No one seems to know what is wrong. I just bought an 86' Seaswirl 17ft. bow-rider with the 3.0L OMC Cobra(3.0L GM inline four). The motor was rebuilt 2 yrs ago. The guy that had it before didn't do thing to the motor, assuming that the rebuilt motor was running correctly. I took it to the lake and found that I could only achieve 3400 rpm at wide open throttle(WOT) with the boat empty. It also took about one minute to plane, which it did at about 2800 rpm. When I got back from the lake, I looked in the original manual for the boat, and found it is supposed to operate at 4200-4600 rpm at WOT. Thinking it was the wrong prop, I looked at what was recommended for my boat(13 1/4X19p) and checked what was on the boat(13 1/4X17p). I checked the fuel filter and the points. I replaced the plugs(properly gapped), and checked the timing, only to find it set at about 30 degrees above TDC. I then took out the number 1 spark plug and checked TDC with a screwdriver and it was correct. I then set the timing to 4 degrees above TDC, which is the factory setting for the motor. After tuning the carb, I had it idleling at 550 rpm and it would start first crank every time. Took it back to the lake the next day, and now it wont even start until I advance the timing. Now I can only get 2900 rpm and the motor bogs down when I try to add more throttle than that. After running the boat around the lake, when I return the throttle to idle, in neutral, it revs up to 2000rpm, until I rev it really high in neutral, then it just dies. The motor will only achieve the 4200-4600 rpm it is supposed to when it is in neutral. On the advice of a friend, I checked the mechanical advance in the carb only to find it operates properly and freely. I cannot seem to find anyone who knows what is wrong other than it's probably a really bad engine miss or the timing chain was not installed properly. Any advice or knowledge on the subject would be VERY helpful. let me know If you need any more info.

 

Long posts arent going through

 

Sounds like carb is loading up.

 

(high idle after high rpms)

 

Check timing chain.

 

30 degrees sounds,,

 

,,like 1 tooth off.

 

how do I tell if the chain is incorrect and how do I put it on right?

 

Cam & crankgears willhave timing marks. Marks should lineup at tdc. If not,remove cam gear, correct cam (turn) & reinstall.

 

People on other forums keep suggesting a compression test. Think this is a valid step on a pretty fresh rebuild? The motor has very low hours.