I need some Mechanic talk..

[iloveboatingny]

Hi,<br /><br />One of my 318 engines has been running hot if I go over 3000 rpms (temp would climb fast to 180 and if I didn't slow down, the temp would continue to rise. Since the manifolds and rises are old, I replaced all of them this morning.(900 bucks!) <br /><br />I then took the boat out for a test and although I went a longer distance, the temp still went up to 180. I then slowed down, because I didn't want it to rise any further.(if in fact it would have gone up any more. I wasn't going to find out.)<br /><br />QUESTIONS:<br />Why isn't it staying cool? Would a bad thermstat make the engine hot at higher rpms and run normal temps at low rpms?(which it does run normal temps at lower rpms)<br /><br />How would you go about finding the problem area?<br /><br />Thanks,<br />Lou

 

[JB]

Re: I need some Mechanic talk..

Hi, ILB.<br /><br />Lots of things can cause an engine to overheat.<br /><br />Thermostat sticking partly open is one. Weak water pump, partially clogged cooling passages, other things that may allow circulation enough to cool at low output but not enough for higher loads.<br /><br />I'm not real familiar with the 318s, so that it the best I can do for now. Hope it helps.<br /><br />Good luck.

 

[John Boelte]

Re: I need some Mechanic talk..

The 318 is a good engine. I'm not sure what normal operating temp is, in the automotive world, 180 degrees is not bad. My OMC 3.0 stays around 175 degrees. If you're seeing one engine run hotter than the other, you've either got (as stated above) a bad water pump, clogged passages, or maybe an outdrive water pump going bad. When's the last time the outdrives were serviced?

 

[iloveboatingny]

Re: I need some Mechanic talk..

Its not an I/O its an inboard.<br />The other engine runs around 160-170 depending on the speed i'm at.<br /><br />Here are some more "variables", when I check the gauges on the fly bridge, they read 170. When I read the gauges on the lower station, they read 180.<br /><br /> So which is right? Isn't there 1 sensor that feeds 2 gauges?<br /><br />I think I'll replace the thermostat and take it from there.

 

[elpaso]

Re: I need some Mechanic talk..

How old is the impeller in the - sea water pump -<br />if over two years, its due. The impeller may<br />look good, but with age it takes a "set" and<br />will cause the problem you are having.

 

[magster65]

Re: I need some Mechanic talk..

That's what I'd do, change the thermosthat. Did you notice if they warm up at the same rate? A sticky thermosthat will cause that engine to warm up a little slower.