Suzuki DT 30 overheating problems!!!! photo & video

[boatster]

Hi, I am having the darndest time trying to figure out what is going on with my motor. I have just finished rebuilding the sucker and when I stick it in a deep bucket of water to run the engine is not getting cooling. I replaced the impeller and cleared all passageways. I then openened the thermostat cover to see if water was getting to the head. It was but exhaust was shooting out the other side of the thermostat passage. As if the exhaust was some how coming from the midhousing and back up through the block. I figure that this backpressure is holding the water back from getting to the rest of the engine. Anyone have an idea whats going on? <br />Thanks

 

[phatmanmike]

Re: Suzuki DT 30 overheating problems!!!! photo & video

As if the exhaust was some how coming from the midhousing and back up through the block.

well if there is some sort of blockage, the water will take the path of least resistance, so with the thermostat cover OFF, the water will come back up.

 

[bigbrownbuku]

Re: Suzuki DT 30 overheating problems!!!! photo & video

typically if there is no water being pumped exhaust gases will get back into the block via exhaust cooling holes where the water exits the block. i would recheck your waterpump and check the key didnt shift while installing the impellor. while the gearbox is off try putting a hose on the tube with the thermo cover off and see if water is getting through.

 

[boatster]

Re: Suzuki DT 30 overheating problems!!!! photo & video

Thanks for the insight guys. Heres an update. I now can have the engine running with the thermostat cover off. The pee hole pees a storm and the warning siren shuts off. Tons of water flows out the thermostat hole. But, exhaust will come out of the thermostat side that the water is supposed to flow into.If I put the thermostat cover back on water wont come out the pee hole and the siren won't go off. Eventually the engine gets hot and I have to shut it off to not overheat. It seems to me the backpressure of the exhaust is so strong its stopping the flow of the water is this possible??? Please help I am so stumped. I took this thing apart about 5 times today, thats powerhead, lowerunit, exhaust and head, FIVE TIMES!!!! I can't for the life of me figure out why it only runs cool with the thermostat cover off. Also FYI I'm not using a thermostat. Would that be the culprit?? Thanks again.

 

[boatster]

Re: Suzuki DT 30 overheating problems!!!! photo & video

Anyone? Someone? I know someone out there knows what the problem is. Please help!!!<br /><br />One more question, could it be the plate that the water pump housing sits on is leaking air into the pump from between the plate and the lower unit housing? I did take this apart but did not put any silicon back in between. I read somewhere maybe exhaust or air is infiltrating the water pump from the exhaust tunnel in the lower unit. Maybe?

 

[boatster]

Re: Suzuki DT 30 overheating problems!!!! photo & video

Ok so I've taken a little avi of the motor idling. I've also attached a photo for those who can't view the avi. Apparently the exhaust is so strong that it is pushing the water back out the under powerhead release holes. If I open the thermostat the exhaust vents out and the water is allowed to flow around the block and thus cool the system. As you can see there is plenty of water coming out of the pump. I am stumped. <br />Heres the video http://www.porfor.com/dt30.avi <br />

 

[jim dozier]

Re: Suzuki DT 30 overheating problems!!!! photo & video

Pull the lower unit and clamp a garden hose onto the water pickup tube. Put the thermostat cover back on. Water should flow out the pee stream, exhaust relief, and prop exhaust. If it doesn't something is blocked. Look up into the bottom of the powerhead to make sure the top of the water tube isn't leaking at the place where it joins the powerhead. If everything is OK, you may want to check your water pump rebuild and that the water tube is seated correctly in the water pump. Did you remove the exhaust cover on the powerhead. You may have a hole inside the exhaust cover plate.

