Newbe needs help with a 787

[Yuba Jim]

Guys, Thank you for this forum, I have learned a lot by reading the trhreads, Now I have a question I hope someone can answer. I bought a 1996 Challenger with the single 787. The previous owner said he had rebuilt the engine and it ran well and looked good so I bought it. I took it to the lake it and it planed quickly and ran great. Then a little while later I couldn’t get it up on plane. I looked around and found that the hose coming from the water regulator and going to the exhaust had come off at the regulator. I re-attached it but it made no difference, the boat still wouldn’t plane. I looked around again and saw that the same hose had melted at the exhaust end when it got hot. Because of the way it was routed it was lying on the exhaust. I also noticed that the formerly purple pipe had turned brown. I cut the melted end off of the hose and re-attached it. Again, the boat would not plane. I lifted the engine cover and observed while running that the water regulator was leaking. The faster I tried to go the faster it spewed out water. I couldn’t find a good used regulator so I bit the bullet and bought a new one. Again, the boat wouldn’t plane. I did a compression test and found that both cylinders were at 110 psi. While at least even, that sounds pretty low for a Doo engine that supposedly has just been rebuilt. Everything I have read indicates that the amount of water coming from the regulator is so precise that even an incorrect fitting can cause severe damage. So my question is what actually gets damaged? Did the heat make the engine tight? It runs good and it revs well, I suspect it just isn’t making the power it should. When I am able to get it on plane - by going around in circles until it climbs up – it still tops out at 42MPH. It should be able to hit 50 shouldn’t it? One thought I had is that when the guy rebuilt the engine he used too thick of base gasket and that kept the compression low, but if that were the case why did it jump up on plane so well the first time? I have to think the heat did some damage but what is the damage and what is the repair? Anybody got any ideas. Thanks

 

[seadooya]

I suspect, that the pump is the culprit. It was not producing the volume, that the system (motor, regulator..etc) needed, for optimum performance.

Inspect the pump assy, its VERY easy to injest dubris, if not noticed in the water. Aftre inspecting, post back.

 

[Yuba Jim]

:agree: Thats about right. Thats a good idea. What am I looking for? Just debris or something else.The wear ring and impeller are new and I installed a new foam ring where the pump goes into the hull. The old seal just disinigrated when I pulled the pump. Now that you say that I seem to recall reading somewhere that some models had an extra or different neoprene ring. I wonder if I am missing that. Basd on what you're saying that sounds like it could be it. So your not overly concerned about the 110 PSI or the heat that the pipe got when the regulator should have sent water to it? Thank you for your help, I apppreciate it.

 

[seadooya]

howd it turn out?

 

[Yuba Jim]

I haven't taken it out of storage yet. I will will be getting it out in a few weeks and I will check out the pump. I think you are onto something there. Thanks for your help