Low RPM & Speed with Merc 200

Duke01 · #1 09-24-2020, 04:43 PM

I took the Welly out on Lake Erie last night, it had been a month since I had started the engine and 3 months since I had her out on the water (the motor yacht always seems to get more attention - no surprise there). The old Merc started right up, ran smooth, all good except I maxed out at 20 MPH and 4000 RPM. Tried 4 times and never exceeded 20 MPH. I pumped the bulb for a 2nd and 3rd time, same results. So, I am thinking maybe a bad fuel pump, or perhaps a possible leak in the fuel line? I am going to install an inline fuel pressure gauge and check the tank vents too.

It is a 1980 motor, so the fuel pump (88853A1) does net seem to be available (?)

I welcome any input from the group.

Thanks, as always, Duke

phatdaddy · #2 09-24-2020, 06:23 PM

Easiest thing to do first is check fire on all cylinders, check plugs and compression while at it.

THEFERMANATOR · #3 09-24-2020, 08:19 PM

Sounds more like a weak stator or switch box to me. If it was the fuel pump, it eould normally take off abd then fall on its face as it sucks all the fuel out of the bowls. Have somebody pump thr primer bulb while it won't turn up, if it picks up rpm's then I would look at the pump. Those early pumps are nla, you would have to try and rebuild it, or go to a newer style pump. To me this sounds most like a high speed stator on its way out.

Duke01 · #4 09-24-2020, 08:39 PM

Thanks guys, after doing more research, it does sound like the stator. I will take her out again after I check the plugs and install a fuel pressure gauge and new fuel filter. Then pump the bulb as you suggest Ferm and see what the impact is, if any.

Stator was replaced in 2011, along with the switchbox by the previous owner. I thought that I had that part behind me...perhaps not.

spareparts · #5 09-28-2020, 06:56 PM

compression test, spark check, fuel check, report back with results

Duke01 · #6 09-29-2020, 04:55 PM

I will perform those checks this weekend, weather permitting.

Thanks, Duke

Duke01 · #7 10-09-2020, 02:55 PM

Root Cause: Zebra Mussels

Yes, what I thought was a engine mechanical issue was the drag created by a couple thousand zebra mussels. No bottom paint on this boat since I intended on rack storage this year, but due to Covid, the rack storage building was full, and the marina fork lift had mechanical issues. So, I kept the Welly in a slip. I expected a power and acid wash at the end of the season, but I but not expect the mussels. I had her in Lake Huron last year – no mussels issue there. Anyway, I wanted to follow-up. Sorry for wasting your brain power on my screw-up.

phatdaddy · #8 10-09-2020, 07:29 PM

Well good news , i guess. Don t know whats involved in cleaning bottom, but i think I d rather it had been a switch box.

Take some pics never seen them before

Duke01 · #9 10-11-2020, 02:33 PM

Here are a couple of pics via Imgur:

https://imgur.com/R9NHx4D

They probably only weighed around 20 lbs, but they created quite a resistance at 20 mph. Power washed for 3 hours, still need to hit it again with a hull cleaner. I was using an acid hull cleaner from Starbrite, but it was too windy for that nasty stuff. I just ordered a bottle of the non-acid hull cleaner from Booyah. Curious how well it will work.