50hp Merc 1984 4 cyl 2 stroke

[tmugg]

Gentlemen, about a month ago I bought a 15-1/2' Baretta fiberglass bow rider with a 50HP merc. Motor starts and runs well. She takes off fine and slowly accelerates to about 15 MPH but then just will not top out. She sits at about 2800 RPM at max throttle and just about 20 MPH. The tri hull boat weighs 800LBS motor weighs 168 LBS and I have two riders at 200 LBS each. In neutral the motor will rev nicely well up past 4500. I checked the prop chart and the prop is right in the middle for the weight and length of the boat ( 10-1/4", 14 pitch). I'm at a loss for what to check next. The boat sat for 5 years so I changed the water pump and gear lube. Its really a clean motor/only fresh water. Lower unit seems to spin freely. My next thought is to check the ignition system to see if its firing on all cyl. Any ideas?

Thanks

TJ

 

[anzomcik]

Re: 50hp Merc 1984 4 cyl 2 stroke

Well you first need to make sure the motor is running correctly.

Do you have power trim? if so have you played with it to try to plane out the boat?

Have you mess around with trim settings if it is a manual trim?

I have a friend who has a 18 foot aluminum with a 50 hp merc its older than yours. I bet the boats might be around the same weight and he has either a 10 or 12 pitch i can not remember, but either way it is less than yours. His motor pushes his boat very nice maybe mid 20s.

Get your ducks in a row, try a few things. Get hard numbers gps speed and wot rpm then we can go from there

 

[tmugg]

Re: 50hp Merc 1984 4 cyl 2 stroke

No power trim. She is set out one trim hole from level. Prop chart tells me I can go to a 15 pitch but not with a big increase in speed.

 

[steelespike]

Re: 50hp Merc 1984 4 cyl 2 stroke

Reving in neutral means nothing and can lead to a runaway(uncontrolable overreving)
Check that all cylinders are firing.You wouldn't be the first to not realize an outboard was missing a cylinder.Check that the carbs are syncronized and opening all the way.Tickle the choke see if it responds.Be sure the stator is advancing as it should.