165 Overheating

[Will Fish]

So after a long spring/summer, I finally was able to get the boat in the water after new motor, gimbal housing, transom, etc.

The good news: No water at all in the bilge
-Engine sounds fantastic and smooth as can be

The Bad: I ran for about 20-30 min at varioius speeds gradually increasing and decreasing. Everything was running nice an smooth, oil pressure at 40, temp at 125 (no thermostat intalled yet). When I pulled into the bay to pull back on the throttle for a no wake zone, my temp climbed rapidly. I had lost all water flow on my intake. I let her cool down and had to run home off my wash down pump. while running home I checked the intake and she had water flow, so I tooke off the washdown pump and came in on as normal, running 2800 at 140 deg. Once again as I pulled back on the throttle in the marina, the temp climbed.

I'm obviously not getting the proper water flow. The impeller and drive was all redone last year, and has about 15 hours on it. Although this may still be the problem, I really am baffled on this one. I have water then no water, then water and then no water. It really does not make sense. Any ideas?

 

[ziggy]

Re: 165 Overheating

I'm obviously not getting the proper water flow

no thermostat intalled yet

Any ideas?

put the t stat back where it belongs. might not be the issue, but a t stat give proper water flow throughout the engine. w/o it, water flow will not be proper.

 

[Scott Danforth]

Re: 165 Overheating

^+1

unless you have installed a restricter disc vs the thermostat, your passing fluid too fast for it to be effective, and wont flow where its supposed to.

what kind of engine/drive
are you boating in fresh water or salt?
what temp does it get to with the thermostat installed?

 

[Will Fish]

Re: 165 Overheating

the boat is a 21' Scatcraft (only made 3 years before the mold was sold to formula). Its a GM 250 inline 6 matched to an Alpha 1 Gen 1. Raw water cooled in salt water. Not really sure on temp with the thermostat, as I just got the motor in.

 

[Scott Danforth]

Re: 165 Overheating

I would check the manifold riser and manifold since your in salt water. after a few years, the passage ways get clogged with rust and do not let water out of the engine. If you just put the motor in, then hopefully you have new manifold and risers.

if you just put the motor in, and not put a thermostat in it, how do you know you have an overheat issue?

 

[Will Fish]

Re: 165 Overheating

When I was running, the temp stayed at about 125-130. once I pulled back on the throttle, the temp climbed to 200 before I shut her down. The pickup hose in the boat was hot, indicating to me there was no water flowing. When I ran home, the intake hose was cool after about 10 minutes, which makes me think water was flowing. I shut the wash down pump off and ran home slow, at a good temp, so I think the impeller is working and I must have picked up a bag or something that just blocked the water passage holes on the drive. But it happened again as I pulled back on the throttle in the marina. I did nto run the motor hot. The second she hit 190-200, shut her down and let cool before restarting. The manifold and risers are brand new.

I need to check the hose to ensure it didn't pop off, as I just completed a full overhaul. It just seems weird that the pump works then stops when I pull back on the throttle.

 

[Scott Danforth]

Re: 165 Overheating

if the temp climbed that one time, could be a hanging thermostat, or you could have sucked some debris into the system

why do you have the wash down pump running, and how does that effect the engine cooling?

 

[Will Fish]

Re: 165 Overheating

Over heated 3 times, always when I pull back on the throttle. When I wasn't getting any water flow from the outdrive intake, I connected my wash down pump to the thermostat housing. I have a hose fitting I installed on the top of my thermostat housing so I can flush the motor after each use. This allowed me to get home, should I have a problem. After I was running for a about 10 minutes I checked the intake hose from the transom and it was cold, pumping water, so I shut the pump off and ran soley on the outdrive impeller pumping water into the motor for cooling. This kept the motor cool until I pulled back on the throttle, which is when I started to overheat again, and my water flow stopped.

I'm leaning toward a kink in the intake hose, since the impeller seems to work at times. Unless this is a sign of a failing impeller?

 

[Scott Danforth]

Re: 165 Overheating

when was the last time you change the impeller? if more than a few years old, its time to change it.

 

[Will Fish]

Re: 165 Overheating

July last year. It has about 10-15 hours on it.

 

[Scott Danforth]

Re: 165 Overheating

if at any time the impeller ran without water, it will be toast. this will include a dry start, or even running into a plastic bag in the water.

did you replace the whole housing, or just the impeller?

 

[Will Fish]

Re: 165 Overheating

The entire drive was re-done. I have never ran without water, unless I sucked something up, but wouldn't the impeller just be toast, and not work on and off?

 

[Scott Danforth]

Re: 165 Overheating

your impeller should be capable of putting out something along the lines of 19gpm and just shy of 20psi

if the housing is bad, or the impeller is bad, it will still flow some water, just no where near the right amount of water.

normally if there is an overheat issue the things to look at is the raw water pump. the second thing is the raw water pump. then after that, the remaining components in the cooling system.