1980 mercury 115hp hard start and trim??

[Joeshow]

Hi people!
This thing flys on my 1975 Starcraft 16' American!! The ol 115 purrs like a kitten once started n warm and takes the boat to 70kmh (43mph?) !!!! Not sure on the rpms (tach rests at 3000 with engine off, at wot it goes to 5500)

The down side is, she's real hard to start! It takes about ten minutes of cranking over then 5 minutes of warming up before you can go ( I might be exaggerating a little) and the trim motor is replaced with some convertible car top motor. The trim slowly drops the merc ( doesn't hold the engine up ) would this be from poor cylinder seals in the trim rams?

I greatly appreciate any help!!

Thanks,
Joe

 

[Georgesalmon]

Re: 1980 mercury 115hp hard start and trim??

What year motor? 1975? They can be hard starting when cold but not that hard. Is your choke working correctly? Do you hear a click when you push in the key? Does it have a manual choke rod at the top of the cowling you could try? Is the motor new enough to have an enrichment valve? WOT of 5500 is right at the top. Might be poor valves or no valves in the conv top pump.

 

[Chris1956]

Re: 1980 mercury 115hp hard start and trim??

Joe, To start it, prime the motor until the blub is hard. Cold start lever all the way up. Hold choke button and crank her until she starts.

You just replaced the trim motor with the convertible top motor, or did you replace whole PTT motor/reservior? The motor will settle if the teflon piston seals on the trim cylinder pistons are bad, or the control valve (in the PTT motor/reservoir) is bad. What do you have?

 

[Joeshow]

Re: 1980 mercury 115hp hard start and trim??

Hey, it's a 1980, it seems everything is there. I'm waiting to use someone's pc to download a manual for it, my iPhone won't let me.

I stumbled onto Chris1956's way of starting yesterday morning!! Trial n error! Lol

As for the trim motor, the convert able top motor eliminates all the factory pump and resivor, the Hydralic lines plug right into the convertible pump! The previous owner did this because he was told by the marine mechanics that it would cost $1500 to replace. He gave me the original pump/resivor. I have it working out of the boat without oil in it, it's a little loud tho.
I'm scared to get it all hooked up in the boat and the pump still not pump! Plus the convertible pump says ATF on it and the merc pump says 10W30 or 40.

I'm not too sure what to do. It would be real nice to have the engine stay up cause there is a lot of shallow water and boulders in my parts of the river (Trent Severn narrows)

Thank you both for your feedback!! I can't wait to get a manual!!

 

[Chris1956]

Re: 1980 mercury 115hp hard start and trim??

ATF is OK to use in the PTT system. That is the least of your problems. The original PTT pump had a control valve that held pressure to hold the trim against full motor power. In additon the control valve would allow the motor to tilt up if you hit something at speed. I have no idea if your new pump has this feature. If not, and you will know it soon, the motor will likely trim down under some amount of power. Aftermarket PTT motors are avail. If you still have the pump base and control valye, you might go that way. I would think you can get an aftermarket PTT pump for ~$200

 

[Joeshow]

Re: 1980 mercury 115hp hard start and trim??

The PPT pump and control valve, I have it working I think (out of the boat)... Would it be normal for it to make some noise without fluid in it? How hard is it to bleed the system? Or do the bubbles just find their way back to the resivor with use?

The system installed now, there is no valve to keep the engine tilted, she slowly falls... Under idle, I need to keep bringing it back up. He did use the original hoses for the PPT system

I'm scared that I'll get the PPT/valve system in and it not work. That would be a lot of messy work for nothing lol

 

[Chris1956]

Re: 1980 mercury 115hp hard start and trim??

Fill the OEM trim pump and run it to make sure it pumps. If it does, reinstall it, as I doub't the system you have will work well. The pump is self-bleeding, but the trim cylinders are not.

 

[Joeshow]

Re: 1980 mercury 115hp hard start and trim??

Alright, you've convinced me! Lol I tried it, it pumps fluid!! Now to drain it and put ATF fluid in cause the motor in the boat now says to use ATF, so I figure they would have used ATF lol

 

[Joeshow]

Re: 1980 mercury 115hp hard start and trim??

Well it's not good. Lol I checked the fluid used in the boat and it is motor oil, so I filled the TTP with 10W30 and installed it. It worked for two ups and downs noisily then would only go down... Tried playing with the knob on the pump but no change. So I guess I'm swapping it back to the convertible motor for now till I get the pump fitting housing. Was worth the try!!

 

[Joeshow]

Re: 1980 mercury 115hp hard start and trim??

Well I've been searching for where this brown white wire goes, it's near the trim motor and battery area. It has a connecter that seems it should be attached to a small terminal on a solenoid. But which one?? I tried to down load my manual last night but I have too poor of signal on my air card, kept loosing service around 30mb and the file is 210mb, not happy!!!!

I connected the yellow red wire to positive on the solenoid at the trim pump, seemed to help starting a lot!! Anyone know where the brown white wire goes?

Thanks again!! Greatly appreciate the help on this site!!!

Oh and it only took me 25 minutes to disconnect the PPT and reinstall the seabring convertible top motor!!

 

[Chris1956]

Re: 1980 mercury 115hp hard start and trim??

Joe, What kind of controls do you have? Is the brown wire on the boat harness? Normally the brown wire is either a tach signal wire (old wiring colors) or trim sender wire (new wiring colors). If it is a tan wire, it may be for overheat alarm. Your '80 motor does not have a trim gauge sender or an overheat sensor. You will have a brown tach sender wire if you have the old wire colors. The colors changed about when your motor was made....

 

[Joeshow]

Re: 1980 mercury 115hp hard start and trim??

Well Chris, my controls have a trim toggle up n down then a trailer to raise the motor right up. The idle rpm button is where the lever pivots. The choke is engaged with pushing the ignition key in. My tach wires come from the bow side of the controls.

I believe it has a trim sensor because the toggle trim only works within an operating range.

Think I'll try downloading the manual again lol

 

[Chris1956]

Re: 1980 mercury 115hp hard start and trim??

Joe, The trim limit switch (on the starboard PTT bracket) controls when trim stops and tilt starts. Of course on your system, the same components are used for both. When I said trim sender, I meant the sender for a trim gauge.

BTW-Those trim limit switches break after a while. I always just bypassed them.

 

[Joeshow]

Re: 1980 mercury 115hp hard start and trim??

Ah, ok thanks! Good to know!

I finally have the manual

Would you happen to know how much work it is to make this 115 to give 140? They are very similar!! All I've seen different is carb jetting so far. Timing, bore and stroke are all the same... Wiring is the same for 1980 and 1981... Exhaust might be different? I'll do some research here soon lol

 

[Chris1956]

Re: 1980 mercury 115hp hard start and trim??

I think you will find port differences on the blocks. Check part numbers on the block and transfer port covers. I think they are different. The 140s used power ported pistons, which work with an elongated transfer port. I did not think the 115HP of that year used them.

 

[Joeshow]

Re: 1980 mercury 115hp hard start and trim??

Yeah there is differences..

Well about my trim pump, I got into the gears and valves. Noticed the drive shaft was not seated in the gear, so I pressed it in. Noticed the valve on the outer edge of the two is set just below flush. I'm thinking this is the cause of my system not working, after the initial 2 cycles of up and down? 2 times now that I have installed this, it worked for 2 cycles then nothing.

Now the boat is 15 miles away n I don't drive.