running hot

[workingonadream]

i have a detroit 8v71 that is getting hit and running approx 190-195 versus 180 on the other engine. i have cleaned the exchanger, cleaned the intercooler and fuel cooler. also changed the impellerandcleaned my stainless elbows. ican see the flow out of the exhaust at idle is less than the other.has anyone ever seen a jabsco raw water pump go bad. there is no water leaking from the pump. i heard there are ceramic seals in the pump on the shaft. i am wondering if it can be sucking air, but not leaking water. any help will be greatly appreciated.

 

[SeaEric]

Does the 871 have shower heads in the exhaust that could be clogged?

 

[workingonadream]

thanks for replying. i cleaned the shower heads changed the ball valve and thru hull for other reasons ,but i cant get it to run cooler. i am wondering if the pump housing and or the cam or anything else in the raw water pump could be causing this problem. everything from the thru hull to the shower heads have been taken apart cleaned and inspected. even the pump has a new impeller. thanks again

 

[captddis]

Not sure where you are, but here in FL I have had a bunch of plugged thru hulls lately.

 

[workingonadream]

im in rhode island. thru hull is fine. thanks.

 

[Boatsb]

Cams and housings wear but usually slowly over time. If it was sudden it is probably something else. Check to see if the intake hose is soft and may be partially collapsed.

 

[yachtsmanbill]

Check the pumps' back end and cover plate for scoring...the bore also for that matter... may be a goner... Cover on the strainer or hoses sucking air? Washer in place under the covers' T handle? Is this an N or a T model? ws

 

[workingonadream]

the hose is new. this problem started last year. i thought i found it at the end of the season when i pulled the shower heads and saw debris in them. i put them back on this springand the problem continues. the boa is a 1979. the engines were majored in 06, but the pumpswere probably not. the temp doesnt shoot up, but it creeps up while on the throttles and decrease when i back off. if i stay around 1700-1750 rpms, i can run the boat without it overheating, buy if i run it at 1850-1900rpms it will climb. ive done eveything but change out the pump. thanks

 

[MikeP]

How did you clean the heat exchanger - what acid solution? Did you clean it in place or remove/dip it?

 

[captddis]

The seal can suck air as can the strainer and hose. There is only a small section on the pump inlet that can be clamped to or that will suck air.
Did you remove the exchanger and have it ultrasonically cleaned?

 

[Boatnut]

Could it be possible, the thermostat is bad, or the raw water circulation pump etc. be bad. I am asking to learn, no trying to advise.

 

[workingonadream]

i cleaned it with muriatc and oxillac acid. also their are new seals on my strainer. the access seal on the stainer cover is heavy rubber and is tightened with a wing nut. the sight glass tube seals are tightened with 7/16 nuts. if the sight glass or cover seal were not tight i think it would leak water.

 

[captddis]

i cleaned it with muriatc and oxillac acid. also their are new seals on my strainer. the access seal on the stainer cover is heavy rubber and is tightened with a wing nut. the sight glass tube seals are tightened with 7/16 nuts. if the sight glass or cover seal were not tight i think it would leak water.

First, The strainer can suck air and not leak, Second pull the exchanger again and get it ultrasonically cleaned. The acid does not properly clean the FW side.

 

[captddis]

Make sure the seperator fins are tight against the housing.

 

[workingonadream]

howcan icheck the strainer for an air leak. i dont want to crank the nuts on the too tight and break it. i hear what you are saying and you may be on to something. thanks

 

[captddis]

howcan icheck the strainer for an air leak. i dont want to crank the nuts on the too tight and break it. i hear what you are saying and you may be on to something. thanks

Typically there will be bubbles in the strainer. If it is sucking air at the pump you won't see it. My money is on the exchanger.

 

[workingonadream]

i took off the elbow covers saturday and i was able to see thru the bundle to the otherside. it appeared to be clean. if the fresh water is not clean, how would this affect my flow

 

[Daybreak]

Im having the same problem with one of my cummins 903's. Checked through hulls, impeller, showerheads too. Temp creap at speed and low flow.

Ben

 

[SeaEric]

I have this same problem with my stbd 8v53 and my mechanic is gonna get into it in the morning. He's going to remove the HE for professional cleaning, do the impeller and T-stat. Not sure what else, but he thinks it will be OK after he's done. He has rarely seen OH problems that required a new HE tube bundle. He says that eventually the metal just doesn't carry away the heat for some reason, and new HE guts fixes it. Not cheap, but ya gotta do what ya gotta do. He had no specific explanation for why this happens.

 

[captddis]

i took off the elbow covers saturday and i was able to see thru the bundle to the otherside. it appeared to be clean. if the fresh water is not clean, how would this affect my flow

Are you sure it is low flow at speed? Does the exhaust steam more on the hot engine?