Unusual, throwing hot alarm

[speterson1011]

I will start with some history of the engine. 2000 Johnson 2 stroke 4 cyl 90HP. Recently rebuilt powerhead have had no problems. I'm at 60 hours on the new rebuilt one and it was broken in properly. I hardly ever run it wide open. When I do it will run wide open for about 2 minutes then start to shudder like it has an insane misfire and throw a hot alarm. I disconnected the oil reservoir and mix it by hand since the rebuild. I am 100% it has the right amount of oil. The disconnect was definitely done properly as well. Has an impeller that has maybe 10 hours on it along with the whole housing and water pump assembly. It is peeing perfect out the back. Spark plugs looked clean not burnt, or gummed up. The thermostats are newer along with the springs and I boiled them in a pot of water and they opened up. I know. I should check compression right. I think I am just scared to since its such a newer rebuild but it has been over a year and is no longer warranted. Is there anything else I am missing? When it does start to shudder and throw the hot alarm I can bring it from 4xxx rpms down to 25xx rpms and it will stop it within seconds and then I can get back up to 28xx rpms but any higher it will throw the hot alarm and shudder. Any other ideas? Thanks everyone

 

[TD_Maker]

Re: Unusual, throwing hot alarm

I am curious if the motor lower unit intake could be coming out of the water at high speeds? If it quits sucking water then it will overheat.

 

[speterson1011]

Re: Unusual, throwing hot alarm

Yes I do see what you are saying but I am 100% sure that is not the case. My boat has a low transom and it is way under even on a plane it is a good amount under water. I mean, it has never done this before. I have had the boat for 4 years now. Was rebuilt about 1.5 years ago. I probably put close to 150 hours on the motor in those years before it was rebuilt without this problem. As of 40 hours on the new power head it didn't do this. So somewhere around 45 hours-50 hours it started doing this. If I just run no more then 3000 rpms it never does the shudder and hot alarm, even if I run all day non stop. When I hit the motor with the laser temperature on each cylinder and test the pee water temperature everything checks out perfectly with the owners manual correct temperature specifications.

 

[clanton]

Re: Unusual, throwing hot alarm

Boiling water is 212 degrees, thermostat should start to open at about 140 degrees.

 

[speterson1011]

Re: Unusual, throwing hot alarm

Yes they did open before the water started boiling. I just wanted to make sure they opened but I could not guess to what temp is was opening around since I did not have a thermometer. I am going to get one and try and see what temp they open at again. Although, it idles forever and runs smooth for 25-30 minutes I have tested so I don't know if it would be thermostat related.

 

[hogan12009]

Re: Unusual, throwing hot alarm

test run it with no t-stats and see if it does it.

 

[speterson1011]

Re: Unusual, throwing hot alarm

I will be sorting it out this week. I finally have some time off. I will try running it without thermostats and see if that gets rid of the problem. thanks again everyone. I will keep you guys posted.

 

[speterson1011]

Re: Unusual, throwing hot alarm

Just wanted to let everyone know I have resolved the issue I do believe. I took the thermostats out hoping maybe a little more circulation flow would blow whatever is out of there (well what I thought). Anywho, ran it like that a couple of trips. Probably 10 engine hours. Never ran it hard, just cruising speeds. Just this week I ran it hard for about 20 minutes straight a few times nothing, no sounds anything of the not normal. Great water flow out of the pee hole and great cylinder head temperature. So, all in all. I do believe it is fixed. I at least hope. I was ran hard over a few days. towing tubes, and lots of long WOT.