closed cooling surprise

212rowboat

i made a run to a distant inlet this weekend... it was an hour and a half one way.  it allowed me to stretch that new engine out and see what it is all about- fuel consumption, temperature, charging, ect... and, it allowed me to check out a new prop too... 

less than a mile from arriving back at the launch i hear a belt squeal... ruhroh... i go to investigate- i notice the alternator bouncing a little and a fine mist of water.... not coolant but raw water... huh... i decide to chance it and continue the run to the dock.. 

i get the boat home on the hard and put some muffs on it and give her a start... squeal is there at idle but not above 900RPM... again i witness the alternator bouncing slightly, and decide it's either loose or the bearing has failed.... already... at around 10 hours run time on the turn key engine... grrrrrrrr.....

so today i finally get at it.. pulled the access panel behind the rear seat and can access the front of the engine below the heat exchange (accessory belt; WP; ect) ... and the below picture greets me:



so over a wake or wave from the inlet, i suppose, a hose shifts ever so slightly and touches the belt.. a fuse was lit. 

here is the curiosity- pumping 20gallons per minute into the boat isn't a good plan... but it wasn't... the freakin' belt served as a plug!!! it was just a fine spray that i thought was a loose clamp... 

it took literally 10 minutes to fix, and that was five minutes looking for my hose cutters (to make sure it was evenly cut).  I simply cut the cut part out and slipped in replacement hose of same length, with a nipple on either side- which is now pulling double duty as anchor point for zipties that will hold it firmly out of the way from here on. 

here is the reason i share this here:  when that system opened up, it didn't get hotter it got cooler.... like, a LOT cooler... it dropped from 170ish to 130ish... that doesn't make any sense to me UNLESS it's because water under pressure is moving through the exchange too fast to remove heat- and slowing the velocity of the flow allows more heat exchange? 

thoughts? 

and by the way.... look at that belt... it is brand new... that is what salt water and a bit of friction can do to a belt in a short period of time....  

212rowboat

and forgot to mention... the alternator is fine bearing and all... the hose obstructing took the belt ever so slightly out of alignment where the power above 900rpm re-aligned it... 

YYZRC

That’s wild. Lucky timing!!

My old boat ran cool any time it was above 1000rpm - similar 120ish temp. Never did figure it out. 

212rowboat

it HAD to be slowing the velocity/pressure of the water through the system because the risers were hot to the touch, which is not the case usually... they are usually cool to the touch as the raw water goes through the exchange and directly to them, spitting into the exhaust. 

i guess the lesson is "i have good flow"? which is better than the opposite.. this closed system was purchased from a now defunct company out of florida, supposedly engineered specifically for a alpha gen 2 drive... i would have guessed (and i DID guess before, almost going with a through hull and crank mounted sea pump) it would struggle... it apparently doesn't... but... the routing of hoses could obviously be better. 

rasbury

I would guess the temp sensor was not getting the flow on it and was a false reading...

212rowboat

rasbury said:

I would guess the temp sensor was not getting the flow on it and was a false reading...

one sensor is in the intake manifold and the other in the thermostat neck, and both on the coolant side of the flow... there is no monitoring the raw water for either flow or temperature...