2003 Mercury 75 HP ELPTO outboard bogging down

[EVENING OUT]

Hello, I am new to this site. Trying to figure it all out. I have a 2003 Mercury 75 HP ELPTO outboard. I have had it a little over a year. Supposedly the outboard was rebuilt. Not a lot of known history on this pig. I do know I had the carbs cleaned and rebuilt prior to last summer. Before this season I have changed the water pump impeller and plates. Spark plugs changed, primer bulb changed. (not related but lower unit oil changed). The first time or two out on the water (salt), motor ran great, no issues. The last 2 times it idles fine and runs at WOT for about 5 or 10 minutes and then bogs down. We were close to where we wanted to just idled to the location we were going and hung out for the day. Motor starts right back up and again, runs about 5 to 10 mins and then bogs down. By then we are back at the ramp and on our way home. No issues running this pig in the driveway on the hose and muffs. Any ideas? today I removed the thermostat and the poppit valve. Can't tell anything by looking at the thermo, but I am picking up a new one tomorrow and replacing. The poppit valve diaphragm looked beat up and had some holes and roughage. Would the poppit valve cause the motor to bog down. I never had an overheat alarm, the tell tale was spitting nicely. Don't know if alarm work. I do have a water pressure guage and that is always about 10-20 psi depending on RPM's. I do have a temperature guage, but it never reads anything so I don't know if that works either. Also I did notice that water was expelling out of a small hole on the thermostat housing. See pics. Any advice would be greatly appreciated. Thanks.

 

[ThomW]

If it is happening after running for 10 minutes or so, it could be going into LIMP or SAFE mode as a result of the temp getting too high. A faulty or bad temp valve could cause the motor to switch into SAFE mode when it gets too hot. Alarms are only useful if they are working. When you say it "bogs down" what do you mean? Usually the SAFE mode will limit your engine to 2000-2700 rpm's or so. There is no picture posted to view the issue with the thermostat housing.

 

[EVENING OUT]

When i say it bogs down I mean i go from cruising 20-30 miles per hour to barely moving 10 mph. I actually didn't pay attention to what the RPM's were, I kinda just panic and get off the throttle. At that point i can idle about 5 mph or so. And site wont let me post pictures

 

[EVENING OUT]

BTW,
Thanks for the response.

 

[EVENING OUT]

No Title

the arrow is the hole that was expelling water. Thermostat on top right, poppit valve and diaphragm on right with spring

 

[EVENING OUT]

No Title

whole set up

 

[Maclin]

Does it run on an internal or an external tank? Proper venting?

 

[EVENING OUT]

Internal tank. Though, after I put the new thermostat and poppet valve in I will be bringing a separate small tank with me so that if the problem persists I can switch my gas source and eliminate the gas tank and consonants being the issue.

 

[Maclin]

On a boat I just sold, 90hp Mariner outboard and internal tank, the previous owner said he put a new primer bulb in. It worked ok but every once in a while it would not pump up. And once out on the lake it stopped letting fuel draw through. I replaced it with a quality brand name unit, the new one had much more pronounced ribs on the outside and pumped up every time like a boss. Never had the fuel issue after that, several seasons.

 

[EVENING OUT]

No Title

Ok, I changed the thermo and poppit. Took it out, still noticed slight overheating, but going into "safe mode". Brought it back home, thought it was the tube from the water pump so checked that and decided to check impellar while i was at it. Impeller was just changed early june, it was cracked on every spline. Anyone know what would cause this? Anyway, boat ran like a champ after. Thanks for all input.

 

[MH Hawker]

i would guess it was ran dry

 

[Maclin]

Looks like yes, run dry, and some exhaust heat came into play at some point as if not all rubber isolating grommeting/gasketing was reinstalled correctly. Was the pump housing ok, not warped?

 

[EVENING OUT]

Thanks guys. It was never run dry. I believe it was a cheap impellar. The guy refunded me for it. I went to west marine and got a quicksiver impeller and installed it. The housing didn't look warped or have any sharpness. The metal gasket and other gasket were both new. She is running good now. I did learn another thing. Oil got down to about a quart and engine went into "guardian" of "safe mode" again. I added oil and she's still running strong. Never ending I guess. lol.