Force 50 Mystery

[Docdoc]

This is pretty aggravating. I bought a 1988 force 50 hp on ebay late last summer. The dealer I bought it from claimed compression of 150 in both cylinders. When I got it, the carb was in poor shape, so I switched it with one I had off a Force of same year and HP. Motor started and ran fine, but didn't seem to have as much speed as the prvious force 50 I had. I didn't mess with it much because it was late in the season. <br /><br />I decided to tune up for spring and did what I thought was needed (decarb, carburetor kit, new water pump). Anyway, after all that, I can't get the boat to get up and plane. I tried different prop (off old motor), and messed with the trim, but still can't get it to plane. Almost seems like it's not turning enough RPMs. Fuel system is okay and I'm getting plenty of exhaust out the lower leg.<br /><br />The boat is a 16 ft fiberglass Bay skiff with small tunnel in the back. The 50 HP Force I had on it before did just fine and pushed the boat about 20+ mph. I'm stumped. Help!!

 

[eurolarva]

Re: Force 50 Mystery

Check you spark plug tips and see if they have the same burn pattern on them. Both should have a slightly grimy look to them. Buy a compression tester and test the compression. (Auto parts stores and Sears sells them for about 30 bucks). Rebuild the fuel pump (about 10 bucks) and replace all the fuel lines and the primer bulb. I would do the compression test first. The plug tips may show lack of compression in one cylinder or lack of spark.

 

[Docdoc]

Re: Force 50 Mystery

Fuel lines were replaced last year when I got the motor. Bottom plug was pretty dirty before I decarbed. Now both plugs look about the same after an hour out on the water ( a little oily with some residue).<br />I have noticed some black oily residue on the flange around the power head at the stern of the engine. If I wipe it up, there is more after the motor has run a bit. Leaky head gasket?<br /><br />I checked torque on the head bolts and one bottom bolt was under torqued by about 60 inch pounds. Guess I'll invest in a compression gauge and let you know what I find out.<br />Thanks,<br />Jerry

 

[12Footer]

Re: Force 50 Mystery

If it's a tunneled hull at the transom, check that everything below the cav plate has clean water, no bubbles. Check the hull for barnicles or other bubble makers that may interfere with the prop getting a clean bite.<br />The prop hubs on these motors are so weak, I would also put a line of paint accross the hub to one blade, just to confirm no slippage.<br /><br />Check that the throttle plate in the carb is opening fully in the WOT throttle position.

 

[Docdoc]

Re: Force 50 Mystery

Okay, just did a compression check according to instructions in Clymer manual. Compression in top cylinder is 140, bottom cylinder is 139. That should be plenty good enough for planing the boat. Throttle plate in wot postion is perfectly horizontal. Prop hub problems aside, could timing be a factor? Acceleration is smooth. Gonna try some brand new plugs and see what that does out on the lake tomorrow.

 

[bioman]

Re: Force 50 Mystery

Hey Docdoc/Eurolarva/12 Footer... my favorite outboard repair dudes... Let me float an idea out here.<br /><br />My Force 50, ('87)has the same icky leak near the back of the cowling...I think it was Eurolarva that suggested exhaust manifold leak.. which I haven't cured yet. <br /><br />If the manifold leak is throwing half-burned air into the cowling and being sucked up by the carburetor, the engine is starving for 02 (my theory). Simple test is to run it WOT without the cowling on. <br /><br />P.S. If you find the cause/cure for the exhaust leak, I'd appreciate your sharing it. (short of pulling it all apart...<br /><br />bioman

 

[Docdoc]

Re: Force 50 Mystery

Bioman:<br />Have you run your motor wot without the cowling on? If so, did you get satisfactory rpms than with the cowling on? Sounds like a reasonable explanation to me. I was about chalk it up to timing and check that, but I can't figure out out to hook up my conventional automotive timing light up where it will work to check wot timing.

 

[eurolarva]

Re: Force 50 Mystery

Bioman. What motor do you have. If it is an early model chrysler they have a check valve that drains unburned gasoline oil mix and dumps them into the motor leg and out into the lake. The newer model chryslers and I believe force uses a puddle valve system that recirulates unburned fuel back into the motor to be reburned. When the motor idles alot gas condenses and then settles and is reciculated through this puddle valve system. <br /><br />If your motor has a puddle valve system take it apart and clean it out. Be careful running that outboard at WOT with the cowling off. First of all that powerhead is spinning real fast. Also the motor design is made to have the cowling on. Running with it off may induce too much air into the mix. Troubleshoot with it off to find where the sludge is coming from. It is not recommended running it for long periods of time with the cowling off.

