Seeking Advice on 1996 Seadoo Challenger 787 Engine Repair

[Jeff Konieczny]

Hi Everyone,

I have a 1996 Seadoo Challenger that has been used exclusively in fresh water but has been sitting for the last 4 years. Overall, it’s in good condition, except for the fact that one cylinder has 120 psi, while the other has only 60 psi. There’s good spark, and the engine seems like it wants to start. Other than that, I don't have much history of the machine.

I’m wondering if I should purchase a top-end rebuild kit (about $400 CAD) and attempt the repair myself, or if I should invest $3000-$4000 for a mechanic to do a complete engine overhaul.

What would you do in my situation?

Thanks for your input!

Best,
Jeff

 

[burtshaver2021]

Your situation would depend on a few things, do you plan on ever rebuilding another engine? If this will be the only rebuild you ever attempt then I would probably just sell the boat and buy a running one. You should be able to purchase a good running one in the 3000.00 to 4000.00 range. There would be very few mechanics I would trust to work on my seadoo’s. As a matter of fact I find being a mechanic is a detriment in a lot of cases because they feel they already know everything there is to know and dive right in missing a few important elements. If your planning on possibly wrenching on a few motors in the future then I would definitely go ahead and rebuild the motor yourself. If you do rebuild the motor you are going to need to find a good machine shop that can bore out the cylinders to the next size, you are going to need a good quality outside micrometer for measuring the bores and pistons, i purchased 2 Mitutoyo outside calipers but you will only need one to start. Your going to need a dial bore gauge to measure the inside of the bores, a means of pressurizing the engine to check the inner and outer and crank seals ( I use a Mityvac that can apply pressure or vacuum). I would actually make this the first thing you do before buying any parts or tools is to do a leak down test on the crankcase to see if it’s even worth proceeding. If the inner crank seals are bad and you need a new crank you may decide it’s not worth the time and effort for this motor. Other than those tools, the only other sort of specialized tools you will need is a torque wrench, a set of chases I believe they are called ( not sure on that, I have them but can’t remember what they are called lol) but anyways you will want to clean out the blind hole threads before rebuilding, a straight edge for checking trueness of cylinder cover and cylinder mating surface, some feeler gauges for checking that and for checking ring end gap, a piston puller for removing wrist pin, ( the one I have doubles to intall the circlip at t ends of the wrist pin ( on skidoo anyways ). Maybe a file set if your going to be chamfering there porte yourself? Or best if the machine shop will do it, I find the plastic razor a rappers handy and liquid chisel I believe it’s called for removing gaskets, little brass brush again for cleaning up mating surfaces. You will need a pop off tester as you really should rebuild the carbs and the Mityvac comes in handy for checking for leaks after carb is together and for checking fuel pump at 4 psi ( no compressor air here lol ) I’m sure I’ve forgot something but this will give you an idea anyways. Let us know what you decide,

 

[Jeff Konieczny]

Hmmm... the youtube videos on top end rebuild did not include all those measurements (that I saw just now in the service manual). Is it easier to buy a rebuilt engine and replace it? Is that something that can be done by a (reasonably handy) noob? Would a new engine pretty much just require the tool for aligning to the driveshaft (which is rather expensive)? Would a new engine also require a new rotary valve and re-built rotary cover?

 

[burtshaver2021]

I seen your question and reply in the other post where you were advised that by keeping track of the shims the alignment tool is not required. I will admit that I have done the same, remover engines and put them back exactly as they were with same shims in same spot with no issue, but with a rebuilt engine I would recommend using the alignment tool.
Yes a Noob can remove and install the engine himself and a Noob can also rebuild the engine himself.
I’ve never bought a rebuilt engine from anyone, I would think if your getting one from a reputable company the rotary valve cover would have been inspected and machines if required but you could always ask. I’ve heard lots of bad things about SBT and SES. If I were buying a rebuilt engine it would be from Peter Rusinski out of Illinois I believe. Can’t think of the company name right now.

 

[Jeff Konieczny]

Thank you so much for your help! I haven't made a firm decision, but I'm leaning towards paying the $3000ish to have it done by an experienced marine mechanic. It will probably end up costing about the same as buying a different boat (that runs). But if I have it rebuilt, at least I know that it is a fresh engine! I was also reading about some negative experiences with SBT and SES. I'm guessing Peter is at All-Marine Motorsport just northwest of Chicago?

 

[burtshaver2021]

I believe Peter owns Fox Valley Powersports and that would be my first call. I would be asking the marine mechanic how many of these Rotax engines he’s done, what he plans on doing? Crank? He needs to be doing a leak down test on this engine, need to know what caused the great difference between cylinders, where is he having the machine work done? If he’s simply dropping a new set of pistons and rings in 3000.00 is way to high, actually even with machining 3000.00 is pretty high IMO, boring and finishing if the cylinders should be 150.00 max per hole, possibly as little as 100.00 with 800.00 in parts 2200.00 seems like enough to be doing the work. Id he removing and installing the engine? Will he be using an alignment tool? Anyhow, I’m just saying know what your paying for.

 

[Jeff Konieczny]

Great advice, Thanks again! I'm near the UP in Michigan, so it's about an 8 hour drive there. A long drive but would be worth it for a good mechanic.

 

[burtshaver2021]

Great advice, Thanks again! I'm near the UP in Michigan, so it's about an 8 hour drive there. A long drive but would be worth it for a good mechanic.

Your so lucky,?good snowmobiling there usually. Best of luck whatever you decide. Fox Valley Powersports will ship it. I would at least check out there pruning if you go that route. They do hundreds of them and from what I hear go above and beyond so that’s why I keep recommending them

 

[Doug Overkill]

I often tell people If you are going to own a 20+ yo high performance 2 stroke anything you will need some mechanical skills and develop more while adding tools to the box. Wether that is a jet boat, jet ski, snowmobile or other it will require virtually constant upkeep. It’s the nature of these performance engines running close to optimal all the time. That said it is very doable for those with desire and some skills and the ability to learn.

The huge bonus is sites like this and the fact that nearly all of the issues you will have are answered. I keep a 3-ring binder with all sort of specific notes about my 1997 Challenger 1800. Print out threads and highlight issues and solutions so when they come back the answer is there. Also when you solve something that you asked about here, PLEASE come back and post a follow up. It helps everyone.

If you don’t want to wrench on a boat then a mercruiser 3L maybe better suited. Here in the northeast there aren’t many/any marinas that will work on these 25 year old boats.