engine wouldn't start ...now overheating

B

ballinsncbirth

New Member
May 11, 2014
43
clear lake tx
Boat Info
2006 320 sundancer
Engines
350 mag
Hello all
I have 320 sundancer 06 with 350 mag mpi engines ...I started the port engine and it cranked and started for a couple seconds but then cut out ...
After 15 minutes tryng to get her to start I gave up

The next week she started fine.. However began to overheat .. Even sitting at idle the engine will slowly and gradually heat up until it alarms .. Faster if I increase the throttle

Water seems to be coming out equally from both exhausts equally .. And I don't believe its a faulty sensor

Before I start pulling impellers ,tstats , risers etc.. Any clue what could be going on ?
Thanks
 
Check for water in the oil.
 
your oil will look milky if you have water in oil.. pull dipstick and check
 
checked the oil and it wasn't milky... oil was slightly overfilled,...... will change the oil anyway ,,, any other causes? trying to connect the engine not starting ... and then starting a week later but overheating...doesn't seem like it would be a cooling issue..
 
Since there is no water in oil, separate the starting issue from overheating. More than likely it's not connected. When were the plugs, wires, cap changed? Same question on overheating. When were the manifolds and risers changed? If they are original, you are on borrowed time. If a water jacket goes, your in real trouble as you will have sea water seep into your cylinders and hydro-lock your motor (i.e., water in oil)

The overheating can be a number of different issues, but if you have original riser/manifolds, you should change plugs while they are out- it is ALOT easier to change plugs and wires with no manifolds in your way. If you get everything to where it's starting okay and just over heating; then start at sea water pump (impeller) and work your way upstream. Could be a simple stuck stat on closed cooling side, or maybe a clogged cooler and/or heat exchanger on the raw water side. Good luck
 
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sdleo26 said:
Since there is no water in oil, separate the starting issue from overheating. More than likely it's not connected. When were the plugs, wires, cap changed? Same question on overheating. When were the manifolds and risers changed? If they are original, you are on borrowed time. If a water jacket goes, your in real trouble as you will have sea water seep into your cylinders and hydro-lock your motor (i.e., water in oil)

The overheating can be a number of different issues, but if you have original riser/manifolds, you should change plugs while they are out- it is ALOT easier to change plugs and wires with no manifolds in your way. If you get everything to where it's starting okay and just over heating; then start at sea water pump (impeller) and work your way upstream. Could be a simple stuck stat on closed cooling side, or maybe a clogged cooler and/or heat exchanger on the raw water side. Good luck
Click to expand...

so the starting problem is seemingly gone and only happened once, after that the overheating issues started I figured the problems were connected,.. but your right may be a red hearing the Engine was rebuilt 1 year ago during the buying process.. but not sure if they replaced the manifold and risers... they problem need a change either way , is it possible there could be water in the oil, yet not show up on the dipstick ?(ie water and oil has separated into 2 different layers secondary to the boat sitting for a couple days)
 
Your overheating maybe related to it not starting, if you hadn't started it for awhile turning the engine over for a long period of time will mean no water flowing thru the sea water pump that could have resulted in a dry impeller possibly tearing the veins or galling and weakening them. When it did start you may have ripped a vein or 2 off the impeller, it could look like your pumping enough water but not enough to cool the engine.

I would first pull the plugs to see if you have any water in the cylinders, if not pull the sea water pump.

No oil & water will not separate once it's milky looking it stays milky.

Just my opinion someone else may have some other tips.

Good Luck
 
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Ok will pull the impeller this weekend .. I am salt water cooled by the way


if there are veins missing where do they usually get stuck at ? (Ie what's the smallest diameter tubing or inlet area ) what parts are particular vulnerable to get clogged ?


I heard you can back flush the parts out ... How is that done ?

Also if the impeller is vulnerable to having no water in the housing after I drain the engine and pump and put everything back together do I need to add water back in somewhere before I start the engine ?

Do I put a hose and just add water like flushing the engine ?

