50 hp force too slow

[taggy]

I have a 1987 50 hp Force on a 1987 13.5 ' Bayliner Capri. So far I have had the carb rebuilt, all seals and gaskets in lower unit replaced, prop replaced ( don't know the size, sent the old prop to be reconditioned and the guy brought back two to choose from. He said one would get me up on plane faster and the other would give me better overall speed. I picked the one with better overall speed.) Compression was tested (fine), timing was set. I took the boat out for a test run after replacing the prop. My best guess was that we were getting somewhere around 20 mph (great). That was the only time that we got that speed, ever since then it's been 11 and now I can't get past 8 mph. I replaced the cables today hoping that would help, but no luck. I read someone elses post about a missing exhaust snout, but mine is fine. I don't know what to do now?

 

[Barnacle_Bill]

Re: 50 hp force too slow

Did you check for a strong spark at all plugs?

 

[taggy]

Re: 50 hp force too slow

Both plugs are new, but I did not check them. I had a marine mechanic doing all the work after I replaced them, so I am trusting in his knowlege. I've had him on the boat for test runs. He thinks that maybe it's the wrong prop, but my question is why did I get the speed one time?

 

[hoofbite]

Re: 50 hp force too slow

It's not the prop if once got speed and are not now unless you really bashed it on something. If you had a marine mechanic work on it and your not satisfied? Then the best thing to do would be to take it back to him and ask him you want what you paid for!! In my neck of the woods there are too many 18-20 year olds that think they know what they are doing as far as these older motors go.

 

[emoney]

Re: 50 hp force too slow

I just saw your thread after I posted my own. I have a 1983 Chrysler
50 and it's doing the same thing. I'm like you, and waiting on replies,
however as I'm sitting here I'm thinking it could be a fuel issue. I didn't
check my fuel pump diaphram, just the screen. From what I've read,
a bad diaphram would starve the motor of fuel, especially noticeable
as you increase the throttle. As a matter of fact, I had a little "cut out"
in mine, not bad, but enough to notice as I hit WOT.

We've got the same issue, as my boat was only going 9.5knots which
is less than 11mph. If I get the solution to mine before you do, I'll share
what I found, if that helps. Hopefully, we'll both get 'em resolved.
Good luck!

 

[taggy]

Re: 50 hp force too slow

I forgot to mention that the fuel pump, water pump and thermostat were also replaced. There is one thing that I thought of, but don't know if it is enough to cause this problem. I keep this boat in the water in Florida. Barnacles start to build up pretty quickly. When I had the boat out of the water, I cleaned the bottom. The first trip out was with a clean bottom. The next trip was a week later with buildup on the bottom. Could that do it? It does seem to keep getting slower each time I take it out. The bottom is kind of gritty right now. If that is it, should I paint the bottom?

 

[emoney]

Re: 50 hp force too slow

This one I can probably answer. The buildup on the bottom can affect
performance, but not by reducing the speed by 50%. If it was a matter of
"Top speed was 28mph and now it's 25mph" then that could be the culprit.
I live in Florida, as well, and my sailboat stays in the water. I've found
when the bottom is particularily dirty I lose a 1/2knot to maybe 3/4knot.
Of course, a sailboat isn't a 'planing hull' so top speed is hull speed which
is 5.2 knots (roughly 6+mph).

If the boat's lived in the water quite a bit, then you would be best served
to pull it out and do a very thorough going over it. Salt water is very
corrosive, especially to the many seals and gaskets in an outboard (most
definitely and older one). I watch a lot of people 'flush' their engines for
2-3minutes and assume all is well, when a lot of times that's not enough.
Doesn't help for the problem at hand, but advice anyway.