7.4 Alpha 1 Wont stay at operating temp

[klawton55]

hi, all. i have a question about operating temp. this is my first boat its a 89 searay 23' with a 454. took it out last weekend and it would not come up to temp unless i came to a stop after a run and then it would warm up for a couple of seconds. I also found that the intake gaskets were leaking do to the bolts being loose. i installed new intake gaskets and a new thermostat, and now it gets to operating temp but doesnt stay there. it will go from 160 - nothing just like that and i can here it when it does it through the thru hull exhaust. it will continue to fluctuate like this. so my question is what would cause this? i put in a 160 degree thermostat but bought it at autozone, is there a difference from auto to marine for a thermostat?

sorry for the ramble thanks for any help!

 

[Pete104]

Re: 7.4 Alpha 1 Wont stay at operating temp

Your post is way vague! You need to read "How to post"!

 

[klawton55]

Re: 7.4 Alpha 1 Wont stay at operating temp

I apologize, let me try this again. I have a 89 Searay 23' with a 7.4 mercruiser and alpha 1. At first the engine would not reach operating temp unless hotsoaked. I then replaced the thermostat with one from Autozone it is a 160 degree. Now as I am going down the lake then engine will get to operating temp and then it will go all the way cold again. It will continue to cycle like this. Any suggestions of what could be causing this?
Thanks

 

[dubs283]

Re: 7.4 Alpha 1 Wont stay at operating temp

faulty thermostat?? sticking open??

have you tested the guage/sender wire??

verify temp with a temp gun at the sender??

 

[klawton55]

Re: 7.4 Alpha 1 Wont stay at operating temp

no i have not we just got back tonight and havent had a chance to get my infared thermometer on it yet. i thought about the sender being faulty, but i can hear it open through the exhaust when it happens, so i wasnt sure. also there are two temp sensors which one or do both work the gauge?

 

[dubs283]

Re: 7.4 Alpha 1 Wont stay at operating temp

the one with the solid tan wire is the guage sender

the one with the tan/blue wire is for the overheat alarm switch

 

[cr2k]

Re: 7.4 Alpha 1 Wont stay at operating temp

Check it with your IR gun. The only thing less accurate then a boat temp gauge is well not too much.

 

[klawton55]

Re: 7.4 Alpha 1 Wont stay at operating temp

Thanks for the information I will check it out tomorrow.

 

[Pete104]

Re: 7.4 Alpha 1 Wont stay at operating temp

If you are getting water thru "exhaust" in the beginning but loosing it later. Your hoses may be connected wrong!
Are you getting an alarm?
Have you got "Silent Choice" or something like it on this unit? That's the switch on the dash that makes it "sexy" or "not sexy"!
Gotta hand it to you for OBSERVING the intake leaks! Not everybody even checks there oil!

 

[klawton55]

Re: 7.4 Alpha 1 Wont stay at operating temp

Thanks, this is my second boat for the year so I have been causious (the first one was rotten). I am unsure of whether the water stops coming out, but i can hear when the thermostat opens the exhaust seems louder. I thought I got the hoses hooked up correctly but I can check them. Does anyone have a diagram of how they should be run? I do have the silent choice, but I have a question about that. When I switch it to go out the prop it doesnt get any quieter. I have looked and the solenoid is moving to its full length but the exhaust still comes out the thru hull. Any suggestion of why this is?