 

[jleus]

Re: Suzuki DT 30 overheating problems!!!! photo & video

If there is exhaust presure that can be felt at the thermostat housing I would look for a gasket leak. If you just rebuilt the motor I would rule out a crack in the block, at least I would think it would be evident at that point. The exhaust covers on the side of the motor share (the two pieces actually form) a common wall with the water jacket and may have cracked during torqing (sp) or the inner "gasket ring" may be out of place. If the outer part of the gasket is leaking it would leak to the outside of the block. That only leaves the head gasket that has a common block wall with the water jacket. Exhaust gases in the water jacket sounds like blown head gasket in my experience although that would be odd with a newly installed gasket. If it was working properly before, I would assume it is something that is not just right during the rebuild, most likely a gasket.<br /><br />I watched the "video" after the post above....that is a gasket leak...that is the only way you are going to get that kind of exhaust presure in the water jacket other than a crack in the block or covers. Only two gaskets to leak into the water jacket....exhaust cover and head.

 

[boatster]

Re: Suzuki DT 30 overheating problems!!!! photo & video

Yeah, I've already ordered a new exhaust cover gasket, water pump plate, and lower powerhead gasket. I think the exhaust gasket might have been the culprit. Also I looked at the inside of the piston #3 on the intake side and there is some overheat scoring on the intake side wall, how badly is this going to effect the performance of the piston? <br /><br />Thanks guys.

 

[jleus]

Re: Suzuki DT 30 overheating problems!!!! photo & video

The water pump "kit" is the cheapest way to go in my area....base plate, gasket, key, and impeller for about $28.00... impeller is around $21.00 by itself.<br /><br />If you go into the powerhead base (lower powerhead) gasket look hard at the mechanical seals at the pass through for the drive shaft. They are easily knocked out of place by a slightly misguided stab when installing the gear box. I think thats what let water into #3 on mine.<br /><br />I had good top end performance with a scored #3 cylinder but idle suffered and transition out of part throttle was not always pretty. It always showed good compression. Never did a leak down.<br />It depends on the scoring. It will run with it.....until it quits!! <br /><br />The 3 cylinder Suzukis are indestructable in my opinion. I have done some things with my dt25c that really make it sing.<br /> <br />Cool inflatable.

 

[boatster]

Re: Suzuki DT 30 overheating problems!!!! photo & video

Great!! Thanks Jleus. The scores on #3 you can't feel with the tip of your finger if you move over them. You can with the tip of your fingernail. They don't look bad when you look down the barrel but when you look down the exhaust port it looks bad. Well heres a photo showing the #3 cylinder.<br />

<br /><br />"cool inflatable". Thanks. Its a 13 foot avon RIB (rigid inflatable boat). I have yet to take this out on the water so my anticipation is great. Its been 2 months now since I purchased this boat. The motors been the holdup <br /><br />BTW what have you done to make your motor "sing"? I want to make my motor sing too!! <br /><br />For the scoring, would it be adviseable to use some emory cloth to smooth out the scored edges or should I just leave it be? The Suzuki manual says that lite scoring can be brought down with emory cloth. I'm not sure what to do..

 

[jleus]

Re: Suzuki DT 30 overheating problems!!!! photo & video

One of those times when a picture says NO words. Only a good machine shop that can measure it can tell you. A minor score can be a problem if it is in the exact wrong place of an out of round bore. I have not seen any noticable score that did not require boring to get rid of, boring to the next piston size that is. Find a machine shop that "does" not just "knows" outboards. I can't tell if it has been bored already....there will be an oversize mark on the piston crown if the pistons are larger than original...it will be 0.25 or 0.50 etched into the crown... those are the only two overbore sizes available from Suzuki for that motor<br /><br />Had you already put a new head gasket on it? The bottom of the sleeve on #2 and #3 look like there might have been problems.<br /><br />I have:<br />Bored 0.50 mm over<br />Cleaned up all the parting lines in the intake and exhaust.<br />Eliminated the oil injection, just something to fail. Got the brass tubes out of the intake path.<br />Stuffed the intake side of crankcase somewhat.<br />Thinned the throttle valves.<br />Fiberglass reeds.<br />Decked the block.<br />Shaved the head by .020 (compression around 140)<br />Cut the exhaust "tuner" down.<br />Relieved the exhaust at the midsection.<br />CMC PT-30 T&T. (most felt in the seat of the pants addition)<br /><br />I am turning it around 5750 rpm and it is very smooth.<br /><br />Funny thing is all that for a good old aluminum jon boat that gets used in horsepower restricted duck woods...I hate being beat!!

