

[jafa]

Re: Suzuki DT30 still overheating at idle Help!!! (more photos)

Adam<br />Can you post a pic of your plugs after a run , would be interested to see what they look like. I've kinda got the opposite problem maybe running too cool or over-oiled hence dirty plugs..

 

[boatster]

Re: Suzuki DT30 still overheating at idle Help!!! (more photos)

Rockhopper,<br />the spark plugs? Sure. I'll get the photo up tomorrow. Its 12:52 am and I'm gonna hit the sac.<br />Hey could you do me a favor? Can you tell me roughly how hot the pee stream is from your motor at idle? Also does it bubble air from the foot constantly or intermittently? I am going to post a video of my motor idling today in the water. Can you tell me if this looks overall healthy? I'll get that photo of the plugs ASAP. Thanks.<br /> http://www.porfor.com/idle.avi <br />Adam

 

[boatster]

Re: Suzuki DT30 still overheating at idle Help!!! (more photos)

Ok, <br /> here is the best photo I could take up close of the plugs. A little blurry. If you want I can take a better photo later on. <br />Cylinder 1 on the right.<br />

<br /><br />As of right now I am running a little premix in the gas as well as a little rich oil in the oil mix pump so the plugs are definitley too wet. That will soon be fine tuned.<br /><br />EDIT: Hey Rockhopper. I tried taking several more photos tonight. No luck my camera won't zoom in that close and take a clear photo. Sorry if that photo doesn't help. Maybe I'll try again in the daytime this weekend.

 

[jafa]

Re: Suzuki DT30 still overheating at idle Help!!! (more photos)

Possibly try setting the camera to macro mode ?<br />Anyway I downloaded the video and ran it several times and I can safely say that yours is exactly the same as mine right down to the stength of pee stream and splatter of the exhaust relief , replaced my impeller last month. Shame it was a bit windy. Gas discharge from the hub is the same , so at the risk of being contradicted , I cant see anything wrong with it. Looking at your plugs , are you useing two different types as one seems to be silver , the others bronze ?. Your motor uses b7hs10's which are silver and hotter than the b8hs10 which go in my dt40. I'm lead to believe that the difference in plug temperature from one range to another can be 100deg F.on the plug tip, hence raising cylinder temp although i doubt it raises the cylinder temp that much. Is that where your temp sensor is located ?<br />FYI yours is just a fouled as mine and i've got textbook compression. I'm currently finishing up a gallon of valvoline but will try merc to see if it improves. Speaking of oil your sure its a temp alarm not an oil low alarm.<br />Whilst we are on the electrics , I couldn't see you posted a year, but dt30's 92-99 electric start , had two heat sensors , from the cdi a v?/white to the cylinder temp sensor and a green/red to a heat sensor blue/black for the oil , all go to ground on activation. I'm not sure about this heat sensor as I cant see a pic of one anywhere. My clymer states an switch activation at 207-217f deactivate at 181-207f and 56-84 ohms at 77f for the cylinder temp sensor. Try triggering an alarm and then unplug the sensors and confirm the sensor triggering it.<br />Ooopss completely missed your question. The pee stream is some 25f warmer than the input , you wouldnt want to have a shower in it. The exhaust relief some 50f hotter then input ,not measured.

 

[boatster]

Re: Suzuki DT30 still overheating at idle Help!!! (more photos)

Rockhopper,<br /><br />I didn't even notice that the plugs are different colors. I'll go check to reconfirm what model they are. I'll also go and try to take clearer photos of the plugs in the daylight. <br /><br />As far as the pee stream is concerned, the pee coming out of the motor is around 45'C. The water coming in is pretty much cold. So we have some kind of discrepancy there between yours and mine. In my other post I've already made light of my motor overheating at idle. Thats when the buzzer is going off. Let me try and retake those photos of the plugs for you.<br /><br />EDIT: Ok rockhopper. I took a much better photo of the plugs. They might be a little dark but I think you can see everything. I just replace the first blurry photo that I posted above. If you don't see a new photo try hitting refresh on your browser.

 

[jafa]

Re: Suzuki DT30 still overheating at idle Help!!! (more photos)

My input temp is a bit colder as its spring down here (NZ) and local water temps about 13 deg. The overheat alarm is 100'c so even allowing for that yours is still a bit hotter. Heres a thought, try wrapping ptfe tape around the feeder pipe where in enters the grommet on the pump, increase the diameter a bit and ensure its seals. Looking at the pic , perhaps somebody JimD could comment but they dont look like they are running hot. Too rich and overoiled , maybe but not lean. Thinking of your output temp its probably fine. Shows the thermostat is opening and holding the temp as long as it doesnt exceed 50 , assume thats your thermostat temp (is there a 40deg version available).

 

[boatster]

Re: Suzuki DT30 still overheating at idle Help!!! (more photos)

I just wanted to give an update on my DT30. I have since rebuilt the motor with new pistons and rings. I did not get the block bored but rather just rehoned. Everything has been great ever since. I have already broken the motor in and have been using it quite a bit. The motor has loads more power and runs smoothly. It no longer overheats either. Thanks everyone for all the good advice. It seems in the end new rings were the call even before I scored the original pistons to hell.