No Get-Up and Go on 77 merc 50

I have a 1977 Merc 50 4 cyl. mounted to a 14 ft. fiberglass skiff. It was recently worked on to change exhaust plates and carbs de-gummed and supposedly timed. I have a sting-ray fin attached to minumize porpoising, so here is a couple problems I encountered upon running this motor on this boat, oh yes and it has a 14P prop.<br />The take off is atrocious the motor seems to bog down upon full acceleration on take off and after a while it starts to rev up and gets up on plane and when I back down on the throttle a bit it loses its rpms and goes to almost idle speed but it is actually around half throttle on the stick,then bogs down again , until I slam it to full throttle then it starts its slow climb in rpms until I hit plane again. I did a compression check on the cyls and 1 2 and 4 have 120+ and # 3 has 100, which I was told was all in tolerance. So why is this motor bogging down on acceleration and taking so long to build the rpms up? The bow is extremely light on this boat, so could this be just a weight problem, that is the motor too heavy for the boat. I figured that the 50hp would make the boat jump out the water not set it down bog or cavitate whatever its doing. please help.<br /> Thanks

Re: No Get-Up and Go on 77 merc 50

Could this be a boat problem instead of motor problem, and or would a smaller motor be the ticket I need

Re: No Get-Up and Go on 77 merc 50

Has the motor ever performed better, or has it always been like this since you acquired it? Was it better or worse before you had it worked on, or was the poor performance why you had it worked on. We need a little more patient history here for an adequate diagnosis.

Re: No Get-Up and Go on 77 merc 50

The only time I ran the motor was in my yard so I can't help much on its history.<br />It seemed to run fine when I purchased it used from another person, but again it was only ran in the yard. The bottom carb was gummy and the mech who worked on it said there was green stuff coming out the carbs so he cleaned and reseated and adjusted. It has great fire or had, didnt check on that yet. He said he put everything in sync and he said he tried it out and seemed to be doing fine, but when I took it out hit the throttle the bow rose and the motor just sat down deep in the water and was straining to build up rpms. It took I would say 50 60 or so yards before it built up enough rpms to set the bow down. Also when at the launch I let it run while I got trailer jumped in hit the throttle and it killed 3 or 4 times so I used the warm up lever and it just sat and didnt build up no rpms with lever pushed all the way. When I approached trailer then the rpms built up for speed.<br /> Thats about all I can tell you. This was its maiden voyage for me and it was more like a nightmare.

Re: No Get-Up and Go on 77 merc 50

Well because you have no real history, there is a longer list of things to check. Possible things<br />1. Hard to tell from your description but might be running on 1 less cylinder than supposed to.<br />2. Mechanic did an inadequate job with the carbs and they still need work.<br />3. Boat has wrong propeller and engine is fine. (Too much prop, motor can't reach desing revs)<br />4. Mechanic didn't connect throttle cable correctly and you aren't getting full throttle.<br />5. Fuel, tank vent, anti-siphon valve (on tank), fuel line, fuel bulb, fuel connector, or fuel pump are interfering with fuel supply to carburetor.<br />6. The engine is trimmed up too high and is making it hard for the boat to get on a plane. Try trimming the engine down (so that the cavitation plate is level with the bottom of the boat).<br /><br />You can't tell about the performance from running it in the yard, the motor has to be submerged and under load.<br /><br />These are just a start. Keep us posted.

Re: No Get-Up and Go on 77 merc 50

also, is the cavitation plate even with the bottom<br />of the boat?<br />[edit] oops... didn't notice this was already mentioned. was thinkin u might have a reg. shaft<br />(20") motor on a short shaft transom or visa/versa

Re: No Get-Up and Go on 77 merc 50

1st the cavitation plate is even with keel of boat, the reason for the sting-ray is that the bow is extremly light, and all the weight is at the rear. I guesstimate with a friend including motor battery fueltank and fantail 500+ lbs. This is a 14FT skiff open bow, no real front deck but it has a hidey hole which I am filling up with sand for weight.<br />Also mechanic said it ran good when he took it out, but to me it seems like it is not advancing fast enough to keep up with the fuel therefore the bogging down on acceleration, and slow pick up to full throttle. I aint no mechanic but thats what it feels like to me.<br />Any thoughts I can pass on to mechanic when he gets here might help him fix the problem.