Help Please! rpms higher after new impeller

[bobo3020]

Last time on the water my water pump froze due to impeller being chewed up. I changed impeller and thermostat since housing was off while checking for impeller pieces. First time out since, I did have heavier than normal load, but noticed that rpms ran higher than usual. Also noticed that engine was running a little over 175. The thermostat is 160. Also had to remove belt to access water pump. Could belt tension effect rpms?

I'm running a 1999 Mercruiser 5.7 V8 with a Bravo 3 outdrive. It's on a 23ft Rinker Captiva Cuddy.

I want to be sure that there isn't something else that could be wrong. Any advice would be appreciated.

Thanks

 

[bobo3020]

Re: Help Please! rpms higher after new impeller

Any ideas would be appreciated!

Thanks.

 

[QC]

Re: Help Please! rpms higher after new impeller

I am confused . . . Are you saying that your WOT RPM is higher? Or is the RPM per MPH higher? Which would indicate more prop slip which would be normal for higher load . . . Temp could be higher due to impeller pieces still stuck somewhere or you could have a damaged temp sender after an overheat.

 

[ziggy]

Re: Help Please! rpms higher after new impeller

normal range of a 160* tstat would be starts to open at 160*, full open +20*. or 180*.....

 

[bobo3020]

Re: Help Please! rpms higher after new impeller

QC,

Yes, higher RPM's in both cases. The temp has remained steady right above 175, however there was one small piece of impeller that we didn't find.

Unfortuneately, I'm batting 500. 4 outings with new boat led to 2 good days and 2 bad. Mostly due to maintenance items. I've since changed all tires on trailer and impeller and thermostat. What other maintenance items on the boat/engine should I perform to avoid further problems on the water?

Thanks!

 

[bobo3020]

Re: Help Please! rpms higher after new impeller

Thanks Ziggy, makes me feel better about the temp!

 

[QC]

Re: Help Please! rpms higher after new impeller

WOT RPM higher after an overheat and then an impeller change . . . ??? Man, that's gonna cause a run on impellers . . . I have no idea why that would be so . . . Top speed go up too? Keep this one quiet until you figure it out . . . LOL

 

[bobo3020]

Re: Help Please! rpms higher after new impeller

LOL...I always seem to find the mysterious problems or maybe they find me!

Not sure if top speed went up, speedometer doesn't work, hole is clogged. It didn't seem like it lost top speed, but I did notice that I wasn't getting the normal speed to rpm ratio, it was less. However this could be due to the extra weight as well.