5.0 GXI-E Overheating

Jpistolero02

Recruit
Joined
Sep 7, 2020
Messages
2
I have learned quite a bit by reading previous posts on this forum, but I could use a hand. My dad has a 2004 FourWinns that has a Volvo Penta 5.0GXI-E. For about 3 years we have been experiencing intermittent overheating issues. He has had the local marina out several times and they pretty much swap the impeller and leave. This weekend I went ahead and swapped the whole raw water pump and impeller. The prior weekend I couldn’t drive the boat under 3K RPMs without it overheating. After swapping the pump this weekend, the boat works perfectly while operating at anything over 1K RPMs. If I drop under 1K RPMs, the heat will slowly start climbing. Any ideas on what else I can troubleshoot? It’s just really frustrating because if we get in a no wake zone, we know the temp will start to climb. The boat is solely used in freshwater.
 

Jpistolero02

Recruit
Joined
Sep 7, 2020
Messages
2
I went ahead and replaced the thermostat today, so that’s not an issue. I drove around the lake just fine today at normal operating speeds, but it can’t go below 1K RPM without overheating. I shot some temperature readings while it was hot and it seemed like the area around the circulating pump was the hottest. Is that area supposed to be hot? The impeller was right around 100 degrees as was the manifold area. The area around the thermostat was about 185. The area around the circulating pump was about 197.
 

dypcdiver

Lieutenant Junior Grade
Joined
Nov 1, 2005
Messages
1,016
I fitted 2 x clear plastic hoses from thermostat housing to manifolds, and observed that at 600 rpm I had little or no flow to the manifolds. Then at 1500 rpm I had a stuttering flow. At 3000 rpm I had a continuous flow however there was gas entrained in the flow.

This was the cause, exhaust gas had eroded the bronze tube, that is on the raw water suction side.
 

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Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
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Jul 23, 2011
Messages
47,307
look at the raw water inlet casting on the drive. if its plastic, it may be cracked. if its metal, it may be corroded.
 

QBhoy

Fleet Admiral
Joined
Mar 10, 2016
Messages
8,286
Check the power steering cooler hasn’t got an issue.
apart from that, is the alarm sounding ?
 
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