08 DF300Z overheating issue

[HalesMarineServices]

I just bought a 08 Proline 32 with 2008 DF300Z and it has sat for 3 years and has only been run a few times. These engines have 34-35 hours on them. I just finished putting new water pumps, t stats, poppet valves, new water tubes and grommets, tune ups, oil changes, all filters, new cylinder head temp an exhaust manifold temp sensors. That being said, I am still having the exact same overheat issue it had from when I purchased the boat. I have Suzuki diagnostic software and cable so I can see the temp rising on the monitor. It takes about 2-3 minutes of running at 2000 rpm's to set overheat alarm or about 6-7 minuted at idle or just above idle. When run at 2000 rpm's it sets a gradient alarm. When run at idle it set cyl temp alarm. Temp reaches 210-220 pretty quickly and I am not getting consistent tell tale stream from either engine. I have run descaler mixture through both engines repeatedly with no change. Has anyone ever had this issue? I have been doing marine service for a long time but I am stumped where to look next. Any input is appreciated.

[Harper]

Honestly, you, as a service tech, probably have more general outboard knowledge than most of us on the forum, as we're mostly just end users, boaters with what knowledge we can glean from our own experience and that of other members. But I can offer this from all my shadetree auto wrenching over the years. When I see unexplained overheat conditions, and have eliminated the cooling system itself, I start looking at timing, fuel mixture, or other reasons for detonation, or for exhaust obstructions. I think your diagnostics would pick up the first two easily, but is there any chance that the exhaust is somehow obstructed?

The other thing that I find strange ... you refer to "these" having 34-35 hours, and everything done is referred to in the plural, indicating that you are talking about 2 (or 3) engines. Strange that they have the exact same problem.

[HalesMarineServices]

Thanks Mike. I have also ruled out exhaust obstruction. I pulled the t stats and slowed down the overheat time but overheat is still the end result. Yes BOTH engines display the same exact symptoms. Timing is dead on as well as fuel trim and O2 sensor info. I'm not a Suzuki guy but the same pricapals should apply. The issue is water flow I believe because when I pull the t stats and crank engine there is very little water flow at top of head. Water pressure sensor reads 13 psi but water just trickles out at top of engine. I cant figure out where the breakdown is between the waterpump and the t stat housing.

[Harper]

Man, it's hard to imagine any appreciable scale buildup in the water jackets of engines with only 35 hours, regardless of how long they sat idle. I don't see where you state that you had run the engines at all prior to the R&R of the parts. So, have to ask if maybe the water tube seals or O-rings might have slipped out of place during reassembly. And not to insult, since I'm sure you know to replace the impellers with vanes correctly oriented, but I always mention that to forum members who experience overheat problems after a water pump rebuild.

I don't know anything about the 300, so I'm just throwing these things out there. I see that the parts diagram shows bushings each end of the water tube, so it seems unlikely that they would slip out of place as easily as, say, an O-ring. I guess the only other seal that I see of note is the water return seal on the engine holder, but you probably didn't disturb that anyway.

Still awfully strange that both have the same fault. I won't show my ignorance by posting anymore but I do wish you luck. Keep us up on your findings. I hope for more informed responses from others.

Edit .... How about something obstructing hose #12 in the parts diagram labeled "thermostat"? It runs from the engine holder cover to the three way and into the heads. Could the hose interior be broken down, causing an obstruction? Okay, I'm out of ideas ....I'm outa here!

[artdf175]

Hello
An 08 or 2-08's with that few hours?
Not run for 3 years that puts it back to 2012 what happened the first four years?
Are you really sure on the hours? Sorry for the long preamble

Now having said that my '06 had 500 hours on it -just had it rebuilt at about 20 hours after work was done all of a sudden the overheat alarm sounded but only at idle at about 1500-2000 rpm it put enough water through the head to cool it off
Did you check the bypass valve? That is a known problem
Can I assume there is a hose flush port on the port side ?
I understand the bolts are touchy in like breaking off but it would be an important inspection point
Reason my mechanic spent hours checking everything but could not find where the water was going - behind that cover plate was about s 1 inch hole that was dumping fresh water back into the exhaust port on the back side
Worst yet - that is the oil pan inside the oil pan between water and exhaust was another hole- you don't find until the power head off
There is a couple of things most folks have not run into

Art

[HalesMarineServices]

Mike I have changed all of the grommets and it had the same symptoms before I worked on them. Art I am positive about the hours. Scan of ECM confirmed and I bought from a friend in bad health. Boat sat in harbor for three years and only moved twice. I bought 2 identical hulls, 1 is 08 Proline 32 with DF300's and the other is a 05 Proline 32 with Honda Bf250's. I may be pulling powerhead soon to inspect everything anyway. Thanks everyone.

[bezerk]

are you in the water or on hose. on hose very common to over heat ,must be 5/8 hose and no more then 50' with good water pressure . or run in bucket with water well above water pump .

[artdf175]

that is really amazing you could have found motors with so few hours. mine was a year and half old with 25 hours.. unfortunately the guy who I purchased the boat/motor from was over his head and I am now confident that he was given no instructions on how to break the motor in properly.. I just didn't realize until 2 years ago how oil it was burning until I started doing 10 hour tuna trips,, and then the first of the year finally found a mechanic I could trust to rebuild it..
I can agree with bezerk on the water hose.. actually I am thinking the manual tells you not to run it on a hose..
I also learned that on my 175 you need to use two sets of muffs.. one goes over the screened intake.. and the other over a set of holes in to the front of the screened intake, or you are just sucking air into the engine..
it maybe one reason there are a number of post about overheating problems that are fixed by putting it in a barrel or back in the lake/river to test run it..

Good luck on your project.. and post back what you find out
Art

[HalesMarineServices]

Thanks bezerk...I was going to try the barrel method before I go any further just to be sure. Maybe that will fix it.

Art I could not pass up this deal. I got both boats for 80K! They are both in great shape except for some cosmetics and from sitting but I will whip them back into shape soon. The 08 model Proline 32 is supposed to run 53 mph!!! Not that I want to run it that hard but would be nice if your running from a storm.
Thanks for every ones input. I will update as soon as I can.

[HalesMarineServices]

pic of boats

Here is the boat I am referring to.

[HalesMarineServices]

Pic of boat

Here is the 05 Proline 32

[artdf175]

very nice boat..
((just lacks a few rod holders!!))

[Jyoung]

This may seem trivial, but did you use Suzuki water pumps or aftermarket parts like Sierra. I replaced mine with a Sierra and it would not pump enough to cool my 2015 DF250. If you replaced the water pressure control valve just above the lower unit, I would have guessed that to be an issue. I have been working on an over heat issue at idle for a couple months now and I think I finally figured out all of the circumstances causing it. Mine only overheats at idle and it is on the exhaust temp sensor.