'87 Mercury 45hp Classic 50 losing power

[Happybob52]

After 5 years of flawless operation, my Classic 50 is loo
sing power. It started about 4 months ago, with it bogging down when I tried to get on plane. I would back off the throttle & go again and it jumped right up. Now it's losing power consistently. It won't go over 20-21mph, where it was getting up to 25-27mph. It almost seems like it's starving for fuel, but I can't say for sure. I plan on checking compression this weekend. Any thoughts? I really can't afford another engine.

Edited to say that this boat & motor doesn't sit around for any length of time. I use it just about every weekend throughout the year.

 

[bstig60]

Check Compression, If in spec, you may have a fuel pump problem.... Or a vacuum could be getting created in the fuel tank causing fuel starving. Check tank vent>

 

[racerone]

Check for blockage in the exhaust tuner.

 

[Happybob52]

What and where is the exhaust tuner? I know very little about boat motors, and that's an understatement.

 

[Happybob52]

Checked the compression today. All four cylinders at or very close to 120. I put new plugs in, a new fuel filter, and changed the lower unit oil while I was at it. I forgot to mention in my original post that it starts & idles fine and runs good with the muffs on. Just having the problem when I'm on the lake. I'm going to run some Seafoam through it in the next day or so.

 

[bwguardian]

Probably time to rebuild the fuel pump.

 

[Happybob52]

Ok, I rebuilt the fuel pump on Friday & ran Seafoam in a gallon of gas through it on Saturday. The hoses , connections, and tank vent, etc. are good. Then I took the boat to the lake for a test run. Fresh gas in the tank, just me in the boat. No gear or bait tank. It seemed to run a little better but not great. I decided to fish Sunday morning with my neighbor. It didn't want to run right. RPM's just don't sound right ( no tach, but after 5 yrs. I know how it should perform) and couldn't get over 20mph. on a dead calm water. It always starts easy and idles fine and seems great on the muffs in the yard. Once I get in the water, crap. Are the carbs my next project?

 

[racerone]

Remove lower unit .------Look up into the exhaust passage way for blockage.-----A free inspection step.-----Might install a new impeller while it is apart.