Boater_Brad wrote:
After siphoning the gas and replacing the fuel pumps and injectors, i have the boat running. Still seeing fairly high temps around the motor 150 on the risers. 143 on the thermo housing. 140 on the manifolds and the temp gauge is shot and reading 240+. Removed Risers and Manifolds as said before and cleaned and replaced gaskets with 4 hole riser gaskets. When motor heats up i lose power and cant get up over 3500 rpms. Any ideas on temps? Ill replace impellar again since it sat for a while to see if that helps. Any ideas on temp issues? Possibly blocked again?
I agree with Ray above in that both the thermostat housing and the manifold/riser water passages must be open to run normal temps. One thing though you have to do is fix the temp gauge!
The manifolds on these engines should run at about 75-100* f at idle and after coming off plane about 135 was the hottest mine ever got when everything was as it should be.
To take close to accurate temp readings take IR temp gun readings of the intake manifold right under the thermostat housing; I have found this to be the closest to the temp gauge (about 10* lower at the manifold). The top of the Thermo housing reads lower.
Have you ever done a raw water volume test with the boat in the water? This will tell you if the impeller is pumping as it should.
Google "Volvo Penta Overheat Diagnosis" this is a PDF document floating around the web that gives good tips on troubleshooting overheat problems.