Can lack of waterflow cause a false reading from the temp sending unit?

[nextboat1]

I recently had some idle issues on my mercruiser 5.7. Thanks to the iboats community that issue has been resolved, but has lead me to my next problem. After fixing the idle issue (rebuilt Carb), I ran the boat on muffs. I checked the temp gauge after running for just a couple minutes and it read right around 100. I then went back to the engine to check for any leaks ect. since this was my first true startup of the year. After about five minutes when it had came down from high idle I went and checked the temp again only to see it was pegged at 240. I quickly shut it down and then went back to check the engine. I felt the risers and all of the hoses and nothing felt hot. I even went as far as putting my hand against the side of the block and still felt no excessive heat. I found that the intake hose from the bellhousing to the transom plate is kinked and in need of replacement. I had water flow just very minimal. My question is, is it possibly that my temp. sending unit had a false reading due to air in the system? I can't believe that I would be able to keep my hand on the risers/block with a temp like that. Any help would be greatly appreciated. Thanks.
I forgot to mention.that the boat is raw water cooled.

 

[Bondo]

Re: Can lack of waterflow cause a false reading from the temp sending unit?

Ayuh,.... Donno what happened, but a lack of water usually leads the temp sender to read too low, or not at all...

Fix yer hose, 'n throw a new impeller in it, 'n give it another try....

 

[nextboat1]

Re: Can lack of waterflow cause a false reading from the temp sending unit?

Thanks bond-o. I had the impeller changed a couple weeks ago and plan on changing the hose (along with bellows since ill be right there) this weekend.

 

[nextboat1]

Re: Can lack of waterflow cause a false reading from the temp sending unit?

Good news and bad:
I spent yesterday replacing the lower water hose, as well as the shift, u joint and exhaust bellows since I was in there anyway. I got it all back together only to find out my hose was kinked just as bad as the original. Is there any POSSIBLE way to fix this without out taking everything back apart? Thanks

 

[dubs283]

Re: Can lack of waterflow cause a false reading from the temp sending unit?

I got it all back together only to find out my hose was kinked just as bad as the original. Is there any POSSIBLE way to fix this without out taking everything back apart?

no

you must disassemble and remove the hose - your best bet is to replace the hose altogether, once it kinks it will continue to kink in the same spot

when you get the new hose, trim about 5/8" off the end, they always come too long and that is why they kink when installed - also a little heat on the hose end and power tune on the transom barb fitting aid in installation