Jet Boat Build issues

[Ned L]

Re: Jet Boat Build issues

Neat project! My first thought on seeing it was to wonder if you were going for a Jersey speed skiff 'look'. Sorry I can't help you with this, but if you ever get into speed skiffs let me know!

 

[junkraft]

Re: Jet Boat Build issues

If I could afford a Speed Skiff, I wouldn't be screwing around with this project. LOL!! This was supposed to be a low budget project but I should know better by now. As far a removing the oil pump and replacing it with a block off kit...I prefer it this way over the throttle body injection. I have had several 2 stroke bikes with true cylinder/crankcase oil injection and had no issues. The stock dribble in injection may be OK but now I know what I getting for lube with the gas/oil mix. (Castrol twc3 mixed 24:1......I've been running this mix for years in all my 2-stoke applications without and problems). The blank off kit let me get rid of the oil tank . I also removed the worthless choke butterfly and installed a primer system which works great.....and I know it's getting lube on start up vs straight gas. It cranked excessively with the choke system....tough on the starter and battery. A cylinder hone/ring job is still needed (122/145) to make this engine fresh. I have a tach to install before the next actual run and impeller inspection is a given. But it still boils down to the fact I need a 760 and new impeller. Time to part with some of my toys so I can continue.
Thanks again for all your replies!

Buzz in VT

 

[junkraft]

Re: Jet Boat Build issues

It was earlier stated in a few replies that the OEM units were not that good and a stainless unit would be far better...........I'm only going by what I'm told. Anybody got a good reasonable complete 760 they want to part with?

 

[junkraft]

Re: Jet Boat Build issues

I'll try to get to it soon......what should I have?

Thanks

 

[smokeonthewater]

Re: Jet Boat Build issues

LOOK and see if you have a stock impeller... you MIGHT not 24:1 is way too much oil... that engine should get 50:1

 

[NYBo]

Re: Jet Boat Build issues

24:1 is way too much oil... that engine should get 50:1

Yeah, and that may be contributing to your problem.

 

[junkraft]

Re: Jet Boat Build issues

The saga continues......I went and retrieved the boat from storage and pulled the impeller and shaft. It would bug me all winter If I hadn't.
Anyhow, the impeller has some cracks (fatigue?) and some dings. Wear is probably typical for a 21 year cast aluminum unit. I will replace it. The "wear ring" doesn't look bad. Max clearance to the impeller is about .030". I don't know what new would be. Attached are a few more pics for you to analyze. The drive needs to be refreshed. Rear bearing and grease are like new. I have to get the tool to hold the shaft so I can unscrew the impeller. As far as the 650 goes, I plan on doing a cylinder hone/ring jog and see what that buys me.
I couldn't find any #'s on the impeller so I assume it is OEM.....I'll look for an equivalent Solas or such. Thanks for all your feedback.
I have some early build pics that I'll post to show how this nonsense started. Maybe tomorrow.

Buzz in VT

 

[junkraft]

Re: Jet Boat Build issues

....some more impeller pics.

 

[smokeonthewater]

Re: Jet Boat Build issues

that IS a stock yamaha impeller .. they were junk when brand new... one of the worst impellers I've ever encountered

I think you need to choose a path before you go much further... there is no way you are gonna get 30+ mph with the 650 so if you want speed you need an engine... personally I would STRONGLY consider looking for a smokin deal on a yamaha or kawasaki 900 or 1100 ski over the winter (with the adapter brackets it's still a bolt in swap).... would be a shame to swap out impellers TWICE as you will need a far different pitch if you more than double your horsepower

 

[junkraft]

Re: Jet Boat Build issues

For those who followed this thread, Thanks again for all the feedback. I installed a new Solas 14-17 impeller yesterday. Nice fit in the ring with an eyeballed clearance of <.010" . It all looks good. Next step is to freshen the top end of the 650 in the spring and see what I end up with. A plan to move the controls and seating has been created, but I still like the Jersey Speed Skiff look. But time will tell.
Any of you who have built a conversion like this, or if you know of someone who has, feel free to contact me direct.
Thanks again!
Buzz in VT

 

[junkraft]

Re: Jet Boat Build issues

I finally found the SD card with some of the early build pics. Here are the first 5

 

[junkraft]

Re: Jet Boat Build issues

........and 4 more

 

[Brian 26]

Re: Jet Boat Build issues

Love the build project. You should check out the PWCToday.com, they have a build section where guys have done jet conversions like this.

Putting a new top end on a crankshaft that is 20 years old may cause the lower end to fail. But that might not be all bad as you'll be able to use the time to decide if this motor is big enough or if you want to find a bigger engine out of a parts ski. If you are going to look on ebay for engines be careful who you buy from, used ski parts on there are a big gamble, lots of shady sellers selling junk.

Thanks for posting the pics and keep us up on how it goes.

 

[moosehead]

Re: Jet Boat Build issues

The tight tolerances to the wear rings are plenty enough to be the issue, but add the pitting and damaged edges from the impellar, and replacement alone may be your solution. The stainless wear rings provide for precise tolerance and for more durable wear from debris, sand, & sticks getting pulled into the jet, but critics suggest a composite ring can take the damage leaving the impellar better off.

It is hard to see where the intake grates sit on the hull bottom, so this also still could be a challenge if she is nose high due to a heavy stern.