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Dozer

Overheating at high speed

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I just installed a new Simrad GO9 unit that came with a TotalScan Transducer – it’s fairly large as far as transducers go. According to the installation guide, you can install it in a few different places within the transom. So, I decided to install it at the lowest recommended spot, which is having the bottom of the transducer inline with the bottom of the boat. I used a level to make sure it was setup correctly and installed the bracket to the starboard side of the drain plug, and slightly above it to keep the bottom of the transducer leveled with the bottom of the boat.

Took the boat out and went for a nice run, about 5 or 6 miles cruising at about 30 MPH the engines (yes both) started overheating. The first one to overheat was the starboard engine with the alarm going off, so I automatically shut it off.

At first, I couldn’t figure out why this was happening, and then realized the only thing I had changed on the boat was the installation of the transducer. When you cruise at low speeds (about 5MPH) or just let the engines idle they very quickly cool down to normal temperatures.

So, is it possible that the transducer is causing that much turbulence or interference to affect the water flow into the cooling holes?

Later on, the day I was able to tilt the transducer up, but when I installed it, I failed to leave enough slack on the wire to tilt it full 90 degrees, I was only able to tilt it about 45 degrees. Set out for another run, at about 35mph and within about 4 maybe 5 miles the engines started overheating again, with the starboard engine being the first to overheat – as I mentioned above the Transducer is closer to the starboard engine (it’s installed on the Starboard side of the drain plug) …I just can’t imagine that the transducer would cause that much disruption.

When I flush the engines, either with the “ears” on the lower unit, or the direct flush into the water pump the engines DO NOT overheat.

Usually I leave the boat parked at the marina and only bring it to the house in the off season, but I brought it home so that I can maybe move the transducer up from it’s current location about 10”, but I would like to hear from someone if they think it’s the transducer causing overheating before I start putting more holes on the transom for the new bracket location.

 

Thanks for any advice.

 

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Did you do what I did ?    I backed the drive into some of the sandy  bottom. Started doing almost the same thing in a short time after that. Check the drives slotted water inlets for sucked in stuff.

Possible ?  Right after installation ?   Simply release the transducer from the bracket & tie it up above the water. So it does / can not have any effect.

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 Reread your post . Is the transducer on the OUTSIDE ?

Or is it in a  hole in the keel  ?

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When you flush your engines you are forcing water into the engines and the engines are not the pressure of powering the boat.

I dont think your transducer has anything to do with it.

You could put a heat gun on them to make sure they are overheating, not just a faulty sensor.

It is odd for it to happen to both engines at once.

Check for blockages

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How hard would it be to remove the transducer temporary and do a test ride? At least then you will know for sure.  W

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9 hours ago, jeffk said:

 

Check for blockages

Or a new transducer...It's the only thing that has changed.

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doubtful its the transducer.  Either your sensors are bad, something is clogged or your impellers are going bad.  Could also mean your thermostats are going bad.  Thermos and impellers are easy checks.

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Its odd that both engines would overheat at the same time considering all possible causes given the duplication of the cooling systems; two thermostats, two impellers, two pick up hoses, two temp sensors, ect.... Seems very weird the timing of a failure on both engines at the same time. I don't see how a pick up could disrupt water flow to one, yet alone two lower unit water pick ups.

I would remove the transducer and run again, checking the actual temps with a IR temp gun.

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I'm going to remove the transducer from the bracket -- and zip tie it to the swim platform brace and see what happens this coming weekend when I take it out again.

This is a large transducer, compared to many others out there, this thing is easily 3-4 times larger than most transducers I have seen on other boats.

Ok, so I'm hopping the transducer is the problem...but I have my doubts/ If it's not then where else should I start looking?
I have checked for blockages, and I have not backed into the sand or low grass areas.
Thanks

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Most likely cause is impeller failure on both engines. Is there any possibility that the engines got started, and pumps ran dry even for an instant while the boat was out of the water? Another possibility is you ran into a floating large trash bag that starved the pumps just long enough to trash both impellers. A quick check is to remove the drive belt and turn the raw water pump impeller by hand in the same direction as engine rotation. You should feel constant, smooth resistance kinda like a small rubber squeeze on a windshield. . If it feels notchy or has an area of drag and an area of free rotation the impeller is trash.  W

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I suspect it's electricity issue since you just had transducer installed. Did you check your fuses or circuit breakers? They might disconnect your water pump cable or caused water pump doesn't have enough power to drive. 

