2003 Mercury EFI 2.5l 200HP OT749297 with 23 balistic prop
I have been having some trouble with this engine that I recently purchased. The seller said that one of the cylinders is having a blowdown issue on one of the cylinders. So I decided to rebuild the motor which was done a mechanic in Bradford, Ontario Canada.
I have been having power issues where I can't get it up over 2000 rpm but will rev up over 2000 rpm in idle.
After taking it back to the mechanic last time, he said he changed the plugs and that I was still in the 2hour break-in and that I needed to drive it harder as I only had about 1/2 hr of 1.5 hours above 2000rpm as the boat initially performed fine after the rebuild.
He changed the plugs, I took it back to the lake and initially was able to get to 3000rpm but still the same issue.
I was 4 hours from the shop, so I drained the tank as I had put some regular 87 octane gas in it. Once drained, I put yamalube ring free and approx 50 liters of gas. The boat started up right away so I figure this is a gas issue.
I then filled up the boat with premium gas from Esso 91. Drove it in lake Huron, probably down past 1/2. Open lake so easily 30-minute jaunts at over 4000rpm seemed to run quite well.
Last weekend, on the way to six-mile lake, Ontario, I filled it up with Shell Premium Nitro 94 gas, no ethanol, in Orillia. (also added a 350ml tube of yamalube ring free)
Drove it Saturday and Sunday without issue. then Monday at 1/4 tank, same issues. loose power, won't go above 2000 rpm. Revs high in neutral. Went to the marina to add another 50litres of gas to make sure gauge wasn't wrong but no luck, the same issue.
Gas bulb seems firm.
Is this the EFI or efi cleaning needed?
Any other suggestions?