What could cause this

[Bosunsmate]

Evinrude 90hp 1982 4cyl
Bottom right piston is grooved in repeating vertically strips from dome to base on the intake side. Rings are a bit grooved but not majorily like the piston is. Low compression. Cylinder wall is the same but most of the grooves are at the bottom of the cylinder, ie below the intake ports for about half of the cylinder wall. The exhaust side is ok. Piston head and Cylinder head are fine. And yes the wrist pins and big end bearings are fine.
Friend just said it seemed low on power, nothing monumental occurred.

 

[cyclops222]

Looks like my riding mower engine. When I forgot to refill with oil. After a oil change.

 

[Lou C]

Cylinder running lean, what’s the spark plug look like?

 

[racerone]

Common issue with these motors.---Perhaps a plugged carburetor jet.----Perhaps water guides / diverters were blocking cooling water flow and overheating caused this.-----And every one of these motors suffers from broken piston rings.---Shocking what a rebuild costs at a shop.-----That is if you can find a shop willing to do this type of work.-----If you can rebuild it yourself it is worth doing.----Put in 4 new oversize pistons.----New diverters.---Test VRO system.---New impeller.--Will run good for years.

 

[cyclops222]

I compared the cost of a rebuild to a larger better engine.
Mower cut anything now.

 

[Bosunsmate]

Cylinder running lean, what’s the spark plug look like?

Same as the others curiously. But the outside was rusty unlike all the others, probably incidental I'm not sure. Thanks

 

[Bosunsmate]

Common issue with these motors.---Perhaps a plugged carburetor jet.----Perhaps water guides / diverters were blocking cooling water flow and overheating caused this.-----And every one of these motors suffers from broken piston rings.---Shocking what a rebuild costs at a shop.-----That is if you can find a shop willing to do this type of work.-----If you can rebuild it yourself it is worth doing.----Put in 4 new oversize pistons.----New diverters.---Test VRO system.---New impeller.--Will run good for years.

Heres the diverters, ive no idea how they work but is this an example of blocked? The other side matches this one too but has a slight open channel still. This photo is from the gouged cylinder side.
Yes Il rebuilt it for my friend, shops just want people to buy new is my experience these days. Thanks

 

[Bosunsmate]

I compared the cost of a rebuild to a larger better engine.
Mower cut anything now.

Haha hopefully that means bamboo too

 

[Lou C]

Looks like that calcium build up might be causing a hot spot?

 

[racerone]

Clearly that diverter is blocking 93.5 % of the water flow around it.----And water does NOT go through that diverter hose either.----A factory manual would have a flow diagram that explains it all.

 

[cyclops222]

Bosumate appears to be a saltwater boater. That motor may be severely loaded with salt deposits from the ocean. Bay of Islands, New Zealand.

 

[Bosunsmate]

Bosumate appears to be a saltwater boater. That motor may be severely loaded with salt deposits from the ocean. Bay of Islands, New Zealand.

Yep a saltwater fisher too like Zane Grey did here. He probably got around here with an OMC at sometime as well. Thanks for all the insights, good to know what likely caused it. Yes The salt water here is so warm for a lot of the year that barnacles will make your hull feel like 60grit within a few days. Ive got a manual that shows the water restrictors flow and definitely its what mine wasn't doing. The manual doesn't have all the info I think il need so il likely be back asking for more. Way nicer and better than youtubing it

 

[jimmbo]

VRO didn't come out until 84

Only the Intake Side is scuffed/Scored, and the Exhaust Side is Fine?

 

[racerone]

Oops----Missed that it was a 1982.-----But that is CLASSIC damage found on the V-4 and V-6 crossflow models.

 

[Bosunsmate]

VRO didn't come out until 84

Only the Intake Side is scuffed/Scored, and the Exhaust Side is Fine?

Yep correct, exhaust side is supermodel woman smooth all over. The diverter tube was so swelled on the intake side i dont know how water managed to get past it ( or if any did) The guy who I'm getting the new pistons from said the diverters don't go the whole way to the end. The diverters this had seemed seated at both ends. There's a little hole at the far end of where the diverters go which seems to interconnect a water channel at the rear of the cylinders on both sides which would be blocked by a full length seated diverter so I'm not sure how to deal with that. The manual doesn't mention it.
Il have to check the temp sensor too