1995 Merc 115 slowly loosing power

[richw46]

It's firing on all 4 cylinders, I just didn't understand the 2+2 idea, if the timing light is blinking for each cylinder at idle. racerone says the bottom 2 don't get fuel so that makes sense, it would still be making spark. It idles OK.

I took it down to the lake yesterday. It started on the first crank and idled OK. I took a run down the lake; 47 on the speedo, 45.8 on the GPS. I fished further down the lake another couple of miles, then made a full run back to the dock; 48 on the speedo and 46.9 on the GPS.

From idle through no wake to half throttle up to WOT, there is no missing. Sometimes, when it first starts, even warmed up, it may "sneeze" (for lack of a better term), then it starts. Coming from a long run up to the dock, then just a slow idle up to the dock, then reversing, it can die, starts up again, however. (The only time it's been hard starting is when I put dielectric grease on the sparkplug connection. I wiped that off and there have been no starting problems since then. Now dielectric goes only on the boot and ceramic area.)

Since I'm hitting 48, mostly flat water on a straight run, I'm not going to worry about it anymore. I could have the carbs rebuilt for $600 to $900 but for what? 5 MPH? I think I'll just be happy and spend more time fishing, less time trying to squeeze another 5 MPH out of a well running engine.

Thanks everyone for your help. I've learned about 2+2 and how to do a compression test. I may yet check the timing but unless that needed to be adjusted when the voltage regulator was replaced, it should still be at factory.

 

[racerone]

???_--Look at the carburetors.----You will no doubt see that the upper 2 have adjustable low speed mixture screws.-- The bottom 2 do not have that feature !!

 

[ondarvr]

It's been a little tough getting this through to you

If the carbs are dirty or need adjusting it can destroy the motor by continuing to run it that way. I'm not saying dirty carbs "are" the problem, but you need find the reason for the loss of speed or you may be buying a new motor.

 

[richw46]

???_--Look at the carburetors.----You will no doubt see that the upper 2 have adjustable low speed mixture screws.-- The bottom 2 do not have that feature !!

I understand, thank you

 

[richw46]

It's been a little tough getting this through to you

If the carbs are dirty or need adjusting it can destroy the motor by continuing to run it that way. I'm not saying dirty carbs "are" the problem, but you need find the reason for the loss of speed or you may be buying a new motor.

Thanks, ondarvr, I understand, but I'm at the mercy of the Mercury mechanics. The last one didn't find anything wrong, cost me $100+ for that information. If I take it to another Mercury mechanic, without something definite to tell them (other than I lost 5 mph and Sea Foam isn't fixing it) I'm sure they'll be happy to charge me $100 an hour or more to look and see what they can find and start throwing parts at it. Three Mercury mechanics that I've had look at my motor in the past caused more harm than anything, leaving off screws, nuts and causing other problems. I could ask them to rebuild all 4 carbs, but if that isn't the problem I'm out close to a grand.

I am considering rebuilding them myself. I have put kits in carbs on my cars (2 and 4 barrel) in the past. The kits aren't terribly expensive. I may do this over the winter as a project. I have the recommendation for another Mercury mechanic, but the guy who recommended the mechanic said it may still not solve my problem.

My boat trailer had problems with the brakes seizing on me. I took it to 4 different dealerships in 4 different cities, starting with the dealer who sold me the boat. He accidentally cut the brake line and the reservoir was empty when I got home (his 4th attempt to fix). One put on the wrong part, one bled the brakes but it still froze up on the next trip, one replaced the rotor and calipers but in 2 years it started freezing again.

My boat is kept in a heated garage. I pull regular maintenance on it, what the owner's manual calls for. I ended up calling Ranger, getting the part information, buying replacement parts, tools and putting it all together myself. 4 years and no frozen brakes. I don't understand why a trained mechanic can't do something I can, with no training, just shade tree experience. I guess it's a bad case of NMB/IDC (not my boat / I don't care).

I'll think about either taking it to the recommended mechanic or rebuilding them myself (Timing check first, that's the only other thing I can think of besides the carbs.) At this point I'm having a really hard time trusting mechanics.

Thanks for your help and concern.

