runnig to hot

[keykev]

I have a 1961 23 foot Chris Craft Sea Skiff that has been flawless for 10 years with a 283 flywheel forward motor cooled by a Sherwood double impeller pump (N10360GX) driven off the back of the generator. Since the boat doesn't have thermostats, it always runs around 110-115 degrees. Upon launching this Spring, it easily reached 130 degrees at 1200 RPM. It never ran this warm, so I changed both impellers. It had no affect, and still runs warmer than ever before.
Skupper is clean and water flow is present at all hoses I have pulled off when running. Drains in block have been
pulled and checked and there isn't any sand or mud behind them. Although I have water flow at all points, I don't
believe the flow or pressure is strong enough because I can easily stop flow with my hand. Flow was checked at 1000
RPM at the dock. I thought of a major rebuild kit for the pump but the boat only has 1100 hours on it, and the pump seems relatively simple in design. Housing is smooth with no stratches, and the bushing is good, and the scraft turns
smoothly. Boat has been used in fresh water only for the 10 years I've owned it. I would really appreciate any help
I can get....I really want to go boating.
Thanks
KeyKev......

 

[Ned L]

Re: runnig to hot

It sounds like you are checking all the right things. I know the engine well, pretty simple. Running at 130? isn't a problem (esp. in fresh water), and is actually better for the engine than running at 110?. Obviously the concern is understanding what has changed. As a note, you will not get much pressure out of your waterpump. on those "Jabsco" type pumps (neoprene impeller) as soon as the pressure starts building up the veins on the impeller start deflecting and bending in, and there goes the pressure. - Just normal for them. --- Is the boat used in the same area as in the past? With no thermostat, if the lake water is any warmer than in the past (say 10?) there is a direct correlation that the engine will also run 10? warmer. Maybe just run her & keep an eye on the temp?

 

[keykev]

Re: runnig to hot

thank you for your response. I did notice the veins on the impeller are not very stiff and do not fit very tightly in the pump housing. the boat is in the same lake as always and the water temp is now about 80 degrees. I know 130 isn"t bad but your right about what has changed? I should have added that at 1500 to 1800 r.p.m. it reaches 160 but cools down slowly after thotling down. my pyrometer reads about 20 degrees cooler than the gauge reads so Iam going to change the sending unit tomorow. still though, when hot the exhaust steams more than in the past so I am still a little suspisous. I will see what a new sending unit does as it is probably the oringinal and 51 years old...again, thank you for your help...keykev..................

 

[keykev]

Re: runnig to hot

if anyone is still watching i have figured it out. yep, me, i am an idiot! i was distracted for an hour after i disasembled the pump and put the spacer behind the cover plate and not between the impellers. i realized it after finding a breakdown of the pump online. oh well, water under the bridge i guess. boat runs and cools good again. thanks.