Do my findings match my symptons

[TBarCYa]

Last week I took the boat out for the first time before which I started the engine on the muffs at home. I watched the temp for 15 minutes at home and it stayed around 150-180 the whole time at differing rpms. When I got it in the water I again let it run for about 10 minutes and watched the temp with the same results. Once I got underway tho I noticed that the temp got pretty high but stayed steady. There was no change in engine performance however.

Today I changed the water pump and found that the lower water pump housing showed signs of melting and the vanes on the impeller looked like they had melted as if run without water. I also had to fight with the driveshaft o-ring which was stuck in the housing and had to be pryed out with a pick.

I'm thinking that replacing the water pump has fixed the problem since the temp stayed around 150 today however when I checked with the IR temp gun, I got max readings of 127 on the exhaust, heads, intake manifold and anywhere else I pointed the gun. I believe the temp sender is at the front of the intake manifold and if so, the manifold read 127 at the sender while the dash said 150. If this is the right place to take the reading, then the gage on the dash reads high which makes me feel much better about how it ran last week.

Any suggestions on whether my findings match what I experienced last week and if I took that 127 reading at the right place would be greatly appreciated.

 

[Don S]

Re: Do my findings match my symptons

Temps will vary all over the engine, but the temp gauge on the dash only measures from one place. Check the temp with your IR gun right at the sending unit for a check of your gauge.
180? out of the water without a load is a sure sign of overheating and should have been a dead giveaway that a problem was developing.
When you have a lack of water flow, all those plastic parts in the drive are hit with uncooled exhaust gasses, thus the melted parts.
Even with a new pump, if the exhaust cooling passages are plugged up from rust and corrosion, it can also block off the water needed to cool the plastic parts in the drive.

 

[TBarCYa]

Re: Do my findings match my symptons

I believe that the 127 reading was taken at the sending unit in the intake manifold because it's the only sending unit I can find other than oil pressure. I was getting much better flow of water thru the prop after replacing the pump than before going out for the test last week I also noticed lots of water coming from the weep hole in the lower unit and from the two holes in the lower portion of the gimbal housing. I didn't take notice to the flow from these other ports prior to changing to the pump but they definitely caught my attention today.