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2 minutes ago, Patrick Kim said:

I suspect it's electricity issue since you just had transducer installed. Did you check your fuses or circuit breakers? They might disconnect your water pump cable or caused water pump doesn't have enough power to drive. 

Water pump is belt driven off of the engine. Strictly mechanical.  W

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Here is an update and some more questions on trying to solve this issue.

So, I moved the transducer out of the way, and that did not help - same issues.

Ordered and installed new Thermostat and Impeller kits -- The old thermostats opened at 160 Degrees when I placed them in pot of hot water, which tells me they were working correctly, but since I had new gaskets and new thermostats I installed them.

Took the boat out, and the engines still overheat, but don't seem like as much as before.  The alarms did not go off, but  I think I was being too cautious.

Have not tested after replacing the impellors, but the old impellors looked great, so I don't think this will make any difference.

So now here is my question, in regard to thru hull raw water intake

Currently I have a fresh water flush kit installed that "Ts" in the raw water hose (red one) right before the water pump. I also have TWO seacocks -- one for the Generator and one for the A/C.

Would it help if I installed a "T" in each of the current seacocks (Generator and A/C) and plumbed to the "T" where the current fresh water flush kit connects on the red hose -- Temporarily keep the flush kit hose disconnected to see if this extra volume of water will help keep the motors cool.

Here is my logic (if it makes sense) -- From what I understand, the raw water line from the Bravo 3 outdrive is a 5/8 diameter, that then feeds into the 1 1/4 RED hose to the water pump. Over time the raw water hose from the outdrive may collapse and restrict the flow due to the higher demand from the water pump when running at the higher speeds. By adding the extra supply from the seacocks, I would prevent the outdrive hose from collapsing and water would still flow from the outdrive to cool it off.

I don’t use the Generator or the A/C when the engines are running. What do you all think?

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Could the motor be sucking air at the flush kit, and thus losing prime at high speed?  Just a little air would have things not working correctly.  Take that out of the system (which means it is closest to the original factory condition) and then try.  I would do this prior to making a "Frankenstein solution" to a problem you shouldn't have if everything is working correctly.

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9 minutes ago, Jjlai724 said:

Have you inspected your risers lately?

That's what I was thinking.......

 

 

.

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35 minutes ago, chasingmemories said:

Could the motor be sucking air at the flush kit, and thus losing prime at high speed?  Just a little air would have things not working correctly.  Take that out of the system (which means it is closest to the original factory condition) and then try.  I would do this prior to making a "Frankenstein solution" to a problem you shouldn't have if everything is working correctly.

This is the reason I post in here, good point - I will take out or pinch the fresh water inlet hose and see what happens

7 minutes ago, Jjlai724 said:

Have you inspected your risers lately?

I have not inspected them, but using a Laser infrared Thermometer the risers seem to be operating at normal temperatures without any hotspots -- that I can tell

But I guess that will be my next step once I try it without the flush system being connected.

 

Thank you all for the suggestions, if anyone can think of anything else, let me know

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The risers may not be allowing enough water into the engine.  The engine will get hot before the risers if there isn't enough water.  

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20 hours ago, Dozer said:

Here is an update and some more questions on trying to solve this issue.

 

So, I moved the transducer out of the way, and that did not help - same issues.

 

Ordered and installed new Thermostat and Impeller kits -- The old thermostats opened at 160 Degrees when I placed them in pot of hot water, which tells me they were working correctly, but since I had new gaskets and new thermostats I installed them.

 

Took the boat out, and the engines still overheat, but don't seem like as much as before.  The alarms did not go off, but  I think I was being too cautious.

 

Have not tested after replacing the impellors, but the old impellors looked great, so I don't think this will make any difference.

 

So now here is my question, in regard to thru hull raw water intake

 

Currently I have a fresh water flush kit installed that "Ts" in the raw water hose (red one) right before the water pump. I also have TWO seacocks -- one for the Generator and one for the A/C.

