Challenger 1800 Worn Rings

[Jdmak13]

Its spring time so im back for more questions. I took the top end off of one of the engines in my 1800 (787) because of low compression problems. The pistons have no sign of wear at all nor doo the cylinder walls, not even a scratch anywhere. I havent got the chance to measure the bore yet but is it possible with no signs of wear that they will be out of wack? should the bore measure 82 at all points in the cylinder bore? Im hoping i can get away with just reaplacing the 14 year old rings.
My next question is im wanting to add another battery with a 1/2/All switch. do i need two switches for the twin 787's to run 2 batteries? Does anyone have a suggestion where to mount the second battery in the challenger 1800? i dont think there is room next to the original. Sorry for the long post i just want to get this going soon!

Josh

 

[Jdmak13]

Nothing? No insight?

 

[Dennis]

I don't know about the battery situation. How low was the compression? I 've never seen a Seadoo yet that had low compression and not have cylinder/piston scoring. Unless the rings were just stuck to the piston from sitting.

 

[howie099]

more than likely after you hone the cylinders you will need the jugs bored. On the Switch you use just 1 for both engines all the electrical connections go to the common post and the the batteries go to the 1 and 2 post. I seen people mount the 2nd battery on these boats in the passenger compartment.

 

[ialonso]

more than likely after you hone the cylinders you will need the jugs bored. On the Switch you use just 1 for both engines all the electrical connections go to the common post and the the batteries go to the 1 and 2 post. I seen people mount the 2nd battery on these boats in the passenger compartment.

What gauge did you use? I borrowed some gaguges from Autoparts and all gauges read differently and all out of whack.

Do you see a performance difference in the engine? What does it do?

replacing the rings is cheap. If the boat is running maybe try it for this season and if it fails, then in the winter do a top end?

does adding a little oil to the cylinder improve the compression reading?

 

[Jdmak13]

The reason i started digging into the top end was because last year i would go out and be able to run the boat as much as i want, but when i shut it off the one engine would never start back up in the water. i did a couple of tests where i would go drive around for like a half hour and come back to the launch and shut it down. to no surprise it would not start so i just figure the compressing is too low to get the engeine started in the water. I then proceeded to put it on the trailer and pull it out and the second i got it out it would fire right up. the compression was around 120 on one cylinder and 126 on the other

 

[Dr Honda]

Sorry I missed this... but hard restarts can be caused by

1) a leaking needle and seat in the carbs
2) Bad crank seals
3) Fouled spark plugs
4) some electrical issue

So... assuming low compression was bad. Also... with any gauge... you need to verify it with some other method. Even though 125 is getting low on an 800 engine... it should still run. (it just won't have good top end) By any chance, did you check the "Good" engine?

I know this may sound basic... but I've seen people rip apart perfectly good engines because the O-ring on the gauge was bad, and they read low.


OK... with all that said... Yes... the rings could just be warn out. It's normal to see on the 720 and smaller engine... but normally, something else happens with the 800 to kill it at the end of life. It's just how they are since the HP is so high for a 2 cyl engine.

 

[Jdmak13]

when i had the problem last year i took the carbs apart and cleaned them well and the problem persisted. I then changed spark plugs numerous times to no avail. I have inspected the cylinders closer now that i have the top end off and around the bottoms below all the ports there are some very small vertical ridges. Being a 14 year old boat with the engine never being touched i figured i would have to start doing these things eventually. I just dont get why it will not start for the life of it in the water after shutting it down after the initial run and sitting for 5 or more minutes, but i can pull it out and it will fire right up no problems at all

 

[Jdmak13]

Another question... when i took the top end off there was a lot of oil down in the crank case, should this be the case? it never smoked or anything in any way.

 

[ialonso]

Humble suggestion: Try this

I would venture to guess your issue is fuel related. I never succeeded in properly rebuilding my carbs. I am lucky that my engines use 1 carb each. I just bought new. I've done it twice, never looked back.

What is your rutine for powering up those engines after that 5 minute pause?

If it's a leaky seat, or some problem in the carb causing a fuel leak, cranking at full throttle should result in a faster starting engine. Try one more time, and when it does not restart, do NOT use the choke, and instead set and leave the lever at full throttle while you crank. If it starts much more quickly, it's the carbs. (The extra air offsets the extra leaky fuel, and the motor starts once it;s no longer "flooded.")

I added a spin-on filter in replacement of the seadoo filters to increase my fuel quality before reaching the carbs, and that has served me well in lengthening the life of the carbs.

 

[Jdmak13]

Ok i lied there was not a lot of oil down in the crank cases. just a minimal amount probably fogging oil from when i put it in there. But my starting procedure consisted of opening the throttle all the way because i also thought it was leaky needle and seat. when tnat wouldnt work i would try just starting normal and then with the choke. i just dont get why it starts right when i pull it out of the water but not in the water. then it would start when i drop it back in.