Good day, I have a 1996 XP with a 787 engine. It starts fine on the hose and will rev up easily but as soon as it's in the water it will start harder and won't rev up at all will just sit and idle, as soon as I try to rev it wants to die. When I bought it it was doing it found sleeves where bad so had them rebored to 1mm over and did the top end but is still the same afterwards. Compression shows 90psi but is a cheap gauge so not even sure if it works. Checked rotary timing, replaced spark plugs, redone fuel system, converted it to premix, cleaned the carbs, squish is 1.4mm. Don't know what can be the cause, don't want to rebuild the carbs if not necessary because I live in South Africa and Makuni kits are hard and expensive to get. Any help will be highly appreciated. Attached a zip file with a video if it helps.
787 not revving up in water
- Thread starter JPDeKlerk
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- 787 800 seadoo
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Tested the compression tester with my air compressor, set the regulator at 90psi and the gauge showed 85psi so going to assume for now the gauge is fairly accurate. Tested the compression again with no airbox or fire arrestor at full throttle and both showed 85psi, assuming the gauge is correct for now what can cause the low compression? Has brand new WSM pistons, rings, sleeves was bored and honed to spec, squish is 1.4mm, new top en gasket set. Checked the rotary timing also as the manual states
Ckrawiec
Well-Known Member
Let's be blunt....the ski is 25 years old.
Assuming the low compression issue COULD be overcome.....the fact that the machine will run and rev on the hose but want to BOG and die in the water (which is a full load condition)....you are staring down the barrel of the carbs being the issue (most likely). Cleaning them will only get you so far.....rebuilding them should get you the rest of the way [follow the Carb rebuilding sticky post]. The carbs are very persnickity....rebuilding to original specs ALMOST always is what is needed. I've been in your shoes....so experience dictates. Good Luck.
Assuming the low compression issue COULD be overcome.....the fact that the machine will run and rev on the hose but want to BOG and die in the water (which is a full load condition)....you are staring down the barrel of the carbs being the issue (most likely). Cleaning them will only get you so far.....rebuilding them should get you the rest of the way [follow the Carb rebuilding sticky post]. The carbs are very persnickity....rebuilding to original specs ALMOST always is what is needed. I've been in your shoes....so experience dictates. Good Luck.
Thanks for the help, thought the same on the carbs just didn't want to get rebuild kits if the compression is still low. Went over the rotary assembly again, timing was in but measured the wear with two peaces of solder wire and found the gap between the cover and the engine with the rotary valve in place is 0.45mm to 0.47mm and the manual states it must be 0.30+-0.05mm. Will that excess wear cause the low compression and hard starting?
Ckrawiec
Well-Known Member
Based on your measurements, this engine is how shall we say it -> "worn in". It appears to be out of the tolerance limits and sounds like it's "leaking" compression/exhaust (i.e. -> power).....so, as sad as it is to say....she may be past it....now back to the 25 year old ski equation.....can you rebuild it back to tight tolerances....ehhhh MAYBE....BUT is it worth the time and effort???? Only you can make that call.....sometimes you have to/should let sleeping dogs lie!
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