Force 50

[Force3555]

Motor starts right up idles good but sputters on and off when increasing power.

 

[Nordin]

First of all start with checking for spark at both plugs and checking the compression.
If those two things are in order go on with clean the carb.
The compression should be about 140-150 PSI but can be lower down to about 115-120 PSI.
Important that both cylinders are pretty equal in value, maximum about 10% in differens.

 

[Force3555]

Thanks for quick responce.
Compression is very close to 130 both cylinders.
Ran and found feathering choke stopped the sputtering and reduced rpm's slightly.

 

[roscoe]

Likely running a little lean.
Clean carb and reset idle mixture screw.
Also check carb to intake gasket. No air leaks aloud.

 

[Force3555]

Did everything recomended. In neutral revs up.Also cleaned points and carb as well as a new carb gasket. Put in water motor starts great idles good.
When in water in gear increasing throttle rpms go up to about a quarter then rpms stay there even if pushed all the way. Carb adjustments make no difference.

 

[chris.olson]

A couple things come to mind. Have you verified the linkage sync and ignition timing? I demonstrate how to set it here. Making sure the linkages are sync'd is very important because if somebody has messed with it and got it wrong by setting the link from the tower shaft to the throttle cam too long, you can actually reach full throttle at partial advance. Then moving the control lever further moves the throttle plate over-center and closes the throttle as the timing continues to advance. Consequently it won't have any power.

https://youtu.be/UD-wW5WOJpk

If everything is correct and you're 100% certain you're not running lean (very dangerous for engine health) then is the boat over-propped? It is on a pontoon or something where it can't reach minimum 4,500 rpm? Or is this in a test tank maybe where the engine is being lugged similar to trying to get on plane?

 

[Force3555]

TIA for all the help. Did all the things recomended and the boat is running exellent. Have run it about twenty miles mostly full throttle and top speed varied a little depending if I was alone was about 22 and with another person about 20 mph.
Is this a reasonable speed for an old 15 foot tri hulll estimated weight with two people 1000 to 1200?

 

[chris.olson]

Yes, that's right in the ballpark for a 10 x 11 prop with no special rigging. We have the same engine on an Alumacraft Pro 17 with a CMC power tilt and trim that moves the engine back and allows raising it so the anti-ventilation plate is above the keel and ventilates the prop on plane. So I have it rigged with a 10 1/'2 x 13 prop and it goes 29 mph GPS at WOT and 5,700 rpm. Pulling it back to 4,200 rpm gives 22 mph on that boat.



You would have to have a tachometer installed to know what you are turning at WOT and make a decision on engine mounting height and prop to get any better than you are getting.

 

[Force3555]

Thanks will try the other two angle positions and see how it works.

 

[chris.olson]

With fixed trim the best you can do is trim it so the anti-ventilation plate and prop shaft are parallel with the water flow. This will hurt the hole shot slightly and result in bow high getting on plane. But will provide the best performance on plane.

The only way to have the best of both worlds - quick hole shot and best plane performance is to add on a power trim system.

You can try the different holes on the pin. But there's only one that's basically going to provide good all-around performance. And that's going to depend on boat loading (front or rear weight) to a great extent, and the angle of your transom. Look behind the boat when it's on plane. Is the anti-ventilation plate on top of the water? Or are you dragging it thru the water because the engine is mounted too low on the transom?

There's a lot of variables in rigging. But reality is that you are right at the typical speed for a 50 on a boat of that weight unless you do some serious work on rigging for performance. And that will include a CMC power tilt and trim system. Which is about a $900 item here on iBoats, for the 130hp capacity unit.

 

[Force3555]

Thanks

 

[chris.olson]

It will be interesting to see how it works out for you. For most people that can get the boat on plane, throttle back and cruise on plane at reduced power, the fixed trim is "good enough". OTOH, like our boat, trimmed all the way down, will come on plane pretty fast and top out at about 4,200 rpm even at WOT. Trimming it up and getting it on the pad ventilates the prop and gets it up to peak horsepower and it gains 7 mph, just in trim.

IMO, the CMC power tilt and trim is worth the money if you're on a big lake and do a lot of running on plane. It not only adds the trim and tilt, it allows getting more of the lower unit out of the water further back from the stern where that water leaves the keel and rises to fill the void. If we trim it sensible we haven't had any problem with water pickup for the water pump. But it definitely adds performance that a fixed-trim motor won't achieve.