Strange situation

[km1125]

I think it's a big waste money and effort to change the gauges and senders with the data you've provided so far.

When you posted "190 going 3500 rpm. When I slow down to 2000 rpm the temp goes to 180", that means the engine temps are actually changing. The gauges aren't going to be more or less accurate at one RPM than another, so you actually have a temperature issue with the engines. Knowing that your impellers are 4 years old, as bud says, you're REALLY pushing it. They CAN last four years or even longer but they can also last as short as ONE year, or can be damaged in SECONDS if someone previously ran them dry or they ingested sand or debris. Impellers are one of the CHEAPEST things to do in maintaining a boat and you should have confidence that they're in good shape. In virtually all "unknown heating issues", the FIRST thing that should be considered is IMPELLERS.

As to location, on a Crusader big block they're usually on the starboard side of each engine and mounted low, unless a previous owner changed them to a crank-mounted pump. (post some various pics of the engines and it'd be easier to point them out). Normally you can follow the big hose from the seacock, to the strainer and the next thing that hose would likely hit is the raw water pump. It's probably easier to access the one on the port engine than the starboard engine, but they're both accessible as they are regular maintenance items.

[AlexB]

That’s what one of the marine mechanics I spoke to told me. I have two things going that makes me think it’s impellers.
One like you said they are 4 years old.
Two, I have the first spot on the dock and when the tide is low I kick up a lot stuff from the bottom when I put the engines in gear. He said knowing that I need to clean my strainers and definitely check impellers. The sand doesn’t get stopped by the strainers and over time will wear out impeller blades.
So I guess I will be changing impellers.
Any suggestions on which ones I should get? Or are all brands are the same as long as they fit.

[AlexB]

What do you think of this one
https://www.go2marine.com/18-8926-Impel ... s-Crusader

Thanks

[km1125]

Sierra ones are probably fine, so long as those are the right model to fit your engine. I personally haven't had an impeller (even a "Chinese" one) that was bad or failed prematurely but I know I've read plenty of stories from other folks who have. All the ones I've replaced (either mine or for friends) have had reasonable lives or were abused and failed from that abuse.

You should also carry at least one spare (so if you don't have one then buy an extra) and know how to change it "on the fly". There are many trips and weekends that get ruined because of a bad impeller and a replacement can't be located quickly.

[AlexB]

Thank you. Ordered 3.

[bud37]

Good stuff....show us a pic of the ones that come out if you can, they may tell a story....

[AlexB]

Will do.

[AlexB]

So changed both of the impellers today.
Port engine showed 180 idle
Starboard showed 187 idle.
I am thinking when all the panels are closed both will be at 190 again.
The impellers looked good but I still put new ones in.
Take a look.
Looks like water pump was not the reason motors run hot.
Next week mechanics will put in new temp senders. Hoping that will help.

[Viper]

Changing the impellers was a smart move because of their age but I think we already established early on here that if you were reading 165 at the engines while the gauges read much higher, that the engines were running much cooler than the gauges indicated so the likely issue was the hardware designed to report engine temps. The senders, wiring, gauges, connectors, plugs, etc. is where I'd be focusing on first.

[km1125]

Source of the post Changing the impellers was a smart move because of their age but I think we already established early on here that if you were reading 165 at the engines while the gauges read much higher, that the engines were running much cooler than the gauges indicated so the likely issue was the hardware designed to report engine temps. The senders, wiring, gauges, connectors, plugs, etc. is where I'd be focusing on first.

I don't think that was ever actually established, or at least not articulated in this thread. There were several readings (by the mechanic and by the OP) where they measured 165 or 170 on the engine, but never indicated what the gauges read at that time.

Also, lets say the gauges are off by !0 degrees or so... how would that explain the temperature rise from 180 at 2000RPM to 190 at 3500 rpm?