Merc Inline won't pull up skier

**kswiatk** · 08-19-2019, 09:44 AM

I have a mercury inline SN# 641xxx 115hp on a Baja Sport 16ft with closed bow, that cannot pull up a slalom skier.

It will lug and just stay at 2800/3000 rpm and just drag them through water. We have been resorting to starting with doubles and dropping a ski. It also hangs around that rpm with doubles, but eventually pulls them out. This has been with just two people on the boat.

Here a bit more info the setup and what i have done so far.

49 mph gps at about 5500 rpm with 13x19 prop
46 mph gps at about 5800 rpm 13.23x17 prop. Drilled 1/8 in vent holes in prop to try and help acceleration, no difference with skier.

Vent plate about an inch above the bottom. Trim limit pin removed and engine tilted all the way down.

PHD is re-ringed new this season, has 120 psi all around as of two weeks ago.

Trigger, stator, swithchboxes, rectifier replaced in order to fix charging / spark issues. All test good on gap tester and DVA.

Carbs rebuilt start of season. Floats are good, height is correctly set. I recently had an issue with a sticking needle on one carb.

Fuel pressure measured and pump rebuilt . Found a leak at the fuel line quick connect and fixed. Shows 3-4 psi at idle, falls to 2 - 3 psi when going onto plane, then raises once at speed. We have tried squeezing the primer bulb while it lugs, but nothing changes.

Link and sync, timing set. It accelerates great with no skier, does not die when the throttle is stabbed. I even opened up the screws an extra turn but no change for a skier.

The only other bad symptom is that the motor will die when going into in gear idle unless a bit of throttle is given.

Does anyone have any idea where else to look for issues on this thing?
I am going to change out the other two needles/seats since the other one had been sticking, but beyond that I'm not really sure what else would cause these high load issues.

**Dave S** · 08-19-2019, 11:12 AM

Playn with Fire.....What # are you running for max timing? Ya set it low to keep from burning pistons JMO you can set to low. If someone put in richer jets to save piston.....can cause probs. Stalling gear is low timing/carb mix...... or bad labraths on reed cages.....Sorry for crappy spelling.....Having it trimmed down? don't no if that is good or a thing you must do for ski...ing..My next thing I will say a V4 rude......HeeHee......Just kidding guys.

**LakeFever** · 08-19-2019, 11:34 AM

Drop prop pitch. Try a 15 with lots of cup

My 115 cross flow would yank your arms off with a 17p if you werent ready for it

**FMP** · 08-19-2019, 11:51 AM

Tell the skier to stand up

**kswiatk** · 08-19-2019, 12:04 PM

20 degree, carb jets are to the spec. I thought about dropping pitch, but was told this was not normal performance with a 17

**FMP** · 08-19-2019, 12:31 PM

A bit of slack and jump off the dock, hit the water moving.

**LakeFever** · 08-19-2019, 12:32 PM

Those inlines are not arm stretchers so give it all the help you can get. Tons of top end there for skiing you can drop way down it pitch imo. If the 15 doesnt do it try a 13 I sure wouldnt lean it out or try and win this with HP your going to spend a ton of time and money for little gains and risk burning your mota down. The right prop will solve this. You might want to find a local prop shop and work with them and see if they cant get one customed up to work well for you

**Capt.Insane-o** · 08-19-2019, 01:22 PM

Bores are probably tapered and the labyrinth seals worn. New rings do very little to cure that.

**LakeFever** · 08-19-2019, 01:28 PM

Originally Posted by Capt.Insane-o

Bores are probably tapered and the labyrinth seals worn. New rings do very little to cure that.

Your tech knowledge of everything Merc is incredible

**Capt.Insane-o** · 08-19-2019, 01:49 PM

Ive ownedl a merc since i was 8 years old...so closing in on 40 years. I've rebuit many many many inlines fresh bores and use automatic transmission seals in the labryth seals and they run like a top.