US-1, what i found so far........

[Talon2.5]

ok, as you remember i was thinking it was the mid-plate, it ran 130 degrees at an idle and 170+ at around 4 grand.

pulled the lower unit first, looked in where the tube goes, the rubber seal in the pump was half gone, tore apart the pump and all the gaskets were wet (there usually dry and stuck to the housing), pump housing upper and lower were warped a bit, pulled the brass tube out (which i never checked when i bought this motor) and it was bent, looked up inside with a flashlight and the rubber seal at the top was good, so redid the pump with another impeller and used some other pump parts and new gaskets, new water tube and rubber seal in the pump, made sure while the pump was apart that there were no restrictions in the bobs nosecone set-up and put it all back together.

i also changed the plumbing on the pee tubes, i now have one off each head and one off the poppet cover, the reason i did this, which i'm sure you know is to monitor water from the highest cylinder (#1)as well as the other side.

took it to the ramp, i always noticed that this 2.5 i bought didnt seem to sound very throaty at an idle and with the exhaust chest milled out and the exhaust port work i did the factory settings on the idle timing wont work, so i fired it up and fine tuned it in and finally it idles around 100 degrees on the guage, used my laser thermometer and got 109 temp readings on the cylinders and lower, and good flow on all three pee tubes.

today i am taking it to the lake to run it and will post those findings later today or tomorrow

thanks guys, skip

[us1]

From the sound of the shape of that rubber grommet on the bottom of the water tube, it sounds like you fixed it.

[Talon2.5]

success.....she runs 140 degrees, pumps water good and cools right down, but, for some reason the volt meter has been pegged out since i put this motor back together and it didnt do that before, i suspect the rectifier it doesnt have a regulator what do you think?

skip

[us1]

I cant think of any thing that would peg the volt meter. Does it do it with the motor off and the key on.

[Talon2.5]

no it reads 12 volts with the key on and motor off and when ya fire it up it reads 12 but as you drive it it slowly goes up and maxes out, it used to only go to13 or 14, on all the mercs ive had this is the first one to do it, and this is all the electronics from the 2.5 that i blew up and it all worked fine before and did not peg the guage so i'm at a loss here, the only thing that i could think of was the rectifier and i get some that say no and some that say yes about that rectifier and i dont have a spare one, but i guess i'll get another one to try it.


thanks!! skip

[us1]

I think its possible it’s the rectifier. If your tach works properly now try switching the gray wire on the rectifier to the other terminal with a yellow wire on it. Check tach again and see if it still works properly if it doesn’t the rectifier is bad. Its possible to do ohm checks across each of the four diodes in the rectifier, you should get 112K ohms one way and 240K ohms the other way, I am going by memory now but I think that is right.