Re: service manual
Boat is 1984 bayliner capri 19.5' bowrider with a 1990 Yamaha 115HP outboard.<br />Motor was rebuilt last fall. New pistons, rings, water pump, gaskets, carbs rebuilt, new 21" prop. The oil injection was taken off but the little bottle was left on the motor with oil in it to stop an alarm that was going off intermittenly. I had a 2stroke 9.9 that I was running off the same gas tank and that was the main reason for getting rid of the oil injection. On the test run, the motor started fine, ran smooth and quiet, and smoked a little. When putting the throttle down though, it would run up to 3900-4000 rpm and then start to stutter and rpms would fall off to 3000rpm. I would then have to back off throttle and then gradually ramp it up to 3000 rpm, approx. 20-23 mph.<br />My friend went for a ride with me and he pumped the primer ball by hand while I had the throttle down and we got up to 4500 rpm smoothly and held it until he couldn't squeeze the ball anymore. He then put new hoses and primer ball on and put a new rubber diaphram in the fuel pump.<br />He ran boat and it seemed okay then problem started again.<br />I changed prop to 19" and boat got up to 5000 rpm before stuttering and dropping rpms again. Now it would run steady at 3500 rpm but only do 23 mph. I took it up north to an inland lake to ski and fish with. One day the water was like glass and I pushed it full throttle. The boat jumped out of the water and hit 5200 rpm at about 42mph but only for about 15 seconds and then it started stuttering again and I had to back the throttle off to nuetral and bring it back up to 3500 rpm to smooth out the ride. That was the most I had ever seen out of the motor.<br />One thing that bothered me, was the gas that leaked in the water when we were sitting still. My friend saw that the little oil bottle was nearly empty and thinks it was leaking into motor causing the smoking and gas stain on water.<br />As I mentioned earlier, I tore the water/fuel separator apart and it was clean as was gas that dumped out. All hoses were clean and not pinched anywhere. The boat runs good at low rpm so I don't think there is a major problem but it sure is frustrating me as I have never worked on marine engines before and don't know where to look.<br />Your vacuum test sounds like a start but I do not know where to hook it up to test.<br />I sure would appreciate any help. One last thought: the boat had a new transom put on and it was raised 3-1/2". My friend owned the boat prior to me and had no problem with this height with the same motor on it. Could this affect it when it gets up on plane.
