86 Force 125 - is my speed about right for this motor?

[mbhoag]

Finally got a chance to take my 86 Bayliner Bass Boat (18') out on water that I could open it up to WOT.

At WOT I was running about 4500 RPM, 35 mph per boat speedo, (39 mph per GPS on my droid). I have a stainless prop (no idea how to determine the pitch of it)

It was an extremely windy day and very choppy with 1 -2 foot chop. I know the conditions will slow me down some, but does this RPM and speed seem about right for this motor on an 18' bass boat?

I am happy with how it ran, but have no idea if this is good, bad or average speed.

Thanks for your help and input!

 

[bentle]

Re: 86 Force 125 - is my speed about right for this motor?

Rpms should be 5000-5500 at wot. Stainless steel prop may be to much pitch for your motor. For example. I have a 18' Maxum with a 120 force. When I purchased the boat it came without a 17 pitch aluminum prob and an 18 pitch stainless steel prop. Well both are just to much pitch for my motor. I have never tried the stainless prop and the 17 was crappy coming out of the hole. Rpms were about what you are getting on yours. Well I purchased a 15 pitch aluminum and now hole shot is where it should be and rpms are 5400-5500. Try a 15 pitch aluminum and im sure you will be happy.

 

[fucawi]

Re: 86 Force 125 - is my speed about right for this motor?

well my last 115 yamaha was running a 20 pitch and your 125 is the same HP ..15 seems very low to me ..pitch should be on the prop stamped on the hub between the blades or on the hub base .....if its just a number try the Michigan prop site for a figure .. The book shows 15 -19 p with 19 p for the smaller boats 18-20 ft

 

[azlakes]

Re: 86 Force 125 - is my speed about right for this motor?

Try again on calm waters with no wind and you should be at 40+mph, sounds like you are in the range for the conditions you were in...

 

[mbhoag]

Re: 86 Force 125 - is my speed about right for this motor?

Had a chance to get the boat out on a calm clear day yesterday and it ran pretty good, but seemed to sputter a little. Top speed about 40mph (per gps).

After my first run of the lake I shut her down, gently reseated the carb screws and turned each out 1 1/4 turns. This time down the lake speed was at 43 mph and about 4600 rpm. I may need to open up carb screws another 1/4 turn or so, but seems to be doing pretty good as it is.

Should I be concerned that I am not getting over 5000 rpms out of her?

 

[Frank Acampora]

Re: 86 Force 125 - is my speed about right for this motor?

The rated RPM operating range is 4500-5500 at WOT. These engines like to run at the top end of the range, but at 43 MPH, you are doing OK in speed and at 4600 you are within the published RPM range.

You MAY want to experiment with different pitch props, but if you are happy with current performance, stay as you are. No damage should be done to the engine by running at the current top RPM.

 

[fucawi]

Re: 86 Force 125 - is my speed about right for this motor?

If you have any sense you will not be running WOT all the time ..maybe 3/4 throttle as every motor has a sweet spot for speed and fuel consumption....if you drop the pitch it will get very noisy ..17p is about right for a 70 hp so I carnt see 15 p being any good on a 125

 

[jerryjerry05]

Re: 86 Force 125 - is my speed about right for this motor?

The air screws are for the air mixture. They aren't effective much past mid throttle.
They should be set at an idle,in gear and motor warm.750-800 rpm's
Start at 1 and 1/16th out.
As far as opening them up too much(air screw) you can burn a hole in a piston that way!!!
AS far as pitch it depends on load and rpm's.

A 125 with a 15p is suited for a pontoon boat or a bigger boat.
My motors run great about 3800- 4200.Both with 17p.
My boat is 21ft and 8ft wide.And fairly heavy.Twin 85's
I put 19's on it once and got faster about 5mph.
And it also consumed about 20-25% more fuel with the 19s.

Remove the prop,it should have a # stamped in it somewhere.

 

[mbhoag]

Re: 86 Force 125 - is my speed about right for this motor?

Thanks for all the help. On the air-screws everything I have found says 1 1/4 to 1 1/2 turn out, but I will certainly play with 1 1/8 next time I am on the water.

As for the prop, I am guessing I have a 15 Pitch, but not sure how to make sense of the info stamped on my prop. Photos attached of the two stampings that are on it (not the easiest to read, so I rubbed with black marker then wiped off excess..now a tad more readable in pics.