Overheating issue

C

Colleeng

New Member
Mar 6, 2021
10
Boat Info
2007 310 searay Sundancer twin 5.7 v drive motors
Engines
Twin 5.7 v drive
Hello all so happy to have found this group and hope someone here has had these same issues and can help. I have a 2007 searay Sundance 310 v drive twin 5.7 motors. The starboard engine alarm keeps going off saying overheating and won’t get over 1 psi. We have replaced sensors, thermostats both raw water pumps and hoses. Opened sea cock and cleared out anything in pipe to no avail. Has anyone else had this issue. Please please help us.
 
Were the old impellers missing any pieces?

Did you replace the pressure sensors with Mercruiser parts or cheap aftermarket parts?

If the sensor is working properly and still reporting low pressure, you may have insufficient water supply to the pump or a blockage between the pump output and the sensor location.

Do you still have a low pressure warning?

How old are the risers, have they been removed and inspected for blockage?
 
Both great answers guys thank you. The impellers were broken for sure as we replaced both sides . Not sure about the risers as we just bought this boat a month ago. It sat on lift for three years but only 160 hrs on motors. Very frustrated but will def appreciate any help we can get.
 
Yes all merc parts and yes still getting low pressure warning
 
Has anyone used Sierra manifolds are they decent or should I stick with merc ?
 
Hi guys well finally got overheating issue figured out after replacing sensors, thermostats raw water pumps and manifolds and risers thanks for all your suggestions. Now with that said we took boat out yesterday no alarms but can’t get over 17 mph and psi on starboard motor is at 3.4 port is 10. Does anyone know what normal psi should be? It seemed that when I throttle it doesn’t seem to go any faster past 1/3 throttle to full throttle. I appreciate any help. By the way we used all merc parts if you need to know that.
 
DOES anyone know what PITOT FAULT MEANS??
 
Espos4 said:
If you haven’t done so already, you’ll need to track down the missing impeller pieces. They are a definite source of a “low pressure” problem.
Click to expand...
Thanks so much. Do you happen to know what PITOT fault means ?
 
A PITOT sensor is an item on an outdrive equipped drive train that uses water pressure to drive the speedometer needle.

Your V-drives don’t have a PITOT so that is why the fault is there.
 
Espos4 said:
A PITOT sensor is an item on an outdrive equipped drive train that uses water pressure to drive the speedometer needle.

Your V-drives don’t have a PITOT so that is why the fault is there.
Click to expand...
That’s a great answer. Interestingly enoughour speedometer isn’t working either and we cannot get over 18-19 mph .. we have replaced raw water pumps, sensors, manifolds and risers, thermostats , spark plugs . At full throttle can’t get over 3200 x 3800 rpm. Psi’s are 3.4 then the port is 10 ? There is a slight pull on the starboard engine at full throttle as well.
 
Colleeng said:
That’s a great answer. Interestingly enoughour speedometer isn’t working either and we cannot get over 18-19 mph .. we have replaced raw water pumps, sensors, manifolds and risers, thermostats , spark plugs . At full throttle can’t get over 3200 x 3800 rpm. Psi’s are 3.4 then the port is 10 ? There is a slight pull on the starboard engine at full throttle as well.
Click to expand...
You say that you just bought the boat. Did you have a survey and sea trial performed before purchase?
Did it ever achieve the rated WOT RPM?

A dirty bottom can cause this. If the bottom is clean, I would do a proper compression test and post the results here.
 
Hello all. I’m having troubles with me 5.7 350 horse motor at high throttle with low rpm on starboard side.. I have replaced manifolds and riser, raw water pumps, spark plugs, rotor, wires, ignition coil can anyone help me please?
 
Many many many many many different things could cause your issue.

The best thing that you can do if you want help on this forum is to provide as much info as possible, you can start by rereading post #13.
A fuel pressure test is also A good idea.

I’m not trying to be a wise ass, just trying to help.
 
Last edited:
As @Espos4 pointed out your asking what seems like simple question, "why" but you need to provide specific details about performance issues.

What are the exact models (get the model and serial numbers off the engines) so we can look up the detailed parts lists and manuals for you.
As asked before:
Did you have a survey and sea trial performed before purchase? When?
Has it ever been able to reach WOT?
WOT on both engines?
Currently there are NO alarms, or warning codes?
How old is the fuel in the tanks?
When was the fuel filters last changed? Primary and secondary filters?