Thanks so much for the responses
 
Your salt water cooled on the raw side, but you have closed cooling (anti freeze coolant) as well. The sea water cools the heat exchanger where the coolant dissipates the heat it picks up from the block. If your impeller came apart, the pieces would be at the entry of you tranny cooler. Follow the house up from raw water pump. The holes in the cooler are ~ 1/4" so the veins of impeller usually are there and too big to pass; if small pieces come off, then it's back flush time.
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I don't have a heat exchanger /antifreeze/closed system ... both from the engine manual ...and tracing the water flow in the engine.... no heat exchanger.. unless i am completely missing something
 
ballinsncbirth said:
so the starting problem is seemingly gone and only happened once, after that the overheating issues started I figured the problems were connected,.. but your right may be a red hearing the Engine was rebuilt 1 year ago during the buying process.. but not sure if they replaced the manifold and risers... they problem need a change either way , is it possible there could be water in the oil, yet not show up on the dipstick ?(ie water and oil has separated into 2 different layers secondary to the boat sitting for a couple days)
Click to expand...

How long did the engine run before you shut down? Easiest way to see water in the oil is after it has been mixed together and turns into a frothy coffee with cream color. I've seen some engines where you could see some milkiness under the oil fill cap.
 
ballinsncbirth said:
I don't have a heat exchanger /antifreeze/closed system ... both from the engine manual ...and tracing the water flow in the engine.... no heat exchanger.. unless i am completely missing something
Click to expand...

If your signature is accurate, I would of thought you do .....2006 Mag MPI ??

Edit : You are correct, they made versions with no closed cooling ; I guess I didn't think that was even a possibility on that model/year boat.
 
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wish2fish said:
How long did the engine run before you shut down? Easiest way to see water in the oil is after it has been mixed together and turns into a frothy coffee with cream color. I've seen some engines where you could see some milkiness under the oil fill cap.
Click to expand...

The first time happened on plane .. Shut the engine down pretty quick and returned to the dock on the starboard... Started again during docking and by that time it cooled....

Ran it again on idle just to check to see if it was a thermometer issue and it gradually overheated after around 10-15 minutes up to 190 (turned it off before alarming )

just checked the the oil again today and no water

what's the best place to out the laser thermometer to get a good reading of the temp? Risers ? Thermostat ? Manifolds ?

Also so after reinstalling the impeller do I have to add water back in the engine before I start her up ?
 
Bob & Sue said:
Your overheating maybe related to it not starting, if you hadn't started it for awhile turning the engine over for a long period of time will mean no water flowing thru the sea water pump that could have resulted in a dry impeller possibly tearing the veins or galling and weakening them. When it did start you may have ripped a vein or 2 off the impeller, it could look like your pumping enough water but not enough to cool the engine.

I would first pull the plugs to see if you have any water in the cylinders, if not pull the sea water pump.

No oil & water will not separate once it's milky looking it stays milky.

Just my opinion someone else may have some other tips.



Good Luck
Click to expand...


ok so I finally got around to checking the impeller.. It was in good condition .... Then I changed out the thermometer and cleaned the t stat housing .. Had a little gunk but not to bad ....
still having the same issue .. Slow and steady overheat... The engine continues to start fine ...
any other ideas ?
 
I'm gonna throw this at the wall and see if it sticks.

Has the raw water pump failed or gotten weak? Have you checked the strainer? Were you hauled out for painting and they painted the scoop?
 
dwna1a said:
I'm gonna throw this at the wall and see if it sticks.

Has the raw water pump failed or gotten weak? Have you checked the strainer? Were you hauled out for painting and they painted the scoop?
Click to expand...

Water seams to be coming out of the exhaust equally... I'm guessing if the raw water pump was weak I would see less water out the exhaust ? ..strainers clean..boat hasn't been to the water in a year...
 
And you put in a new thermostat? With the correct temp?
Do you have heat exchanges and have you pulled the two ends and flushed it out?
when you did the impeller did you notice any issues with the hoses? Has the hose gotten soft and collapsed?
One last thing, is the seacock all the way open?
If you feel the pump is doing it's job and pumping the correct amount of water then it's time to call in the pros
 
This may be of little/no help, but I did have a hard wall hose that would collapse internally - between the strainer and raw water pump. Hose looked fine from the outside. The water flow was even (ish) at idle, but around 1500 rpm, it would collapse and the engine would start to get warm. Still had water flow, just not enough. It took a lot of troubleshooting to resolve it. I used swimming pool suction hose on the suction side and clear hose on the cooling side to finally diagnose it.

Someone will probably tell you to get one of those laser thermometers and start taking readings from various parts of the cooling system and engine block, risers, etc. (while the engine is running) before you do much else. This might help you narrow the issue.

Good luck.
 
I had a colapsing hose from my RW Sea valve to the strainer. I would colapse when under strain (when I went on plain). Also I had bad gasket on my strainer causing air to be sucked in with the water. Oh... You can't tell visually if you are getting enough flow...
 
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