Volphin
Lieutenant
- Joined
- Jun 5, 2011
- Messages
- 1,405
My dad has an old 84 or so fish & ski with a Merc 115 I6 on it. (Serial 0B145105)
He just won't get rid of the old gal, so it's up to me to keep her running. 2 years ago the oil injection system failed so I removed it and plumbed her for a direct tank mix. She ran really well on 50:1. Early this season I noticed a lack of power over 3500 RPM. I figured I would wait until Fall to look at it as it was still running ok at lower RPMs, and dad and I only run about 1/2 mile down to our fishing hole and back.
Anyway, yesterday I pull off the cover and hook her up on muffs. All plugs are firing and easily clear a 3/8 gap with strong spark. Compression was great... 135-140 on all 6. Gas tank vent was clear. So I looked suspiciously at the fuel system. I have a cheapo primer bulb and gray line that can fail due to the inner liner. Possible. However, just for fun I decided to get a clear fuel filter at the auto parts store and run a few tests. (OE filter is not clogged). The clear filter filled with fuel while simply cranking the engine. However, I took her to the water and put a load on her and the fuel was not keeping up with the throttle. I could pop her up to 4500 rpm and then she would bog down. I observed the contents of the fuel filter drain away, and the motors lean out badly, protesting all the way. If I continue to insist, and bury the throttle, the most she will do is 3500 rpm. This was only for a few seconds and for testing only. I quickly returned to 2000 rpm to let the pump catch up. I have not put a fuel pressure gauge on the system. I really see no point. I believe fuel is not being delivered in the proper quantity to my carbs. So, I've never rebuilt a fuel pump on an OB before... is it as easy as the YT channels say? Any pitfalls? Also, I can ID the main fuel pump (the square assembly) but what is the triangular assembly attached to it? How about the solenoid with vac lines to the carbs? See image attached.
He just won't get rid of the old gal, so it's up to me to keep her running. 2 years ago the oil injection system failed so I removed it and plumbed her for a direct tank mix. She ran really well on 50:1. Early this season I noticed a lack of power over 3500 RPM. I figured I would wait until Fall to look at it as it was still running ok at lower RPMs, and dad and I only run about 1/2 mile down to our fishing hole and back.
Anyway, yesterday I pull off the cover and hook her up on muffs. All plugs are firing and easily clear a 3/8 gap with strong spark. Compression was great... 135-140 on all 6. Gas tank vent was clear. So I looked suspiciously at the fuel system. I have a cheapo primer bulb and gray line that can fail due to the inner liner. Possible. However, just for fun I decided to get a clear fuel filter at the auto parts store and run a few tests. (OE filter is not clogged). The clear filter filled with fuel while simply cranking the engine. However, I took her to the water and put a load on her and the fuel was not keeping up with the throttle. I could pop her up to 4500 rpm and then she would bog down. I observed the contents of the fuel filter drain away, and the motors lean out badly, protesting all the way. If I continue to insist, and bury the throttle, the most she will do is 3500 rpm. This was only for a few seconds and for testing only. I quickly returned to 2000 rpm to let the pump catch up. I have not put a fuel pressure gauge on the system. I really see no point. I believe fuel is not being delivered in the proper quantity to my carbs. So, I've never rebuilt a fuel pump on an OB before... is it as easy as the YT channels say? Any pitfalls? Also, I can ID the main fuel pump (the square assembly) but what is the triangular assembly attached to it? How about the solenoid with vac lines to the carbs? See image attached.
