Reply
 
Thread Tools Search this Thread
 
Old 08 September 2014, 19:24   #101
Member
 
Roflhat's Avatar
 
Country: UK - Scotland
Town: Isle of Lewis
Boat name: Macleod Special
Make: Ceasar Thundercat
Length: 4m +
Engine: Yamaha 70ces
Join Date: Jul 2010
Posts: 1,189
RIBase
Looks like i didn't gain any RPM with the exhaust mod. Sounds better and acceleration is considerably better but the top speed remained the same.
I had a fiddle with the timing while I was out today but advancing or retarding it from standard both seemed to make it slower. What I can say is that putting the ignition closer to 24* made the acceleration even better, and that the other way made it worse. Makes me wonder why it didn't help the top end though..
__________________
Roflhat is offline   Reply With Quote
Old 16 September 2014, 11:43   #102
Member
 
Roflhat's Avatar
 
Country: UK - Scotland
Town: Isle of Lewis
Boat name: Macleod Special
Make: Ceasar Thundercat
Length: 4m +
Engine: Yamaha 70ces
Join Date: Jul 2010
Posts: 1,189
RIBase
Couple pics of my new engine:



Just bought it yesterday and not yet arrived at the house. Unfortunately I'm off to uni for 3 months so won't be able to try it out for a while!
It's a Yamaha 70 which has been shortened and with a CES 'box on it. Just been rebuilt by a marine engineer, should be good to go. Came with an 11x21g yamaha cleaver. Need to get a tiller for it, going to try and adapt one of our old hydraulic steering systems to go on as a damper. Will be staying electric start for now until I can source parts to convert to pull start.
__________________
Roflhat is offline   Reply With Quote
Old 16 September 2014, 11:45   #103
Member
 
lukewhiting's Avatar
 
Country: UK - England
Town: swanage
Make: Thundercat
Length: 4m +
Engine: Tohatsu 50
Join Date: Apr 2012
Posts: 968
Nice! What would you be doing with the tohatsu??
__________________
lukewhiting is offline   Reply With Quote
Old 16 September 2014, 16:35   #104
Member
 
Roflhat's Avatar
 
Country: UK - Scotland
Town: Isle of Lewis
Boat name: Macleod Special
Make: Ceasar Thundercat
Length: 4m +
Engine: Yamaha 70ces
Join Date: Jul 2010
Posts: 1,189
RIBase
Quote:
Originally Posted by lukewhiting View Post
Nice! What would you be doing with the tohatsu??
Think I might have to be selling it unfortunately! Yamaha still needs a lot of parts to make it work on a thundercat.
__________________
Roflhat is offline   Reply With Quote
Old 22 September 2014, 16:00   #105
Member
 
Roflhat's Avatar
 
Country: UK - Scotland
Town: Isle of Lewis
Boat name: Macleod Special
Make: Ceasar Thundercat
Length: 4m +
Engine: Yamaha 70ces
Join Date: Jul 2010
Posts: 1,189
RIBase
engine arrived today:






prop is absolutely mint as well


__________________
Roflhat is offline   Reply With Quote
Old 24 December 2014, 19:13   #106
Member
 
Roflhat's Avatar
 
Country: UK - Scotland
Town: Isle of Lewis
Boat name: Macleod Special
Make: Ceasar Thundercat
Length: 4m +
Engine: Yamaha 70ces
Join Date: Jul 2010
Posts: 1,189
RIBase
Got the wingplates off, had to remove the powerhead to get the bolts out...
Tiller is on, although the cables aren't connected.
The throttle cable on the engine is pull to open, whereas the tiller is push to open. Think I read somewhere about reversing a gear inside the tiller to fix this? Anyone know? I also appear to be missing a bracket of some sort to hold the cables in place, going to google it and see what I can find.
Looking at the engine more closely it looks like it is a genuine CES, or 90% CES parts, Here's a couple photos of what I mean about the cables.



__________________
Roflhat is offline   Reply With Quote
Old 05 May 2015, 10:30   #107
Member
 
Roflhat's Avatar
 
Country: UK - Scotland
Town: Isle of Lewis
Boat name: Macleod Special
Make: Ceasar Thundercat
Length: 4m +
Engine: Yamaha 70ces
Join Date: Jul 2010
Posts: 1,189
RIBase
Got myself a set of 90 carbs, bought the reed chest plate as well just in case the throttle linkage doesn't work. The roller for the throttle cam is on the bottom carb of the 70 and the middle on the 90. Photo of them on the 90:

__________________
Roflhat is offline   Reply With Quote
Old 07 May 2015, 12:48   #108
Member
 
Country: Hong Kong
Length: 10m +
Join Date: Oct 2014
Posts: 63
Saw you are running NGK plugs. They are good but I don't think they have as far of a reach into the combustion chamber as some of the others. Also, not sure what yours requires but you might try the ones without the Interference Suppression Resistor to open your gaps.
__________________
Neuner is offline   Reply With Quote
Old 07 May 2015, 12:56   #109
Member
 
