1991 BlackMax 135 Hole Shot BOG

**ReidMarsh** · 02-26-2018, 06:39 PM

I am hoping there may be some input to this minor situation I have discovered. I have a 1988 Edson Avanti 17 with a 1991 Mercury Black Max 135 and the Prop is a Laser II 21P. The engine overall has been really well maintained and is clean as a whistle, starts up cold or hot as expected without issues for the most part and would consider the engine to be "Excellent" condition if I had to rate it.

Last summer I had noticed that upon occasion, not very often... the boat would BOG on the hole shot, with only myself, but once up and running was smooth as ever, the guages all look good and never misses a beat. When I would try pulling one of the kids skiing (100 lbs), I noticed I was running into the BOG each and every hole shot, and would have to feather the throttle up making a slow tough pull on them. I considered the prop but seems to be a pretty good overall performer and as mentioned gets up and goes more often than not without issue.

I run SHELL V Power (no ethanol), use Shell Nautilus Oil and had replaced the plugs with the oem spec and still the BOG rears it ugly head occasionally on my own and always under load with a skier.

P.S. The engine still has the factory Oil Injector, this will be removed this season.

Any thoughts would be appreciated!

**Motv18** · 02-26-2018, 09:54 PM

Solid plugs in the prop? swap them with smalls.
Could be other stuff, but 21 can be tough with 135 and a skier.

135 is in the need two props power range. One for running around fast and one for ski fun or capacity loads.

**Bruce2** · 02-26-2018, 11:18 PM

My 1995 135 was bogging on hole shot and i rebuilt fuel pump and now it jumps up and im turning a 23m on a 1150 dry weight bass boat @ 60 mph at 6100 rpm's, was turning a 25m but rpm's where only 5500@ 56 mph.

**mn808gade** · 02-27-2018, 12:31 AM

any popping/coughing at idle,check recirc hoses and unburned fuel dripping from them under electrical plate-th

**faztbullet** · 02-27-2018, 07:28 AM

If carbs have the accelerator pumps they could need replacing....

**billybob** · 02-27-2018, 10:29 AM

What I would try first is. when motor starts to bog. Push in on key switch, 1 or 2 sec. then throttle up immediately. If that helps it means you have a lean situation, causing bog.

**Steve Pope** · 02-27-2018, 02:05 PM

Replce the carbs with latter model wmv. Your wmh carbs have idle circuit located above float bowls and flood wheen accelerating when engine is tucked under. Wmv carbs have idles above carb throats and cant flood.