am i melting things?

[artificialreef]

Hi folks, still working on my twin 470 resurrection and am real newbie to marine motors. I got 1 running and was not aware that i should change the outdrive oil before running, thought if it wasnt in gear it wasnt turning. Ok so addressed that. Changed the gear lube. Now i get it ideling and watch the temp gauge and as it gets to 150-180 degrees i smell something melting. Previosly had a problem with the stern drive going down so i tested the trim pump and nothing with 12v. So I disconnected the rams and the hyd lines and lowered the drive so i could turn this over. The burning is coming from between the transom and the 470. I did find the hyd line that i disconnected laying on the motor and melted some of the insulation but removed that and it still is burning (could just be residual fluid or rubber). I havent put in a new water impeller yet because i wanted to turn over the motor and get that runnig first. I guess my question is am i melting something because i didnt replace the water pump impeller on the sterndrive first before i ran the motor? I didnt go past 180 degrees.

 

[artificialreef]

Re: am i melting things?

Yes they were on muffs. Plenty of water running but did not see much coming out of the pinholes.

 

[Bt Doctur]

Re: am i melting things?

150-180 is fairly normal for the 470 type motors because there fresh water cooled. If the rubber exaust hoses are burning you need a new impeller in the outdrive because not enough water is passing thru the heat exchanger and out the exaust..

 

[artificialreef]

Re: am i melting things?

So are you saying i melted the rubber exhaust hoses? I saw some stories about a trap door with screws that are impossible to get out. Am i out of the woods?

 

[artificialreef]

Re: am i melting things?

Out of the woods as in not too much damage? I shut it down at 180 degrees. It may have wanted to go higher.

 

[ziggy]

Re: am i melting things?

a thermostat will start to open at it's specified value. in your case. 160*. they are full open at +20*. so 180* in your case.

i don't know a 470 version engine at all, but for any overheats, i'm under the impression that the impeller is the first place to look, specially if ya don't know it's history.

 

[Bondo]

Re: am i melting things?

I guess my question is am i melting something because i didnt replace the water pump impeller on the sterndrive first before i ran the motor?

Ayuh,... Without water flow, you're burning up the shutters,+ all the rubber in the exhaust stream...
No, you're along ways from Out of the Woods...
Just because it has closed cooling, in No way means it'll run Without Water Flow...

 

[EddiePetty]

Re: am i melting things?

....?Now i get it ideling and watch the temp gauge and as it gets to 150-180 degrees i smell something melting.?
150?-180? is quite warm to be running on muffs...especially this time of year. My 470 has a hard time reaching 140? anytime of year on muffs.
?The burning is coming from between the transom and the 470.?
Commonly, a defective impeller in the leg will disintegrate and lodge pieces of its blades on the inlet tube sheet of the heat exchanger thus restricting cooling water to the exchanger. That, in turn, will restrict the discharge water to the riser sufficiently to allow the exhaust temperature to rise to a degree where the exhaust flapper fails and lodges in the exhaust passages to the prop?s center, futher restricting exhast water flow. Most commonly the remains of the flapper can be found in the lower leg, just forward of the prop.
? I havent put in a new water impeller yet because i wanted to turn over the motor and get that runnig first.?
THIS is your first mistake. By all means, replace the impeller and while the leg is off the hull, look for those pieces of flapper.
?I guess my question is am i melting something because i didnt replace the water pump impeller....?
I would say that is a true statement !!!
Now, if it were mine:
(1)Replace the impeller (2)Conduct routine off-the-hull out drive inspections including looking for exhaust restrictions (3)Remove the FORWARD end-cap of the heat exchanger and examine for impeller pieces (4) Replace the sea water supply hose from the transom hose barb to the inlet of the water-cooled voltage regulator (if you still have it !!) with CLEAR, nylon-reinforced web tubing to allow you to monitor cooling water flow (at idle, on the muffs, the clear tubing will remain full of water: in excess of +/- 1500rpms, the restricted water flow through the muffs will cause the impeller to cavitate and you will see air bubbles in the tube).

FWIW...Ed in ?ol Virginny