Identifying the undeterminable? Tohatsu 18?

[TwoRivers]

I picked up what's suspected to be an 18hp Tohatsu 2 stroke motor with a bad powerhead. The reason I went for it was that I have a 9.9B2 and I figured some of the parts were interchangeable (I needed a starter).
Looks like the flywheel and the pull start mechanism are the same and the transom mount is intact. Tiller handle, prop, shifter all look the same. Carb set up is different so is the ignition and it has a larger engine cover that looks cool & fits my 9.9.

I pulled the head cover off the powerhead and determined that one of the pistons gouged up the lower cylinder. The motor is not locked up. I'd like to tear into this thing more but I'd like to have a factory manual first (just in case I want to put it back together).
Getting it running again will be secondary to learning how these things work.
The issue is that there is no tag on the motor to indicate the model & serial #s. The old gent that I bought if from said that he removed the tag and changed the decals on the motor to 9.9 in order to run on limited HP lakes in PA.
He thinks he bought the motor new around 99 or 2000 but can't be sure.

To anyone's knowledge, is there a way to determine the model & serial #s? Do they exist elsewhere on the engine?
I also need a factory manual for my 9.9 B2, will the manual also cover 18 hp models?
Will pictures of the motor help anybody?
Thanks in advance for your comments.
Anybody know where to find an 18 powerhead ?

 

[Sea Rider]

Re: Identifying the undeterminable? Tohatsu 18?

15/18 HP have a larger throttle cam compared to the 9.9 model. Check Pics. You could have a 15 or 18 HP, although share same size block, 18 has slight bigger pistons and impossible to determine by external view.

The engine must have a small round thin plate where numbers are stamped at, check throttle side at block's middle side, sometimes it falls off so probably not there. If being a 18 go for a repair, can place next size 0.5 mm pistons and bring back to life that cool horse. Factory service manual covers all 2 strokes single carbed engines up to 40 HP.

This is an 18E2 model. Place internal side pics of yours to compare. Include cam/carb views.

Happy Boating

 

[TwoRivers]

Re: Identifying the undeterminable? Tohatsu 18?

Thanks Sea Rider for your reply and the pics. That sure looks like what I got minus the elec. start. I'll post some pictures later.
I'm going to get a manual, but, if I can get ahead of myself for a moment? If the 9.9, 15 & 18 blocks are all the same then I can look for any of these powerheads and it's possible to have a 9.9 or 15 turned out to 18 hp specs? And I guess the option for repairing my block is a new cylinder sleeve and piston?
Again, way ahead of myself but it's winter here and the wrenches start to wander.
Thanks again.

 

[pvanv]

Re: Identifying the undeterminable? Tohatsu 18?

Any dealer (including me) can provide the Factory service manual you need. Part # 003-21035-1, $45.00.

 

[Sea Rider]

Re: Identifying the undeterminable? Tohatsu 18?

9.9 & 15 HP are 250 CC, 18 is 300 CC has slight bigger pistons. If can't be sure if you have a 15 or 18 HP, remove one piston and measure it's diameter or cylinder wall circumference. That data is probably in the Service Manual. Then you will know. Will need to buy a 0.5 piston and that's it. You can convert a 9.9 into a 15 but not a 9.9/15 into a 18 without widening the cylinder wall.

Happy Boating

 

[TwoRivers]

Re: Identifying the undeterminable? Tohatsu 18?

I think I'm starting to get it. The block (lower end) is the same but the powerheads are different?
Anyways, would a repair require a new cylinder sleeve in addition to a pistion to repair the gouged cylinder wall?

 

[Sea Rider]

Re: Identifying the undeterminable? Tohatsu 18?

Visually speaking D2/E2 power heads are same, but not internally, E2 have piston and cylinder wider diameter differences compared to 9.9/15 HP . By gouged you mean, severely damaged, with deep scratches, lines piston marks, etc ? If not that deep and with enough wall thickness to be widen a bit at a machine shop a 0.5 mm piston will be accepted and work. If too deep for a 0.5 mm piston, sleeves will be the way to go or buy a second hand in good condition block.

Happy Boating