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914Driver MegaDork
7/24/20 8:10 a.m.

I almost screwed this up before it got going!  Laying in bed staring at the ceiling, I had almost MacGuyvered mounting the engine to the hull - - then I read your thread.  Simple genius, or is it geniusly simple?  Cut & Paste. 

someone New Reader
8/8/20 8:07 p.m.

am not trying to high jack this thread ,i  actually got inspired by this build . and i really thank toyman for his good work detailing everything.

so i got a a 99 xl with carb issue but everything else looks good .

so donor car check , donor ski check , now hunting for a hull once i get a hull i will start a new thread .

the only thing to think about is that the xl engine weight even less than half of the kia engine . but the kia engine is at least 5 time more reliable and starts every time .

HP and weight are pretty important in a boat. 

That said, if I build another one it will have a 4 stroke. Probably the drive out of a Yamaha FX Cruiser which is 1.8L.

someone New Reader
8/11/20 6:46 a.m.

In reply to Toyman01 (Moderately Supportive Dude) :

A fresh build 4 stroke should last at least 400 hours, which is very good. 

I would like to ask you for the  hull, which is better a bayliner style hull or a fiberglass skiff like this one 

In reply to someone :

It really depends on what you want to do with the boat. 

I used a small skiff because I wanted to be able to go places my bigger boats couldn't go. It will run over logs in the rivers and run in water down to about 6" deep. I can run through a stump infested area of the lake without worrying about hitting them. Basically, if I can't see it, I probably won't hit it. 

If it's going to be your primary boat, something like the Bayliner might serve you better. It will hold more people, ride better and handle the waves in large bodies of water better. The trade off is the deep V hull will draw more water in all situations. 


miken92 New Reader
8/28/20 10:50 p.m.

Can you say cleaner

Toyman! MegaDork
7/17/22 6:30 p.m.

So, bringing this one back from the dead. 

Son number 2 wanted to use the JetBoat over the 4th so we dug it out from behind the shop. Hooked up the hose and it wouldn't turn over. Sounded hydro-locked. He pulled the plugs and sure enough, one cylinder was full of water. Fresh clean water that had to have come from the hose. That afternoon we blew all the water out of the engine and got it running long enough to flush some fuel through the engine and get enough heat in it to dry things out. 

Today we tackled the problem. We got it running and turned on the flush water again thinking it may have had a plugged exhaust that back flowed into the engine. It ran fine and stayed cool, but the primary muffler was leaking out of the bottom. 

He pulled the exhaust and it turned out to be a complete mess. Lots of corrosion in the water jacket. Two places where the inner jacket was corroded through and one where the exterior jacket was corroded through and lots of areas where the water passages were practically blocked by corrosion and salt crystals. I'm pretty sure we found where the water was coming from. 

The leak.


That's just nasty.




We were off to the internet searching for parts. Surprisingly enough, they are still available from Yamaha if you can afford them. Including the gaskets and such, this pile would set you back about $500. 

Our friendly Ebay has used stuff and if you are careful where you buy it you can get parts from a freshwater ski that work like new. The parts should be here Wednesday for a princely sum of $100 including freight. 

You may be seeing more of this throughout the rest of the summer so keep an eye out. 

wheelsmithy (Joe-with-an-L)
wheelsmithy (Joe-with-an-L) PowerDork
7/17/22 8:01 p.m.

One of my all time favorite GRM build threads. Good to see its longevity.

Floating Doc (Forum Supporter)
Floating Doc (Forum Supporter) PowerDork
7/17/22 9:48 p.m.
wheelsmithy (Joe-with-an-L) said:

One of my all time favorite GRM build threads. Good to see its longevity.


ClemSparks UltimaDork
7/22/22 10:04 a.m.

Just a couple weeks ago I re-read this thread in its entirety because I have an increasing urge to build a jet-jon boat project.  Glad to see this one cycling around in your rotation!  

(this is how my projects work too...they get attention when the mood strikes and might sit a year or 4 in between mood strikes ;))

Toyman! MegaDork
7/25/22 7:27 p.m.

The exhaust parts showed up. My son got them installed today. Engine problems solved. 


Next up is pulling the pump and resealing it to the hull. That will be tomorrow after work.

ClemSparks UltimaDork
7/27/22 8:58 a.m.

I think you mentioned insulating the engine compartment (for sound) earlier in the thread but I'm not sure if you ever got to that or mentioned it (you may have and I'm forgetting).  I thought I'd ask if you did insulate, what you used, and how it worked.  I love the concept of a PWC-powered boat but I know I'm going to be annoyed by the sound, lol.

Toyman! MegaDork
7/27/22 10:02 a.m.

In reply to ClemSparks :

I thought about insulating it but never actually did it. Sitting in front of the engine it's not too terribly loud. 


ClemSparks UltimaDork
7/27/22 11:24 a.m.

Cool...thanks for that.

Toyman! MegaDork
10/2/22 3:59 p.m.

The jet boat got some more maintenance today. It's had a persistent leak between the hull and the pump. This afternoon Second Son pulled the pump and resealed it to the hull. 

Zachary New Reader
7/30/23 11:44 p.m.

In reply to Toyman! :

Resurrecting this to say what an awesome thread and where is the project at now?

Toyman! MegaDork
7/31/23 7:34 a.m.

In reply to Zachary :

Glad you liked it. 

The project is currently behind my shop under cover. Unfortunately, we haven't had much time to play with boats this summer.

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