Boat losing power

[Mariahshebah]

Hi All, I have a 1998 Mariah Shebah 180 with a 4.3 IO Mercruiser. I bought it this year and the boat is in immaculate condition. I bought it from a friend who I knew took care of it the last 7 years. Anyways, while I was on the water today, it was losing power as I increased the speed. Took forever to plain out. After sitting in the beach for awhile, it took off great but at cruising speed (30 mph) it started to lose power than almost immediately kick back to normal power. Did this a couple different times. Brand new spark plugs two years ago. I assume maybe something with the fuel filter? Forgive my ignorance but I assume the fuel filter is the same as the fuel filter water separator? I don’t know when/if that has been changed in awhile. Any thoughts on what it could be? Worst case, I will bring it in and probably end up paying a hefty amount but figured I would check here first for ideas. Thanks!

 

[Tassie 1]

You should try and find out from your friend when the filters etc etc were changed as well,
how old is the fuel etc?

 

[JASinIL2006]

Water separating fuel filter is one unit. Looks like an oil filter, sort of. One easy thing to check is to unscrew the filter (I hold a Ziploc baggie around to catch any spills as I spin it off) and the dump the contents into a clear glass jar. Let it sit for 10 minutes or so and if you see a layer of water on the bottom of the gas, you have found your problem. Or one of your problems...

 

[Mariahshebah]

I will give it a try in the morning, see if any water accumulates. Are there any other filters I need to be aware of? Or any other ideas if it’s not the water separator?? Thanks!

 

[achris]

1998 engine. The fuel filter is the water separator. It's under the front section of the starboard exhaust manifold...

 

[dubs283]

Are there any other filters I need to be aware of? Or any other ideas if it’s not the water separator??

depends, is this engine carb or efi?

spark plugs changed two years ago but how many hours ago? when was the last FULL tune-up?

 

[Mariahshebah]

Plugs were changed about 10-15 hours ago. My friend puts about 3 hours on a year, up here in northern MN.

 

[Mariahshebah]

I changed the filter, and appears to be no water. I also looked at the in-line filter going into the carburetor and it was perfect. Any other ideas? Bad gas maybe. I am going to bring it out, with new gas and run it today to see if the problem persists.

 

[Scott Danforth]

3 hours a year?

how old is the fuel?

I would be looking at dirt in the carb

 

[Mariahshebah]

Ya, the guy I bought it from a 80 years old who had it more so as a yard ordainment. He took very well care of it but just never used it. I’ve went through about 2 tanks now since buying it from him a couple weeks ago. Ran great up and until yesterday. I’m heading to the lake now with fresh gasoline and a newly installed water separator/fuel filter. We shall see

 

[Spidrmunky]

Does it get up to rpm okay? May want to make sure oil level isn’t too high. Oil overfill can cause underperformance and wet your plugs.