'98 larson with 5.0 gl I/O. overheating

[Dustin110]

Been reading over everyones forums for the last couple days trying to figure out why my boat overheats. Im just starting to look into it and have not done anything to it yet. It seems to get hot at idle while in the water...but not with muffs on. At rpms > 1500 it seems to maintain temps at 175....whether im on plane or just revving the engine up. I have had problems with it in the past with the cylinders getting hydrolocked....which took me pulling the plugs and spinming the water out of the cylinders a mechanic took the exhaust apart and did not see any obstruction...i believe he changed the timing slightly as well...mentioing this may be causing the problem....at any rate the motor seems to rundecent but i still have this issue of the motor getting hot...esp at idle. i was going to start with the thermostat and inspect for forien materiak then overall insoect for any possible air entrai.ment on the prewater oump side of thing....just so u know im newer to working on boats so please allow some explanation with terms. and pardon my typos...not so smart phone friendly

 

[Dustin110]

Re: '98 larson with 5.0 gl I/O. overheating

And thanks for any advice!

 

[Maclin]

Re: '98 larson with 5.0 gl I/O. overheating

Welcome Aboard!

Sounds like it is due for an impeller replacement in the raw water pump.

In the Adults Only sticky a the top of the forum you will find a link to Volvo Penta information, then under that you will find a link to a site where you can search for and download an owners manual for your engine and drive, and it should have the instructions regarding servicing the raw water pump.

 

[bnicov]

Re: '98 larson with 5.0 gl I/O. overheating

Start by checking the impeller to see what condition it's in, if you haven't changed it in over 2-3 years, it's defintely due for replacement. Also, check the thermostat housing for bits and pieces of impeller, check all the nooks and crannies in it. There is a section on dealing with overheat conditions in the correct manual for your engine. Go through each and every step.

 

[Dustin110]

Re: '98 larson with 5.0 gl I/O. overheating

Thanks. Had the boat since new....never been changed. Ill get to rippin it apart. Do you think I need to pull the thermostat as well?

 

[Maclin]

Re: '98 larson with 5.0 gl I/O. overheating

A worn impeller causes the exact symptoms you described. Once you remove and inspect the old one, if there are pieces missing those went somewhere and you need to flush them out before installing the new impeller. That may involve removing the thermostat if they jammed in there. But if no pieces are missing and it is just worn down then my opinion is that is your problem and the new impeller should fix you up, no need to go after the Thermostat yet.

 

[Maclin]

Re: '98 larson with 5.0 gl I/O. overheating

"Had the boat since new....never been changed"

Dang son, were you trying to kill it?!?!?!

 

[Dustin110]

Re: '98 larson with 5.0 gl I/O. overheating

Split the pump housing (ultra simple btw) and yea the impeller is worn down real nice like. In defense its my dads boat but at any rate Ill be sure to read over the scheduled maintenace from now on. Wish I knew how to upload a photo. There was on piece that was jammed in the inlet piece right before it leaves the housing. Ill flush then take er for a ride. Thanks again for the guidance!

 

[bnicov]

Re: '98 larson with 5.0 gl I/O. overheating

Put together the pieces like a puzzle, if you have all of them, you won't need to backflush the cooling system. If you are missing a few bits and pieces, you'll need to flush it out to get them out. Impellers should be changed every couple of years to avoid these issues.