 

Would it help if I installed a "T" in each of the current seacocks (Generator and A/C) and plumbed to the "T" where the current fresh water flush kit connects on the red hose -- Temporarily keep the flush kit hose disconnected to see if this extra volume of water will help keep the motors cool.

 

Here is my logic (if it makes sense) -- From what I understand, the raw water line from the Bravo 3 outdrive is a 5/8 diameter, that then feeds into the 1 1/4 RED hose to the water pump. Over time the raw water hose from the outdrive may collapse and restrict the flow due to the higher demand from the water pump when running at the higher speeds. By adding the extra supply from the seacocks, I would prevent the outdrive hose from collapsing and water would still flow from the outdrive to cool it off.

 

I don’t use the Generator or the A/C when the engines are running. What do you all think?

 

Never saw an issue with the Bravo suction hose, however there is an issue with the hose barb that connects the water transfer hose from the gimbel to the transom plate. They corrode and over time the opening will reduce in diameter. Before I added another water source, I'd raise the drive fully, and remove the transfer hose from the transom plate and take a look at the hose barb. Also as mentioned, check the flush kit to be sure it's not sucking air. You said that the old impellers looked fine. How did the pump housing internals look?.  Shared pick-up could cause the AC to back draw the engine supply stream causing the condenser cooling pump to become air bound. Likely the same thing will happen when you start the engine as the raw water pump would back suck the condenser as water seeks it's own level and flow will take the path of least resistance. Check valves would solve that issue but they restrict flow and your introducing another service item. If you are intent on going that route, then add another thru-hull and cap off the feed from the transom.. W

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When you cruise at low speeds (about 5MPH) or just let the engines idle they very quickly cool down to normal temperatures.

 

Usually means clogged elbows, guessing your raw water cooled. Try this.

With the motor off, check the large hose at the circ pump feel the rubber flex/ softness. Start engine , go to 2000 rpm and check hose to see if its rock hard. YES= clogged elbows and or manifolds

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I am having a similar issue as Dozer.  I just recently had twin volvo penta 350's replaced in my 285ssi.  New motors, new exhaust manifolds, and after about 8-10 minutes at 3000-3500 rpm i get an alarm on the starboard engine.  IR gun on both engines show identical temps on block and exhaust manifolds within normal.  Temp on starboard thermostat housing was significantly higher than housing on Port engine.  Impellers have been checked on both engines and thermostat was replaced on starboard engine.  Still overheating after 8-10 minutes at 3000 rpm.  Thinking it may be sucking air like chasingmemories mentioned, but how do I test that?

 

http://s1079.photobucket.com/user/cjhansen93/media/20180430_103646_zpsk8ih62jz.jpg.html?filters[user]=147222429&filters[recent]=1&sort=1&o=0

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After replacing thermostats and impellers I have come to the conclusion that it's the risers and manifolds.

I got a hold of the previous owner, and he said the owner previous to him replace them in 2013 -- so I think their are at the end of their life.

So now I need help in figuring out which manifolds and risers -- I have been looking and I'm not sure which ones are correct for my boat.

How do you figure out which part numbers are correct?
 

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Used boats may not have the original engines.  Or even the correct parts on it. Crummy servicing & repairs to save money.

Block number is needed. Check cylinder heads  to see if they agree with the block number. Great mechanics can create a parts nightmare.

 

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I guess I forgot to post an update here...my bad, I don't like to read a topic that leaves out how the issue was resolved.

So I just ordered new Exhaust manifolds and risers with spacers.

When I took off the old parts, you could see the water jacket passageways were restricted due to the rust, and being 5 years old. Also when I took the brass caps from the bottom of the manifolds, they were full of old rusty metal shavings and other very small debris that completely clogged up the passageways. It still allowed some water to flow, kind of like water slows through sand. So when we increased speed the engines would heat up, at lower speeds it was able to keep up with the cooling.
The very first time I had the overheating issue, it happened to the Strd engine, after replacing impellors and thermostats, then both engines started heating up quicker than before and at the same time. I attributed this to a lot of crud that was stuck to the cooling hoses. When I changed the impellors I moved, bent and squeezed the hoses...this caused more debris to accumulate in the water jackets, which caused more water restrictions.

After installing all the new parts, the Strd engine operated great, but the Port still had overheating issues. Turns out the new thermostat I initially installed, went bad. Replaced it and fixed the issue.

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