i have an 87' larson with a 5.0 that i bought in april of last year. the boat has been layed up in a marina since 1995 till i bought it for a song last year. to my knowledge (from talking to people who were familier with the boat and the last owner) the boat has very little hours on it. i ran the boat pretty much all last season without a problem until i caught a bag on the outdrive and cooked the waterpump & impeller. it was professionally replaced by the marina i bought it from in the offseason, along with bellows, shift cable and gimble bearing. the begining of this season i changed the plugs, oil, wires, and cap, which i believe were all original. motor ran great, but, at high rpm in gear the motor wanted to run at around 200 degrees. i would back off the throttle and it would go back to normal, which is about 170 degrees. okay, lets change the thermostat, original, 15 years old. same problem. lets change the water circulator, original also. that was bad, had some cavitaion. after replacing i noticed at idle engine would run cooler than usual. when i would run the rpm up higher at idle it went even cooler. i was happy at that point, but, with it in gear i had the same problem. it wouldn't go into the red zone, but it was very close... throttle back and it went right down to normal. next thing, risers. started engine and put both hands on both risers, one was warmer than the other, hmmmm... like the curiosity that killed the cat i removed the hotter riser only to find a hole on the inside about the size of a dime allowing water to go into the exhaust manifold. i'm thinking this is most likely my problem. i have ordered new risers and they should be in soon. the manifolds themselves don't look in to bad of shape, but i will remove them and have them steamed out and check for cracks, but will change them next year. if anyone knows of anything else i should check, please let me know.<br /><br />thanks
