Hello, <br /><br />I have been readin this board for a few years, and as my first boat had a 85HP Force I found the info, advice, and insight very valuable. I always found what I was looking for, and so I never posted. I have upgraded my boat, and I am having a problem I cannot find a post covering.<br /><br />1990 5.7 Mercruiser 260HP. I bought the boat in April of 2004. First time I put it in the water top speed was 49MPH according to the in dash speedo. I do not recall what the RPMs were, but I know it was over 4000 because I remember thinking that is a high number for a 5.7. The second time we put the boat in the water in noticed it running hot at idle (180 to 220) but it would cool down at crusing speed (140 to 150). I thought it was the impeller. I called a couple of shops in the Dallas area, and selected one based off of the confidence level I had in the individuals I spoke with over the phone. Shop pulled the lower unit, found a damaged but not destroyed impeller as well as some damaged bearings and a drive shaft. I told the mechanic who is also the owner I did not want to have any problems out on the water, so please give the motor a once over to see if we can catch any thing. He ended up replacing the impeller, damaged bearings, damaged shaft, shift cable, lower unit lub and motor oil. To the tune of about $1,500. I picked up the boat and I added Bennent trim tabs. <br /><br />I put the boat in the water, and now my top speed is 40 MPH at 3,500 RPM. I called the mechanic and told him of the problem. He said bring it by. Today I took him the boat and he looked at the motor and the outdrive. Asked me if I had changed props, I have not and told him so. He did some math and discovered at 3,500 RPM the boat should go 41 MPH but at 4500 RPM where the motor should redline the speed should be 51. Asked me again if I changed props, and again I replied no. He then asked me if he had replaced the exhaust flappers, and I did not know. He pulled the ticket, no flapers replaced. Told me I would have to leave it as he could not look at any more today. Anyway, I am spending a week at the lake next week, and I would like to take my boat, told him so, and I asked if I would hurt the motor if I ran it in the present condition. He said it might burn a valve. His best two ideas is that someone had changed the prop or that one of the flappers had broken loose, fell down the exhaust system, and is blocking the exhaust. He gave me two gaskets and told me I could pull the exhaust apart to see if the flappers are in place. I took the boat home, pulled the hoses, and found two very worn, but, but whole and in place flappers. It appears the flappers never close, as if all of the spring is gone out of them. Now I am at a loss. <br /><br />What is causing my loss of RPM and speed?<br /><br />Will I hurt the boat by driving it when it is not preforming at 100%?<br /><br />Is the mechanic attempting to pull a fast one on me? <br /><br />Do I need to get a second opinion?<br /><br />Thank you
