Not getting recommended WOT RPM's, Merc. 125

[aquanuts]

Hello to all,

New to the forum.

I recently purchased a 1996 Hewes Redfisher 18 with a 96 Mercury 125.
I am not getting the recommended WOT RPM of 5250.
WOT RPM is 4300 trimmed up and only 37 MPH on the GPS.
Turning 19 pitch Quicksilver S.S. prop. Appears to be slow out of the hole.

I removed and checked the carb's and found them very clean, main jets and bowls had no contamination at all. I still blew out all passages and jets.
Compression is good, 140 +/- 2 psi on all 4 cyl.

I noticed that the upper and lower motor mounts require replacement.

Also the warning module is bad, temp. and oil sensor tested good and the
warning horn turns on when you turn the key, I just ordered one.

Would the worn mounts or module cause the poor performance?
Any ideas on any other possible cause? Please help, thanks.

96 Hewes Redfisher 18, Merc. 125, 19P S.S., Lawrance, Lenco.

 

[cbucner]

Re: Not getting recommended WOT RPM's, Merc. 125

Try a 17 pitch and see if that gets your rpm's little higher.
You should see a 200 rpm increase and a better hole shot.
Try a 4 blade prop , I switched mine from a 3 to a 4 blade and I've seen a nice improvment.
Also your top end will drop about 2-4 mph.

 

[aquanuts]

Re: Not getting recommended WOT RPM's, Merc. 125

Thanks for the reply.

I'm pretty sure the 19P prop is not to much. The spare is a 21P and
I have read other exact boats running 19,s with no problem. Maybe
I'll try a 17P if I can't find anything else. Thanks again for the reply and
happy boating.

 

[aquanuts]

Re: Not getting WOT RPM's, Merc. 125 Pls HELP!

Re: Not getting WOT RPM's, Merc. 125 Pls HELP!

Hello Mates,

Not getting many replies, second time posting same issue.

I recently purchased a 1996 Hewes Redfisher 18 with a 96 Mercury 125.
I am not getting the recommended WOT RPM of 5250.
WOT RPM is 4300 trimmed up and only 37 MPH on the GPS.
Turning 19 pitch Quicksilver S.S. prop. Appears to be slow out of the hole.

I removed and checked the carb's and found them very clean, main jets and bowls had no contamination at all. I still blew out all passages and jets.
Compression is good, 140 +/- 2 psi on all 4 cyl.

I noticed that the upper and lower motor mounts require replacement.

Also the warning module is bad, temp. and oil sensor tested good and the
warning horn turns on when you turn the key, I just ordered one.

Would the worn mounts or module cause the poor performance?
Any ideas on any other possible cause? Please help, thanks.

 

[jsturkie]

Re: Not getting recommended WOT RPM's, Merc. 125

aqua, I have a Sea Ray 18' with a Merc 125. I have a 20p SS prop and get 5250 WOT. Cant tell you the speed I havent GPS yet but it seems plenty fast. I mostly run at 4000-4500 for a good ride. Check compression and spark. Sounds like you motor isnt giving all it can give.

 

[cell]

Re: Not getting recommended WOT RPM's, Merc. 125

Maybe theres some added weight to the boat.like wet flotation foam.Either way if your outboard is running like it should,and your rpm's are not where they should be at,it points to the prop...IMO

 

[fasassvalk]

Re: Not getting recommended WOT RPM's, Merc. 125

My lund 1800 pro-v loaded turns 5250 @ 42 mph with a stock 17P prop

 

[CharlieB]

Re: Not getting recommended WOT RPM's, Merc. 125

Possibilities are;

1 Heavy boat, any scale nearby that you could weight it?

2 Weak stator, use a DVA Meter to check stator voltage at max RPM

3 Too much prop, stop by your local prop shop, have a talk with him, see if he has a test prop to try before purchasing a new one.