2006 Mercury Optimax 175 issues

[rezenification]

I am at a loss. I recently bought boat at auction that came with a Mercury optimax 175 outboard. It fires and idles great on the trailer with muffs. I made a tank to lower the outboard into out of a old 80 gallon pressure tank to try and test the motor as the lake is an hour away. the engine revs to 5k plus no problem in gear in the tank. when I go to the lake it maybe gets to 4k the first attempt to get on plane, then revs less with each consecutive attempt. after 5 attempts or so, it struggles to even start. I have checked fuel pressure and air pressure while it is on the trailer and both are where they should be. I have changed the fuel filter, fresh 91 octane fuel. both oil tanks(main in the boat and engine mounted) are full. Spark plugs look good. Any help would be greatly appreciated as I don't have the funds to take it to a shop. Thanks!

 

[flyingscott]

That's a bad motor to not have the funds for as parts are generally expensive. First thing to do is buy the factory manual. You need to see if it is storing any codes. But a good bet is the motor is the reason it ended up at auction.

 

[rezenification]

That's a bad motor to not have the funds for as parts are generally expensive. First thing to do is buy the factory manual. You need to see if it is storing any codes. But a good bet is the motor is the reason it ended up at auction.

It was at auction due to being to close to a fire. I assume a building fire. The gel coat was damaged on the bow but the fiberglass didn't have any delamination. I've already redone the entire side of gelcoat and copied the original glitter work so it looks great again. It's not that I can't afford parts, I'm just stubborn and hate paying shop prices, not to mention the wait for the good shop in town. I'm a mechanic, but have no experience with outboard engines. The fact it runs great on the trailer and will lurch the whole boat and trailer forward in my make shift tank but has issues on the water is baffling. I was hoping it was something obvious to someone with the right experience. I have 2 local shops. The good one is booked out for the next 3 months, but maybe they can plug in real quick for me. The other leaves alot to be desired to say the least. I will try the local shops but I'm afraid I will end up taking it 4 hours away to the city to have them pull the codes. Thanks for the response, I appreciate it.

 

[flyingscott]

But that motor you are tied to the dealer. Just the nature of the beast. Or you can try to buy a scanner for it.