Oil tank issues

[Bigbassfish]

Doing some maintenance tonight on my Opti 75 sn 1B791154 and I noticed a small amount of oil seeping out that I’ve traced to the connection between the oil tank and the throttle body, according to the factory manual it’s the #5 throttle body grommet but no part number. There was a little bit of oil sitting in the tank recess, and the seal was clearly darker and looked wet on the underside. It appear to be pinched but I can’t tell from the diagrams in the manual. It also looks like one of the throttle body bolts is rubbing pretty bad on the tank. Any guidance would be much appreciated!

[JOE54]

#5 seal p/n 891772002

[Bigbassfish]

Thanks! Does it look like it’s not properly seated on the bottom in the pics? I can’t tell if it’s leaking because it’s old and starting to crack, or if it’s just pinched up. Should I be concerned about the bolt rubbing on the tank?

[EuropeanAM]

Definitely not seated right in the picture.

[Bigbassfish]

Is it easy enough to reseat without completely tearing into it? Assuming there’s not an additional issue that needs solved with the throttle body bolt chaffing the tank, is it just a matter of loosening the oil tank bolts so I can wiggle it enough to reseat? As far as I saw it looks like just two bolts at the top holding the tank on. Would I need to do an oil pump prime after messing with this?

[Bigbassfish]

So thinking on it I’ve never done anything to my knowledge to have unseated the seal, must have been a previous owner or maybe from the factory like that? Would it be possible that this is evidence someone has done something in that area in the past that would’ve led to them reinstalling it incorrectly, and if this gives any clues towards the idle issue I’ve been having. As in, someone in the past trying to trouble shoot the idle issue leading to them removing the oil tank.

[JOE54]

Definitely not seated right in the picture.

+1 replace seal likely distorted

[FrancoCialone]

So thinking on it I’ve never done anything to my knowledge to have unseated the seal, must have been a previous owner or maybe from the factory like that? Would it be possible that this is evidence someone has done something in that area in the past that would’ve led to them reinstalling it incorrectly, and if this gives any clues towards the idle issue I’ve been having. As in, someone in the past trying to trouble shoot the idle issue leading to them removing the oil tank.

Have heard of 75-115 Optimax owners losing their plastic dipstick, break and fall into the oil tank, some tanks had a chain and some had a plastic unit mounted to the fill cap. In fact this happened to me and it was fixed at the dealer under warranty. They had to replace the dipstick, tank and seals. I removed the plastic dipstick, mounted under the fill cap, to prevent it from happening again, if you take the cowling off, the level is visable. Maybe the previous owner had that happen and removed the tank to get the dipstick.

[Bigbassfish]

You may be on to something…currently, the current cap only has about 5” of dipstick on it, I’ve heard of people just cutting it out but I think this one probably broke off, because if someone was going to bother cutting it, I’d think they would cut it all the way off at the cap. I’m assuming the tank will need to be removed to replace the seal, is this easier than it sounds? Sounds like if the tank has to come off, it might be a good time to try and fish out whatever might be left of the dipstick. Any advice on how to tackle this? I’m guess it’d be best to try and burn off as much oil as I can before pulling the tank.

[FrancoCialone]

After reading your reply, I found the dipstick the dealer replaced for my tank, its 13 1/2 inches long. At one end the dipstick has a mounting flange for the cap and at the other end it looks like a plastic arrow. Squeeze the arrow to install into the tank. I guess to prevent you from removing the cap and dipstick from the opening. When someone tries to remove it, the dipstick breaks. For the little amount of oil the 75 Optimax motor uses and how big the tank is, I could fill the tank 2/3 full and go half a season with it, I find it easier just to take off the cowling and check the level every now and then. Sorry I can't send you a picture of the new dipstick but I recommend not to remount it to the cap. I hope it works out for you pulling the tank.

[Bigbassfish]

So after further investigation, it looks like the throttle body bolt is seriously rubbing the tank as can be seen in the first picture, to the point I’m concerned it’s going to rub through. It also looked like at some point in time, the front of the tank had been rubbing on the cowling latch. I tried to see if I could loosen the oil tank bolts and slide the tank forward off the throttle bolt, but there was almost no play in the tank the the bolts loose. Could this just be a misaligned tank for the pinched seal?? Please advise.

[EuropeanAM]

I suspect it was misaligned the last time it was assembled and cowlings put back on.

[Bigbassfish]

So the solution would be to pull the tank, replace gasket and clamp, and then hopefully I’ll be able to carefully put it back on without any contact? Will it require an oil pump prime following removal of the throttle body gasket?

[Bigbassfish]

#5 seal p/n 891772002

Do you happen to also have a part number for the clamp? Anything else I’m missing for this?

[Bigbassfish]

From what I’ve read, as long as I don’t remove any of the hoses from the tank, I shouldn’t need an oil pump prime for reseating the grommet, is this correct?

[Bigbassfish]

Anyone want to chime in? I’ve finally gotten around to installing a new water pump, I’d really like to get the oil tank rubbing figured out before I hit the lake this week for some testing, I’m nervous about it rubbing a hole and being out $500 for a replacement. Seems like even if I don’t run the motor, every bump trailering to the lake will cause it to get worse.

[JOE54]

clamp #804842001,, correct on they oil prime

[Bigbassfish]

Thank you!! Working on getting the parts ordered, tonight I’m going to attempt to reseat it on the old seal and atleast get the tank to stop making contact.

[Bigbassfish]

I was able to remove the lower cowling and oil tank bolts and get the old seal reseated and it looks like the throttle body contact is gone! Reseating the seal brought the tank forward enough it was making contact on the upper cowling latch, but I was able to just loosen the bolts and pull the latch forward. Thanks a ton for all the help!! The replacement seal I ordered is on backorder, so hopefully this fixes it until then. When I replace the seal, I’m planning on taking some jb weld and trying to fill the divot that was rubbed in the tank, it seems damn close to poking through, but the tank is still holding pressure so fingers crossed!

[EuropeanAM]

Be very careful about the "JB"... last thing you want is something that could come loose and find it's way into the throttle plate.