Overheat due to weeds - need advice

[Redtruck12]

So due to Covid19 and a new job yesterday was the first day on the water for my Restored 1974 Duo Vagabond (140 hp Mercruiser 3.0 litre.
rented a cottage on Pigeon Lake in the Halliburton Highlands (Ontario). Shallow and weedy lake.
first run I noticed a bit of what I assume was prop shake from weeds which cleared after bringing the engine up to speed.
engine running fine but after about 10 minutes engine temperature climbed to 200f on the gauge.
I stopped and shut the engine off. Lifted the engine cowl and smoke was evident. Evaluated the source and pinpointed as VERY hot manifold.
checked for weed clogging the water intake on the drive - there were weeds.
limped back to the dock at not much more than idle.

question is now what?? What should I check? Should I replace the water pickup pump before running it?
I’m fairly confident I have not damaged the engine and would prefer to keep it that way.

next question is advice on how to avoid it happening again

 

[Bondo]

next question is advice on how to avoid it happening again

Ayuh,..... The impeller might be Ok,..... Time will tell,.....

Always idle through weeds,..... once beyond, a short quick blast in reverse will clear the weeds away from the drive,....

 

[Rick Stephens]

With impellers, if in doubt, pull the hose off the thermostat coming from the transom up the port side of the motor. Hook up your muffs and give it full water. Fire up the motor and point that hose at a bucket. Should fill a 5 gallon bucket in under 20 seconds.

 

[Redtruck12]

Thanks Bondo
the reverse trick is what the locals have recommended.
I am hoping that my temperature gauge is accurate and it was only the 200f that it read.
what would be the telltale signs of a bad impeller othe than hi temperatures?

 

[Redtruck12]

Thanks Steve Any way of checking the impeller with the boat in the water? Same as on muffs?

 

[Redtruck12]

Okay
so I disconnected the hose at the base of the housing (boat still in the water) ensured no weeds built up on the drive,
started and ran at idle and slightly above, steady flow of water from the hose (not blasting out but a steady flow.
reconnected and ran engine while Still tied up, approx 1000 rpm for about 15 minutes temperature up to about 180.... too hot?
was thinking about letting it cool down and then a short trip to check.
sound reasonable????
any opinions appreciated, kids are bugging for a boat ride

 

[Bondo]

Ayuh,..... I'd plan on doin' the impeller as soon as the boat is on the wagon,.......

 

[Redtruck12]

Okay so update
had it out for a wee ride
gauge reading between 180 &200 but consistent. No smoke or crackling sounds like yesterday’s adventure.
still seems a little bit hot to me but not sure if I’m just being paranoid.
any thoughts????

 

[Redtruck12]

Sorry you posted asI was writing.
so too hot??

 

[Bondo]

so too hot??

Ayuh,..... Considerin' it's probably got a 160* t-stat,..... Yes, that's waayyy to hot,.....

 

[Redtruck12]

Gotcha
that’s what I thought.
out she comes

 

[Redtruck12]

Update
on the trailer, garden hose and muffs still just a trickle of water.
removed the lower unit and replaced the melted pump and housing.
thankfully Buckeye Marine in Bobcaygeon had one in stock.
parking lot repairs done and checked again on hose and muffs.
all good.
back in the water this morning and running at 150-160 at speed.
thanks again for advice Iboats community

 

[Rick Stephens]

Update
on the trailer, garden hose and muffs still just a trickle of water.
removed the lower unit and replaced the melted pump and housing.
thankfully Buckeye Marine in Bobcaygeon had one in stock.
parking lot repairs done and checked again on hose and muffs.
all good.
back in the water this morning and running at 150-160 at speed.
thanks again for advice Iboats community

Love a happy ending!

You are one smart dude just knowing you needed to question it! Awesome.

 

[Redtruck12]

Correction 140deg