Volvo 8.1 GI overheat

[Frankg158]

I have a 2001 Chris Craft 25 Launch with a Volvo 8.1 GI and duo prop outdrive. During our first day out for the year (and after several months in the shop during covid for seasonal service) the outgoing cooling hose came loose from the raw water pump and the engine overheated. Towed back and a couple days later I go back, hook up the loose cooling line and hook up to water to test and see if I burned up my new impeller and as she turned I heard a heavy metal on metal knock. It couldn’t have overheated for more than a few minutes and I’m looking at a significant repair bill for one loose screw. What could have happened inside my block? Is my mechanic to blame?

 

[Scott Danforth]

welcome aboard

you would be hard pressed to blame anyone except yourself for your pre-boating check

it doesnt take long without cooling water for a motor to over-heat. which not only burns up all the rubber bits in the exhaust because you now have 1200 degree exhaust blowing across rubber that melts at 250F, however the motor expands and things like pistons and bearings eat themselves.

 

[alldodge]

Howdy
If you paid to have the motor readied (summerized) to go, then the shop would be on the hook, if it was just pickup then not so much

The overheat with no water in the motor can do all kinds of things and none of them good. Since your hearing a knock then its probably a rod bearing and the motor needs a rebuild

 

[Frankg158]

It’s a bummer because I did pay for an extensive seasonal service to get ready for summer. I got the boat back a few weeks before we took it out. All that aside, what should I expect to pay for a rebuild due to overheat or is it more cost effective to get a remanufactured unit? Any ideas on the labor hours to rebuild vs swap a long block?

 

[alldodge]

If you do the rebuilding it will be less to do yours. If you have yours rebuilt it may be the same price as buying reman

 

[Scott Danforth]

its $13k for a new 8.1 longblock

its about $6k for a remanufactured longblock

its about $2500 for parts and machine shop labor to rebuild it yourself.

if you have to pay to have the drive pulled and the motor pulled, that would be extra.

 

[Frankg158]

Thanks for the numbers. That’s about as frightening as I thought it would be. I don’t have the experience to do this kind of work myself I don’t think. Wondering if you guys have any thoughts on preference between new and remanufactured? Also wondering for this year of Volvo, is there supposed to be a safety shut off for over temp on the ECM? The way it happened it was so fast and no warning after a day out on the water.

 

[alldodge]

There would be an alarm and reduction in power but not a shut down. Not hearing an alarm, I wonder if its disconnected?

 

[Frankg158]

Neither of those things happened during the overheat. I’ve switched mechanics and it’s in for diagnosis and repair to see if we can salvage this summer. Thanks for all the help.

 

[Scott Danforth]

Thanks for the numbers. That’s about as frightening as I thought it would be. I don’t have the experience to do this kind of work myself I don’t think. Wondering if you guys have any thoughts on preference between new and remanufactured?

Personally, depending on the boat, I would rebuild myself or in your case, take to a really good machine shop locally.

the first thing I would do is a good diagnosis to determine where the issue is - broken piston, or rod bearing are the two likely culprits on the 8.1

then if needed, a tear down and inspection

if it needed a full re-build, then I would probably go .030 over on the pistons if the rough bore cleaned up to that, buy SCAT rods (cheaper than reconditioning the stock rods in most cases) and for the crank.... $322 buys you a brand new GM crank. usually that would be cheaper than re-conditioning the existing crank.

then spend the extra $300 for coated bearings

since you have a pre 2004 8.1, i would convert to floating wrist pins which would require you to buy new rods anyway.

for machine work, a line-hone at a minimum, re-size the mains, then true up the deck, and minimum over-bore (the .030 stated prior)

 

[Frankg158]

Update on the saga. Port side cylinder bank was full of water when they pulled the plugs and after a dry out it turned over and purred like a kitten. He is thinking I can get out of this with a valve job and not replacing the engine for, get this, 18k for a reman 8.1. Also, he found the boat does have an audible alarm that is not functioning and was looked over by the previous mechanic for 2 years straight. Would have saved me a bunch of money. He is going to tear it down and inspect to see if we can complete a valve job, but it sounds like there is life in the motor.