1998 130 Saltwater High temp alarm

[John9861]

Ok guys I know you've been down this road before but now it's my turn. No matter how I get there fast or slow once I reach 4000 rpm the high temp alarm goes off, engine throttles down to a high idle, runs rough for 10-20 seconds then quits & we're back in business. Took it to a yamaha certified shop where they diagnosed the following: High rpm jets in carburetors needed replacing, replaced water pump housing & impellar, replaced pop it valve( sorry I forgot the actual name). All this & it still has the same problem. So I pulled thermostat covers & found some build up so I cleaned up the area & replaced the thermostats. Still does it. In the yard with ear muffs on I can take the idle up a bit & with my temperature gun I get the following readings:
approx 120 all around the thermostat areas. 145 around the sensors. I forgot the gun today when I took the boat out for a test ride. I was planning to ride for 10 minutes or so then take it up to 4000 rpm & after the alarm goes off & idle down take some measurements. It sure seems odd though that the alarm goes off at exactly 4000 rpms. So my question is are my temps ok? Why does the high temp alarm go off at exactly 4000 rpms? This motor is on a 17.5 ft Scout Fiberglass boat & it performs extremely well. I hardly have a reason to run it at or above 4000 rpms but when I'm in a hurry I'm in a hurry...

[rodbolt17]

are you positive its overtemp and not low engine oil tank alarm?
they both use the exact same horn and tone.
only way to tell is by the tach visual indicate.

[John9861]

The temp blinker above the temp icon on the tach blinks while it is happening.

[rodbolt17]

then after carefully replacing the water pump, remove the head covers and heads.
clean all the scale and debris.
reassemble.
its a false detect.
if it were an actual loss of water or a hung T stst it takes about 15 min to cool back down and reset.
your getting a hot spot.

its rather typical for older saltwater engines.

[John9861]

Thanks Rodbolt. The waterpump & impellar were changed a couple of months ago. I'll pull the heads & clean up the water jacket. Is there anything special I should spray in the water jacket to help with this? I'm thinking the previous owner did not do much flushing after saltwater use & also did'nt use the boat much. The few times I used it after first getting it I had no reason to push the speed as it's a lot of motor for this boat. This motor is a hard start as well. I have to up the throttle in neutral, choke & after a couple of applications of the choke it smooths out. I'd like to get all this under control since it looks like I will be able to visit the water more often this year.

[99yam40]

That sounds like the normal start procedure for motors with chokes, might see if you can get you hands on an owners manual to read up on what Yamaha says and a service manual if you plan on working on this motor yourself.

seems like I have read about a flush used for heat exchangers and was also used on outboard motors to clean up deposits, but I cannot remember the name of it.

Good luck on removing all of the bolts needed on a motor that has been living in salt water.

I found that thread on cleaning product, have a read
http://www.yamahaoutboardparts.com/f...g-th19434.html

[John9861]

I found that thread on cleaning product, have a read
1989 115 ETLF Overheating

Thanks for the lead. I checked it out & my thermostat covers were no where near what was shown in those pictures. Was barely enough for me to do a little scraping. The dead end arewas were corrupted a little more similar to the pictures. This motor has less than 100 hours even though it's a 1998. The original owner became too ill to use not long after purchasing so it mostly stayed in the garage. His wife finally parted with it a couple of years after his passing. The 2nd owner didn't use it much so it may have suffered from lack of use. I hope that's all it is...

[99yam40]

Just had a thought

What are the chances that when up on plane at that high of RPM there is a problem with the water intake sucking air due to something disturbing the water or coming out of water too far.
Something to think about

[John9861]

Update tume. Pulled head covers & heads only to find a good bit of deposits needing to be removed. Manually cleaned all the scale & deposits & replaced with new head & head cover gaskets. Went to the water & now the high temp alarm does not come on. Yay for that. However, I am wondering about the engine shutting down at idle sometimes. This requires a restart with use of choke & neutral reving. I was concerned with the feel of my primer bulb so I replaced it but feels the same & engine still cuts out. I also replaced the spark plugs with Champions just in case. Could I be sucking air somewhere? Primer bulb never gets tight but moves enough fuel to start. Shouldn't this motor be able to idle in or out of gear for extended periods of time such as slow *****ing?

[99yam40]

Primer should get firm
check fuel pumps for pin hole/leak
Carbs needle and seats not closing off properly
or sucking air somewhere

It should idle properly and slow *****

Make sure you use the proper plugs as you can hurt a motor by using wrong heat range

[John9861]

I did notice a light fuel film on the water around the motor when I stopped the boat. When I changed the primer bulb I made sure to not connect the downstream side while I held my finger over the end while squeezing the bulb. Drew fuel very well with no sign of drawing air. Recoonected but not happy with the feel. Did not notice any residual fuel inside the cowling. So now I'm on to 99yam40's suggestion of pumps & carb issues. A little surprised that the mechanic who recently said the high speed jets needed replacing didn't recognize any other issues with fuel pump & carbs...