TOPIC: Question on upper cowl, 64 Merc 650

I notice that I get a fair amount of exhaust fumes in the cockpit when underway. Part of it is the boat's design, the cabin/windshield creates a low pressure area that pulls the motor fumes forward. But, I also notice that this motor has the wrong upper cowl, from a different year. The graphics are red, not black, the exhaust relief port has been added with a grinder, and the cowl doesn't really match up correctly to the bottom of the motor. Wondering if that's part of the reason for all the fumes. At idle/trolling speed, I see no exhaust at all coming from the prop hub. It's all venting from the relief port. Is that normal? At speed, there is exhaust coming from the prop hub but still a lot of venting from the port. No fumes from inside the engine cowl though. Is it possible the wrong cowl would lead to excessive fumes venting from above waterline? See photos, yup the paint is awful, haven't done a thing to the motor cosmetics since I got the boat.

that would not be the problem the original cover was a thin flat piece not cast. the problem might be the seals on the upper mounts.

I just parted out a 1963 Ser# 1544592. Check the marineegine.com site and see if it used the same cowling.

I have the whole cowling top to bottom I will let go at a good price

Thanks guys. (I posted a reply yesterday but it got lost in the ozone...)
Dave, I'm guessing those seals would require removing the powerhead to replace?

Allan, I never did see the original part, it was replaced before I got the motor. Looks like it's the one labeled, "Cover, trim, driveshaft housing". When you parted out the 63 motor, do you still have the powerhead we discussed?

yes it would . try silicone on the outside. may work.

I'm currently working on the exact same motor, Trying to find a starter rebuild kit, and also going to rebuild the wire harness and hoping like hell the stator is ok... any pics you want me to take of mine, feel free to ask.

Thanks for the offer Joe.

Dave, I've been looking at the parts diagrams on Marineengines.com and can't pin down the seals you mentioned. I see two gaskets, driveshaft housing to bottom cowl and powerhead to bottom cowl. Are those the ones?

www.marineengine.com/parts/mercury-outboard-parts/650-4-cyl/1542745-thru-1765043/drive-shaft-housing-assembly

www.marineengine.com/parts/mercury-outboard-parts/650-4-cyl/1542745-thru-1765043/bottom-cowl-assembly

My son and I spent yesterday trolling and the fumes were pretty bad when heading upwind. Other than that, the motor ran well.

on the top one ##33 is the part.

OK, I see it. They're calling it upper mount packing. Thanks.

Normspeed wrote:

Thanks guys. (I posted a reply yesterday but it got lost in the ozone...)
Dave, I'm guessing those seals would require removing the powerhead to replace?

Allan, I never did see the original part, it was replaced before I got the motor. Looks like it's the one labeled, "Cover, trim, driveshaft housing". When you parted out the 63 motor, do you still have the powerhead we discussed?

Yes. I even pulled the broken bolt out. Lost 4 threads, however there are still 11 more to pull a bolt. It was for holding the exhaust tube on. I can drill it out and install a heli coil, however they will only give you 8 threads max.

Hate to say this, however I need to be rid of it for I have many many motors to get going for the Red River Flotilla (and it is taking up room and I will not store it outside). Let me know something in a week or 2. if not I am going to put it on the Bay for the starting price the price I told you.

I have a thin sheet of metal that strap around the back of the motor with Mercury(I think)on it...I will take some photos tomorrow.