 

[Docdoc]

Re: Force 50 Mystery

Eurolarva:<br />Isn't the puddle system cover on the same side as the tower shaft? Also, with a small exhaust leak like that, would it cause such a drastic reduction in rpm at wot? It seems to be turing at only 1/2 speed.

 

[bioman]

Re: Force 50 Mystery

Docdoc-my moto can whine way up w/out the cowling... stumbles like crazy with it on (not to mention I can't hand-control the throttle with the cowling on...which makes me think exhaust air is messing up the mixture.<br /><br />Eurolarva-motor has a "fuel recirculation" valve which I think is same as puddle valve. Haven't taken it apart, but the hose is hard so I do need to replace it. The sludge is port side aft (near the exhaust). same place Docdoc reported. Is there a part of the puddle valve system near there? <br />And I'm really sorry you mentioned that powerhead spinning 'cause it scares the heckoutame to run it open... but I figgered they just don't fly apart or no one would ever do it... now I'm scared...<br />Bioman

 

[Jcrain]

Re: Force 50 Mystery

Bio man,<br />Trust me...if that force decide to come apart, the cowling won't slow anything down, just make a heck of a racket as the flying peices make new vent holes in it.

 

[bioman]

Re: Force 50 Mystery

Thanks Crain....thanks a lot. Is that voice of experience?<br /><br />P.S. Can we get back to scaring Docdoc now?<br /><br />;-)

 

[Docdoc]

Re: Force 50 Mystery

Bioman:<br />Are you running your motor in forward gear, in the water, at wot, without the cowling? If so, why would you want to hand control the throttle?<br />Just curious. mine will wind up too with no load on it, but that isn't the condition I run it in.

 

[Docdoc]

Re: Force 50 Mystery

Ok, I took the fuel recirculation (puddle) valve apart and cleaned it. It seemed to be okay. I haven't removed and inspected the check valve on the other side of the motor. Can anyone tell me how to hook up my timing light to check wot timing? I know I need both plugs pulled out and the light hooked up to #1 spark plug lead, but how do you get it to spark without being hooked up to the plug? Is this one of those "special tool" situations, or can I rig something that will work?

 

[eurolarva]

Re: Force 50 Mystery

The puddle valves are to improve idling. I doubt it would have any effect on the mid range to WOT. Sorry I cant help you with the timing. I have a chrysler and looked at the parts for your motor and it is a different beast. If the check valves are part of the recirculation system it might not hurt to check them if it isnt to hard to remove and check. <br /><br />You should still have that prop checked for a spun hub. Next time you have it out on the lake use a permanant marker as 12 footer recommended. I remember reading about these 50 HP Force motors being real hard on props causing them to slip. I hope someone else can help you with the timing issue.

 

[Docdoc]

Re: Force 50 Mystery

I appreciate all your help, eurolarva. I did check the prop hub as suggested. I scribed a mark on the hub and base of the prop, ran it under load at the lake and there was absolutely no movement of the marks. I'm gonna jump on to timing as the culprit now. If that doesn't pan out, then I will (gulp) try to fix the exhaust leak you suggested.

 

[Docdoc]

Re: Force 50 Mystery

I think I've been looking at the wrong problem all along. I tried to hook up a timing light and couldn't get it to flash on the number one spark plug. In the process I noticed that #2 plug was sparking but #1 wasn't. I think there is an ignition problem that has been causing the lack of power all along. Is it possible for a 2 cylinder to start quickly and run smoothly on only one cylinder? Is there a simple answer to this? Eurolarva, where are you, buddy?

 

[eurolarva]

Re: Force 50 Mystery

I hear about 2 stroke motors running on one cylinder all the time here in iboats. The answer to your question is yes. Mercury had a bad batch of coils that was causing problems when the motor heated up the coil would stop working. As I mentioned before my experience with the electronics on an outboard is very limited. I dont know the troubleshooting procedures to fix this however it is outlined in the syloc manual and the clymor. I believe you can test the coils with and ohm meter and the rest you will need a DVA adaptor to work with a digital volt meter. You might want to do a search on force ignition testing. Good luck

 

[Docdoc]

Re: Force 50 Mystery

Fortunately, I may not have to be too samrt about this. I have a spare CD module/coil set I took off my other Force 50 motor. I think I will slap it on tomorrow and see if #1 fires.

 

[Irish Rob]

Re: Force 50 Mystery

Am having the same problem with exhaust leak in cowling and I'm losing speed with it on. I have a 98' 50hp force/mercury. Can someone run me through the steps to fix. Any help appreciated. Thanks.