running hot, need help with pressure test

[vicsponjr]

224 merc, closed system. In the driveway she runs at 155. Normal running temp for her is 175-180. Merc dealer says its normal for these, says back in the day factory suggested dealers should put resistors in guage to lower reading temp. Had 8 people on a '85 19'open bow (legal capacity) and it went up to 225. I did a pressure test using a drain hole in the reservoir, plugged the overflow hose, and I hear air leaking past the cap, down past 10lbs. relatively new cap. Maybe air will get by?? Maybe I should try filling reservoir up to cap level. Any feedback WELCOME! (even a little abuse is tolerated)

 

[Dunaruna]

Re: running hot, need help with pressure test

Let see if I got this straight, the dealer is saying that your gauge has been modified to be inaccurate, on purpose?<br /><br />Specifically, what pressure did you use for the test? Could be a faulty cap (even new caps can be faulty) or the seat is rusty/warped inside the exchanger.

 

[vicsponjr]

Re: running hot, need help with pressure test

"the dealer is saying that your gauge has been modified to be inaccurate, on purpose?"<br /><br />No, he didn't say my boat was modified, he said that in th past the factory suggested modifying the guage to read cooler. <br />I believe my boat is running warn because the pressure is not building up in the cooling system, therefore not raising the boiling point and subsequently running hot. <br />The seat is not rusty but there is a crack at the very top of the neck, but well above the seat of the cap. I'm guessing this is brass? Maybe I can find someone to braise it??

 

[vicsponjr]

Re: running hot, need help with pressure test

When I bought the reservoir cap the guy at the marine shop asked which kind I wanted, said there was two different types. Is this true? If so is there a big difference, I mean could I possibly have the wrong cap on there, or is the neck of the reservoir possibly worn?

 

[paultek6]

Re: running hot, need help with pressure test

if your anti freeze mix is too strong you will show a higher reading and run hotter.