If NEITHER engine can reach close to WOT the chances of both engines having different problems at the same time is nil.
If one engine is having problems the other is doing all the work so it wont reach WOT but should be considerably high then the "weak" engine.

Be very specific with any response, we dont know what you mean if you dont tell us clearly:
"At full throttle can’t get over 3200 x 3800 rpm" - which engines? Port 3200 Stbd 3800?
"Psi’s are 3.4 then the port is 10" try to be consist Port then Starboard - so Port 10 psi, Starboard 3.4 psi
"There is a slight pull on the starboard engine at full throttle as well" the BOAT (not engine) wants to turn to starboard?

Now re-read the above and see why it is confusing?
Which is weak?, the Starboard engine seems to be the weak engine, low psi, the boat is pulling to Stbd, but Stbd has higher RPM?

Please clarify...
 
hughespat57 said:
As @Espos4 pointed out your asking what seems like simple question, "why" but you need to provide specific details about performance issues.

What are the exact models (get the model and serial numbers off the engines) so we can look up the detailed parts lists and manuals for you.
As asked before:
Did you have a survey and sea trial performed before purchase? When?
Has it ever been able to reach WOT?
WOT on both engines?
Currently there are NO alarms, or warning codes?
How old is the fuel in the tanks?
When was the fuel filters last changed? Primary and secondary filters?

If NEITHER engine can reach close to WOT the chances of both engines having different problems at the same time is nil.
If one engine is having problems the other is doing all the work so it wont reach WOT but should be considerably high then the "weak" engine.

Be very specific with any response, we dont know what you mean if you dont tell us clearly:
"At full throttle can’t get over 3200 x 3800 rpm" - which engines? Port 3200 Stbd 3800?
"Psi’s are 3.4 then the port is 10" try to be consist Port then Starboard - so Port 10 psi, Starboard 3.4 psi
"There is a slight pull on the starboard engine at full throttle as well" the BOAT (not engine) wants to turn to starboard?

Now re-read the above and see why it is confusing?
Which is weak?, the Starboard engine seems to be the weak engine, low psi, the boat is pulling to Stbd, but Stbd has higher RPM?

Please clarify...
Click to expand...

Very sorry for the confusion, it’s has been very frustrating trying to solve this problem. The boat is a 2007 sea ray 5.7 350 with vdrives. Serial #0W693395. When the starboard engine gets up to 2900 rpm’s the rpm’s shoot up to 6500 to 4500 to 3500 to 2900. Basically all over the place. We have checked anti siphon valve, plugged fuel tank vent, no water in fuel, replaced fuel filters, replaced spark plugs and wires, replaced distributor cap, replaced ignition coil, no play in distributor shaft. The only thing we have not done is a compression test but the mechanic tells me the engine would be running rough at low rpms and doesn’t believe that is the problem. He seems to think it’s electrical and wants to replace the main electrical harness? I did not have a survey done on the boat because of the price I thought there was enough room to fix the issues. Hopefully this gives you clarity on what I am trying to fix.
 
When the rpm “shoots to 6500” can you actually hear the engine screaming? Because that’s way beyond the rev range for that motor.

Even a jump to4500 rpm the 350 will have a noticeable noise difference.

This could be simply the tachometer acting erratic (engine noise doesn’t change at the indicated 6500 rpm) or your transmission is slipping (engine speed actually increases as you pass 2900 rpm).
 
Well that description is more to the point I guess..
Please correct anything that is wrong here.

The engine is an MPI 350 MAG MPI MIE
https://www.perfprotech.com/mercury...serial?#/serial/0W693395/Model:24554328195604
Is it a Digital Throttle Shift? (DTS)

The issue is only the starboard engine, no over heating now, no codes now, but still indicates low water pressure
RPM is erratic, under load, idles ok.

Over revs to 6500 some times? In gear?
If this is true the engine is loosing the "load" there is no way it will really rev that high in gear if the drive train was good (unless cavitation the prop some how)
Have you check the transmission? Be sure its fully engaged and its not slipping?
Check the shaft coupling have you sheared the key?
Same at propeller sheared the key?
 
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