270 crusader overheating when trolling

[joe g]

the starboard engine has always run a few degrees warmer than port but never too hi.  first few trips this year have proven otherwise.  the starboard engine temp is fine at cruising rpm.  sat we ran out and started troll on starboard engine. after 20-30 minutes the temp creeped up so i switched over to troll on port... the temp was fine on the starboard side on ride back to dock.    got in and removed cover to find impeller in pretty bad shape.  ran down the road and had a new one put in thinking that was the simple and obvious fix...    next day tried the same thing except at trolling rpm the starboard engine got hot in 5 minutes...    again the temp was fine on the cruise back to dock.

 

any thoughts? is it possible the impeller was put in backwards or doesnt it matter with them as far as the spin goes?

[bailey]

check thermostat to see if any debris from impeller is clogging it up and chances are you have a water pump on the block that could be bad also

[lily]

Pull 're thermostat see if it opens in hot water on the stove. Also if you changed the impeller on the pump but did not change the whole pump housing your problem could be there. Did that last year my self. Only changed the impeller and the old housing ate the new impeller . when you have it apart for what it is worth I always change both. Also make sure your intake hose is hooked up inside the motor shrowed. Hope this helps. All things I've learned the hard way

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[lakebound88]

Raw water cooled or fresh water cooled?

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[joe g]

Raw water cooled or fresh water cooled?

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from the lake

[lakebound88]

So raw water, was there pieces of impeller missing? If so these can get stuck at the thermostat and cause a malfunction, also can plug your risers on your manifolds. If there were pieces missing I would try to back flush the motor.

I'm not ruling out a defective thermostat either, especially if you've had previous temp issues

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[joe g]

thanks for the replies guys.  i'll check into all of these

[dvdegeorge]

Just had this exact problem with my 270 crusader.... Almost a certainty it's the impeller in the water pump

My bearing in the pump were on the way out also so had whole pump rebuilt. Broken piece of impeller need to be remover from engine or it will restrict water flow and still run hot.

Ran like a champ Sunday temp stayed right at 140 like it should

Good luck

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Edited April 28, 2015 by dvdegeorge

[joe g]

just left the boat.. opened the housing back up and the impeller looked to be in backwards. replaced it with a new one in the opposite direction. ran it at idle for 30 mins and never got over 160.  hopefully that was it!!   i am gonna go thru all the other things listed here tho too.  thanks!

[dvdegeorge]

Good deal glad you got it sorted out

[lakebound88]

Way to go!

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[joe g]

UPDATE.. apparently the dock idle didnt mean much as it again got hot on troll.....  when got back in blew air into the thru hull intake hose and git bubbles under the boat so that is clear...

[lakebound88]

Your risers may be plugged with rust...

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[joe g]

Your risers may be plugged with rust...

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thanks.. will add this to our list of things to check... along with heat exchanger and new pump assembly.

[lily]

I still believe the problem is in your pump housing. If you pull that pump again and your impeller is all chewed up you have a bad spot in the housing. I did the same thing 3 times last year before I replaced the housing and that finally fixed the problem.

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[lily]

You need to replace the whole pump not just the impeller.

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[Xxx]

If there ever was a person that had more over heating problems than me god bless ya, I'd be leaning towards Lakebound88 suggestion I'd check the risers, mine were rusted up bad, I was told to pull them, use a coat hanger and run the coat hanger down the holes there should be 4 oval shaped holes in the riser and one in the back its down inside just before the bend in the riser its a slit and that has to be cleaned out also, the mechanic that I deal with told be to mix up muratic acid 60% water and 40% acid and let it set for an hour than rinse it out and blow it out real good with air, if you have a infer red heat gun shoot your exhaust manifold should be around 150* your risers should be 130-120* and the rubber boot between riser and exhaust pipe should be 115-95* both sides should be within 10* from each other if one side is higher than the other then it's not the thermostat it's in the risers or the exhaust manifold (heat exchangers) one of those could be cracked internally, mine took new manifolds and risers and new thermostat housing, and the list goes on but for your sake I would invest in a heat gun, like $25-30 you will use it a lot. I shoot mine all the time, I'm just paranoid from all my troubles, my rubber boots got so hot they started to smoke, Yikes, that was running off the muffs in the driveway. Hope this helps and good luck!! Oh ya change the whole water pump housing in the lower unit if they get hot the metal sleeve that the impeller spins in melts the plastic housing and it won't pump like it should, Henry the mechanic doesn't recommend just replacing the impeller for a few bucks more you get the entire housing.

[lily]

I agree with you on the risers being plugged. But I keep saying the pump housing for 2 reasons. 1 it's the cheapest place to start and should have been done when they changed the first impeller. And 2nd he is getting water to the motor at cruising speeds wich indicates that when under motion the pump is working to get water to the engine by using speed threw the water to help push the water threw out the system but at slower speeds it will not. I don't know if I explained this right. But my out board did the same thing last year. The muffs can presherize the system enough to actually by pass a bad water pump.

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[joe g]

thanks alot guys.  sounds like a great place to begin

[lily]

How did you make out Joe G. Just curious if you got problem solved

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[joe g]

Still was hot after new impeller. Took hose off between thry hull screen and pump and blew it out. Has been running great since. Thanks for all the help!