Everything is hot

[splashlog]

Got the old thing running today. Runs fine at idle load/no load, no choke, spitting out water fine 20 minutes..
Try going up on the throtle runs for a minute then shuts down. Just before the shut down it sounds like there is nothing in the exhaust, sort of an empty sound, then the shut down, then about 10 seconds later I can hear water sizzling somewhere in the system.

I read about 450F off the exaust pipe. The flywheel cover is hot to the touch. The coil is very warm, While running the thermostat cover is about 80-90F. Today was hot 30C+

Should I yank the themostat and see what happens?
If the thermostat was not doing its thing, and there was a blockage in the cooling would the engine be shutting down from overheating?

I did blow some air through the exhaust to check for flow, and that seems to be ok. Next to no back pressure

I don't have a water temp sensor hooked up, so I don't know what the water temp in the head really is, I am just using a IR temp meter.

[ndutton]

Although your post didn't specify, assuming you are raw water cooled here is a table of running temperatures taken with an IR temp gun all over a good running RWC engine with the new MMI thermostat. Offered here for comparison to what you are reading.

Your report of water flow stopping is not good. About removing the thermostat, unless you also block the bypass you risk making things worse.

[Al Schober]

First run? Cooling water is probably picking up and moving a lot of crud.
Definitely remove the thermostat until you get it running cool. T'stat will stop a lot of crud right there. Another classic spot is the output elbow from the manifold.
I got mine running cool even after installing the heat exchanger. Decided I liked it that way and left it running cool.

[splashlog]

no love

Pulled the Tstat today, still runs at idle and spews water no problem. Turn up the RPMs and she shuts down almost instantly. I can hear this weird sound coming from the exhaust just before the crib death. Ten seconds after shutdown I can hear water hitting something hot.
Going to try to hook up the temp gauge next time to get an idea about temperatre.
When I got the boat (8 years ago) it had a temp meter that allways sat at 130F, that was because as I found out later, it was not actually connected....So I may never know if there was a developing temp issue..
Anything I can look for at this point?

[roadnsky]

...then about 10 seconds later I can hear water sizzling somewhere in the system.

Can you give us an idea approx where? Might help narrow this down a bit.

I read about 450F off the exaust pipe.

Which place in the exhaust?
450-500° is just about normal.

The flywheel cover is hot to the touch.

THAT is a strange one!
Any noise coming from there?

The coil is very warm, While running the thermostat cover is about 80-90F.

Can you shoot a temp of the coil next time? When you say warm, was it too hot to touch or just warm?
That thermostat cover temp is actually pretty low. Certainly not Hot.

[edwardc]

Check and replace your water pump impeller. It might be ceasing to pump at higher RPMs

[splashlog]

RPMs

I can run the engine fine at idle (very low RPM), as soon as I move the throtle more than 1 or 2mm on the arm on the carb she speeds up just a little and then stalls right out.

I can't get anywhere near the RPM I would expect to normally have.

The sizzling I think might be water coming back down the exaust and making contact with the hot pipe, as to why it takes about 10-15 seconds after the shutdown, I have no Idea.

Water pump is fine, I opened it up, all is good.

Will try to get more temp readings tomorow

[scratchee]

Maybe you just have a problem with the main jet in your carb (separate from the idle jet, which seems to be working fine). Could it be that your engine is just normal hot but not overheating?

Check out this carb video from Moyer: https://youtu.be/kHuemGC_PHA?t=168

[splashlog]

Water ethanol and more fussing about

I pulled the carb off yesterday, (I have a spare) when I drained it the fuel that came out looked a tad bit milky....Fuel coming out of the fuel system is crystal clean. I am going to take a guess and say that water is somehow getting in carb. I have a cover that sit's over the flame arrestor as the FA sits under the stair piece and is in no way protected from rain water.
I am going to check for the presence of ethanol later today, even though I use 100% gas everytime--Or so I have been lead to believe...

[splashlog]

More to note

Today it was a bit cooler and dryer than what we have been having last few weeks.
The beast starts OK with full choke, warms up, I lose the choke, runs for a few minutes and dies.
I have put in valve after the water T inlet.
I also re installed the alternator, thinking perhaps the ignition coil was not getting enough juice.
Anyway, it seems like every time I start, it runs for for less and less time with each attempt.
It's got brand new SAE 30 oil three days ago and is right in between Full and Low.
If it is running and I try to up the RPMs she dies right away. If I let idle with or without choke she dies sooner or later (within 10 minutes)
This leads one to think it is temperature related, but changing the valve settings seems to not have any effect, and water is being shot out the transom regardless of the valve setting (full close, full open, 25/50, 50/50 etc)
The coil is cool today, both batteries are healthy.
OP reads 50PSI and allways has unless run for long times then it would dip to 40/45 PSI
And this mysterious post shut down sound is still happening
What am I missing here???
Someone set me straight here on one thought; If the oil pump were to be NFG, I would assume the oil pressure would drop to 0, yes?
Should I swap out the coil yet once again?
Should I stop spending time on this early model and focus on the rebuild?

[scratchee]

Did you confirm that you have raw water cooling, ie, no heat exchanger? Is the water coming out the back warm or cool? It should be warm.

If you have a heat exchanger, have you checked the level of coolant?

[roadnsky]

...when I drained it the fuel that came out looked a tad bit milky....Fuel coming out of the fuel system is crystal clean. I am going to take a guess and say that water is somehow getting in carb.

Did you replace the carb and find the source of the water intrusion?
How was this resolved?

[splashlog]

Follow up #1

It is raw water cooled (no heat exchanger)
I did not check the water temperature exiting, kind of tricky on my boat but I guess I can lower a bucket to catch some water.

The carb thing is strange, I did not figure out how water may be getting in, the other carb gave me trouble as I forgot that the throttle arm is broken and did not have any means of securing it, so I restored back to the original carb. I do have a 3rd carb that I will swap out today just for FUN..
I will swap out the coil as well just to see if that makes any change.
AND I will see if I can get water a temp sender to talk to the gauge.

[Don Moyer]

Fuel supply

Splashlog,

Your most consistent current symptom, which has remained throughout your thread is that the engine starts and runs fairly well at idle but shuts down at higher power settings. I'm guessing that it will start up almost immediately with the same symptom prevailing? This particular symptom is very consistent with a fuel pump failure which lets you trying to operate on gravity flow alone. Is your fuel tank level with or slightly above the engine? Don

[Sam]

Once again the often recommended 0-15psi fuel pressure gauge installed between the pump and carb would be very informative. Inexpensive and easy to install [with adapter]. If Don's suggestion is right you would see the pressure drop to near zero from 2-3psi. [Suggest Marshall liquid filled stainless steel w/glass lens]