1998 Horizon RXRS10 with 5.0LGi and Cobra SX Outdrive - Overheating

[ryankenn]

The numbers I got off the engine are drive are
ENGINE 5.0GI PBYCCE 4110157480 3868862
DRIVE SX Cobra 3868856 T0819692

The drive info has changed because of the story that follows. I put the boat onto a shoal and put a hole in the lower unit. Through insurance the whole unit was replaced with a reman part direct from Volvo. Since that repair the boat now overheats within minutes at speed. Its fine at low speed and during idle.

The boat never overheated before the repair, or even after hitting the shoal and limping about 20 mins to shore. The mechanic that did the repair under insurance suggested the impeller even though it only had 36 hours on it. Today we got it back again, still the same issue. He said he had a hose off somewhere and it showed water movement. He seems a little stumped and indicated maybe some hoses were the issue but frankly doesn't seem horribly confident but since this is still through insurance we are sort of stuck with him.

I'm just trying to aide in helping figure this out. The boat is my dad's baby and was perfect before I essentially killed it, so I want to help as best I can. I'm very mechanically inclined and willing to try pretty much anything.

The only note is this boat also has the VLX gauge package which I have read is very picky, so I don't want to rule out the gauge either. I don't have a meter to laser the temp but could borrow one.

Any help is greatly appreciated, thanks!

 

[Scott Danforth]

change your impeller

overheat is from lack of water flow

 

[Lou C]

Its a good idea to get an IR temp gun, they are not expensive and very useful for monitoring the cooling system. I have found that the area right below the thermostat housing on the intake manifold reflects the engine temp most accurately, its usually about 10 degrees below the dash gauge. Your dash gauge temp should be between 160-175*F. These open cooling systems are pretty simple, they depend on a high volume of water in and out due to the fact that they are not pressurized. Since there was an impact to the drive it is possible that the plastic fitting in the transom mount may have been cracked and is sucking in air. The way to tell is to make up a section of clear hose to put in line with the impeller feed hose and see if there are air bubbles in the water flow when the boat is on plane. The impeller could also have been damaged due to sucking in debris when hitting the shoal. So new impeller and clear hose test, the mechanic should be familiar with this. Volvo published a PDF document "overheat diagnosis" or similar do a search for this it details how to track down overheat issues.

 

[ryankenn]

I'll mention the clear pipe. He did change the impeller on Friday with no change in the issue. I will also see if he has an IR gun to use. I know our gas gauge has always been picky but the temp seemed to work fine.