 

[boatster]

Re: Suzuki DT 30 overheating problems!!!! photo & video

jleus,<br /><br />how did you relieve the exhaust at the midsection? Could you elaborate on that improvement? Also what is CMC pt-30 T&T?<br /><br />I might consider ridding myself of the oil injection. I do however like to try and leave things stock. <br /><br />How did you go about shaving down the head by .o20? Did you use a mill or just some emory cloth on a flat block? <br /><br />Thanks. I'll try to take another photo of the cylinder walls later tonight.

 

[jleus]

Re: Suzuki DT 30 overheating problems!!!! photo & video

Relieved the midsection with a 1/2 inch hole on both sides, chamfered the holes really well. The holes are just above the water line at rest.<br /><br />Cook Manufacturing hydrolic tilt and trim for 30 horse and below. Yahoo will find it easily.<br /><br />With out the auto oiling I do get a little spark plug loading after extended idle, readily burns off with some throttle. I am running oil at 40:1 but use full synthetic. No plug fouling.<br /><br />Decked the block by hand on plate glass and good sandpaper. Use some spray adhesive to stick it to the glass. I asked the machine shape to remove 0.020 then decked with sandpaper on glass to be sure it was straight.

 

[boatster]

Re: Suzuki DT 30 overheating problems!!!! photo & video

Hey Jleus, thanks for all the info. BTW, why did you drill the holes in the midsection? To relieve exhaust backup? What was the reason? Thanks again. I think I'm going to have to wetsand my cylinder head flat to make sure its sealing properly. <br /><br />Adam

 

[jleus]

Re: Suzuki DT 30 overheating problems!!!! photo & video

If you can, do the mating serface on the block as well , I had a sleeve that was just slightly "proud" of the block creating a poor seal.<br /><br />The exhaust relief is for better performance out of the hole. Along with 5/32 vent holes on the prop the motor is able to spin up better from a dead stop, planing quicker with a load.

 

[Tdekubber]

Hi, I am having the darndest time trying to figure out what is going on with my motor. I have just finished rebuilding the sucker and when I stick it in a deep bucket of water to run the engine is not getting cooling. I replaced the impeller and cleared all passageways. I then openened the thermostat cover to see if water was getting to the head. It was but exhaust was shooting out the other side of the thermostat passage. As if the exhaust was some how coming from the midhousing and back up through the block. I figure that this backpressure is holding the water back from getting to the rest of the engine. Anyone have an idea whats going on? <br />Thanks

Did you ever get the problem resolved? I have a DT 30 with the exact same symptoms

 

[Tdekubber]

Hi, I am having the darndest time trying to figure out what is going on with my motor. I have just finished rebuilding the sucker and when I stick it in a deep bucket of water to run the engine is not getting cooling. I replaced the impeller and cleared all passageways. I then openened the thermostat cover to see if water was getting to the head. It was but exhaust was shooting out the other side of the thermostat passage. As if the exhaust was some how coming from the midhousing and back up through the block. I figure that this backpressure is holding the water back from getting to the rest of the engine. Anyone have an idea whats going on? <br />Thanks

Hi, I am having the darndest time trying to figure out what is going on with my motor. I have just finished rebuilding the sucker and when I stick it in a deep bucket of water to run the engine is not getting cooling. I replaced the impeller and cleared all passageways. I then openened the thermostat cover to see if water was getting to the head. It was but exhaust was shooting out the other side of the thermostat passage. As if the exhaust was some how coming from the midhousing and back up through the block. I figure that this backpressure is holding the water back from getting to the rest of the engine. Anyone have an idea whats going on? <br />Thanks

Did you get the problem resolved? My DT30 has the exact symptoms..

 

[Sea Rider]

What precisely have your rebuilt on that nice sucker motor ? No one should ever test any motor on a bucket for extended time period or will be cooling the motor with heated water which it's nuts. For that procedure need a hose that pours new water in and and some sort of water port at the lower bucket to release water out while both works at same time...

Happy Boating​