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1995ish 18HP Tohatsu - Lower Unit Removal

Printed From: The Fishing Website
Category: General Forums
Forum Name: The Outboard Clinic
Forum Description: Anything related to outboard maintenance here....
Printed Date: 07 Feb 2023 at 5:52pm

Topic: 1995ish 18HP Tohatsu - Lower Unit Removal
Posted By: tohatsu
Subject: 1995ish 18HP Tohatsu - Lower Unit Removal
Date Posted: 17 Jun 2022 at 3:18pm
 A few years ago a guy doing a routine servicing of the motor said he was unable to remove the lower unit to phyically check the pump impeller. He said that the pump was operating normally so that it didn't matter at the time but that I might need to bring it back when the pump failed and that he might need to go in from the top.

I have seldom used the boat since but I am considering selling and I tried to remove the lower unit myself but it seems solidly on. I thought that some penetrant might help so tried spraying wd40 on the joint a few times but that didn't help. I am happy that there are only four bolts to be undone so am presuming that there is some corrosion welding the unit in place.
My questions are..

1. Is there a better penetrant to use and what else could I try?
2. Any idea what the costs might be to go in through the top? 

Any suggestions would be welcomed.

Model is M18D 350A.


Posted By: Kandrew
Date Posted: 17 Jun 2022 at 6:36pm
Sounds like the drive shaft is stuck in the bottom of the crankshaft, happens and normally spraying penetrating oil up there won’t work. Going in from the top means taking the power head off or even apart to get the the bottom of the crankshaft, bit of a job and if you haven’t had one to bits before. You can do some damage if you get things wrong. Pretty hard to put a price on it, if they have to strip the power head down to get the crankshaft out it will be expensive.

Where are you based

Posted By: smudge
Date Posted: 17 Jun 2022 at 6:44pm
I am not familiar with Tohatsu outboards but there is usually a 5th bolt under the trim tag anode. Make sure you mark it before you take the trim tag off or your boat will pull to one side. If the bolts wont come out dont force them. Use some heat

Best gurnard fisherman in my street

Posted By: tohatsu
Date Posted: 17 Jun 2022 at 8:39pm
Hmm, thanks for that. I am in Wellington, Eastern suburbs.
I must google that thing regarding the shaft.

Posted By: tohatsu
Date Posted: 17 Jun 2022 at 8:42pm
I will double check for that additional bolt but my impression was that the 4 bolts were all that was holding it on. Cheers.

Posted By: smudge
Date Posted: 19 Jun 2022 at 12:03pm
I just watched a how to video on replacing the impellor on a Tohatsu and it looks like you're right, on the video I watched it was only four bolts holding the gear case on

Best gurnard fisherman in my street

Posted By: tohatsu
Date Posted: 28 Sep 2022 at 7:30pm
Hi All

First a response to "Kinger" whose reply to me has not yet shown up on the forum - I have indeed released the shifter shaft linkage.

However I did get a bit annoyed with the engine and stopped using a small knife to force an entry and started using several large knives, a machete and some vaguely triangular shaped bit of metal from an old wood plane. I also stopped using a small hammer and started using a small sledge.

That lot plus 2 cans of wd40 finally did the trick and the lower unit is now showing a 50mm gap. I have stopped at that point to watch the various Youtube videos on the subject again before I get the parts etc to replace the impeller. I will be interested to see exactly what caused the lower unit to freeze once I completely remove it.

Thanks for the suggestions.


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