 

[ondarvr]

It's very easy to work on the carbs, I understand why dealers charge so much for rebuilding them, but it's not hard to do.

 

[richw46]

Well, so now I'm 2+ more years down the road with this motor. I REALLY appreciate all the feedback.

In October I removed and cleaned all 4 carbs per a YouTube video I found. The carbs were pretty clean, not what I would consider dirty at all. Sprayed and soaked the parts in carburetor cleaner, replaced all the gaskets with Mercury kits. and put them back on the motor, torqued the nuts to 100 in. lbs. I replaced the 2-stroke oil reservoir to oil pump line and bled it before starting the motor. I replaced the water separator canister and fuel line/squeeze bulb 2018. I stopped putting in Sea Foam after the last can this fall. I stopped the Quicksilver Quickleen in 2017. I've tried 91 octane, ethanol-free gas; no difference in performance.

Running at full throttle I'm still at 47 mph with just me in the boat and about 1/2 tank so the problem hasn't worsened. RPMs are at 5200, right where they're supposed to be according to prop docs I found. I switched to a new 4-blade prop and RPMs dropped to about 4600, lost 1-2 MPH top end but gained a better hole shot and faster planing. I've gone back to the 3-blade.

Since the motor is running well I think I'm just going to accept that it's not going to get up to 50 anymore. I've thought about a new boat and when the wife quits laughing she says I've got another think coming. As long as it's starting and running well I should be happy and focus on my fishing.

Thanks again to everyone for your expertise and patience.

 

[flyingscott]

Have you checked the stator? Those motors are known for the high speed windings going bad in the stator. That will cause a speed and rpm drop off.

 

[Texasmark]

Have you checked the stator? Those motors are known for the high speed windings going bad in the stator. That will cause a speed and rpm drop off.

Say What?????

--------------

Rich W 46, I bought that engine last June on a 17.5' Crestliner Fish Hawk. That hull is aluminum and has reverse chines with a 12 degree dead rise at the transom. Trimmed out, the spray exits at the corners of the transom.....meaning there isn't much hull in the water and the reverse chines give it good lift. In getting the rig setup the way I want it, I found that to get 50 is doable with a 20P Mercury Laser SS prop. at 5250 rpm....barely on a 50 degree day. That tells me that I am getting all I am going to get out of the rig and that's fine as I plan on running cruising speeds, 20-25 most of the time....but i had to get it setup first.

Temperature and humidity determine the density of the air which affects the size of the bang when the cylinder lights off. I read where in worst case conditions, temperature extremes could change your performance by as much as 25%. Soooooo if there is any truth in that number, not knowing what "at temperature extremes" means, your not getting 50 could have nothing to do with your engine's current condition; just that you had a data point one day and you haven't been able to duplicate the conditions and get it again..

 

[flyingscott]

Say What?????

--------------

Rich W 46, I bought that engine last June on a 17.5' Crestliner Fish Hawk. That hull is aluminum and has reverse chines with a 12 degree dead rise at the transom. Trimmed out, the spray exits at the corners of the transom.....meaning there isn't much hull in the water and the reverse chines give it good lift. In getting the rig setup the way I want it, I found that to get 50 is doable with a 20P Mercury Laser SS prop. at 5250 rpm....barely on a 50 degree day. That tells me that I am getting all I am going to get out of the rig and that's fine as I plan on running cruising speeds, 20-25 most of the time....but i had to get it setup first.

Temperature and humidity determine the density of the air which affects the size of the bang when the cylinder lights off. I read where in worst case conditions, temperature extremes could change your performance by as much as 25%. Soooooo if there is any truth in that number, not knowing what "at temperature extremes" means, your not getting 50 could have nothing to do with your engine's current condition; just that you had a data point one day and you haven't been able to duplicate the conditions and get it again..

You do know that your motor does not have the same ignition as the OP. His stator has both high and low speed windings which are known for.failing. It can also test good cold and fail warm But yes lets go.with the weather. Or.you can.keep.trying mechanic in the can, the solution of the terminally lazy and uninformed.Or if we go with my esteemed.colleagues theory, you could build a sun shade over your motor.