1eyedjim's Avatar
 
Country: UK - England
Town: Birmingham
Boat name: Sparrowhawk
Make: Osprey
Length: 5m +
Engine: Yamaha 90hp 2T
Join Date: Apr 2010
Posts: 215
I would want to check how's he space there is at tdc before sticking longer reach plugs in. Lad I know did it on a Jetski and blew his engine in minutes
__________________
1eyedjim is offline   Reply With Quote
Old 07 May 2015, 13:02   #110
Member
 
Country: Hong Kong
Length: 10m +
Join Date: Oct 2014
Posts: 63
Quote:
Originally Posted by 1eyedjim View Post
I would want to check how's he space there is at tdc before sticking longer reach plugs in. Lad I know did it on a Jetski and blew his engine in minutes
Everytime I've compared NGK plugs to other plugs that are made OEM (stock) for the engine, they have been shorter. I'm not saying to look for longer plugs but that NGK tends to always run shorter than others even when built to specs.

If your friend ran longer plugs without measuring, then he is a fool.
__________________
Neuner is offline   Reply With Quote
Old 07 May 2015, 18:21   #111
Member
 
Roflhat's Avatar
 
Country: UK - Scotland
Town: Isle of Lewis
Boat name: Macleod Special
Make: Ceasar Thundercat
Length: 4m +
Engine: Yamaha 70ces
Join Date: Jul 2010
Posts: 1,189
RIBase
Yeh you have to be careful with the spark plugs.
for tohatsus with standard heads you can run BR8ES, the E is extended so it reaches further in. But with a shaved head for more compression you need to be running BR8 standard length or else you risk having problems.
Need to check the 70 still to see which ones will work best. I usually run the Iridium plugs. You can check for interference by putting the plugs in and slowly turning the engine over by hand, then check if the pistons have hit them.
__________________
Roflhat is offline   Reply With Quote
Old 07 May 2015, 20:12   #112
Member
 
Country: Hong Kong
Length: 10m +
Join Date: Oct 2014
Posts: 63
Majority of the time I see the profs running a simple copper plug without internal resistors. You can have a larger gap and get a larger, hotter spark but if you don't have a coil that can handle it, it will fry.

In a different application, I ran a better coil, copper plugs and a greatly increased gap. Made enough of an improvement to note. Also improved my efficiency.

Just trying to help if you hadn't already gone down that route yet.
__________________
Neuner is offline   Reply With Quote
Old 08 May 2015, 09:04   #113
Member
 
Roflhat's Avatar
 
Country: UK - Scotland
Town: Isle of Lewis
Boat name: Macleod Special
Make: Ceasar Thundercat
Length: 4m +
Engine: Yamaha 70ces
Join Date: Jul 2010
Posts: 1,189
RIBase
i've not looked into it much, sounds interesting though
__________________
Roflhat is offline   Reply With Quote
Old 11 May 2015, 13:01   #114
Member
 
Country: Hong Kong
Length: 10m +
Join Date: Oct 2014
Posts: 63
Just remember, it only takes three components, Gas, Air & Spark and boom you got fire. Looks like you put a lot of work and time into two of them. I think the third is your next step. The bigger and hotter the spark the better and quicker the boom.
__________________
Neuner is offline   Reply With Quote
Old 11 May 2015, 20:29   #115
Member
 
Roflhat's Avatar
 
Country: UK - Scotland
Town: Isle of Lewis
Boat name: Macleod Special
Make: Ceasar Thundercat
Length: 4m +
Engine: Yamaha 70ces
Join Date: Jul 2010
Posts: 1,189
RIBase
Not sure I completely agree with you there. A quicker spark is less than desirable unless you're trying to advance your timing, which you can do by adjusting a linkage anyway.
__________________
Roflhat is offline   Reply With Quote
Old 11 May 2015, 20:33   #116
Member
 
Country: Hong Kong
Length: 10m +
Join Date: Oct 2014
Posts: 63
Quote:
Originally Posted by Roflhat View Post
Not sure I completely agree with you there. A quicker spark is less than desirable unless you're trying to advance your timing, which you can do by adjusting a linkage anyway.

Not sure you understand or how you got timing out of that. Not quicker, but BIGGER
__________________
Neuner is offline   Reply With Quote
Old 11 May 2015, 20:37   #117
Member
 
Roflhat's Avatar
 
Country: UK - Scotland
Town: Isle of Lewis
Boat name: Macleod Special
Make: Ceasar Thundercat
Length: 4m +
Engine: Yamaha 70ces
Join Date: Jul 2010
Posts: 1,189
RIBase
Quote:
Originally Posted by Neuner View Post
Not sure you understand or how you got timing out of that. Not quicker, but BIGGER
Sorry I misunderstood!
yeh I'll look into it for sure. I've got uprated - nakuru - coils (from a motorbike) and iridium plugs on it on the moment. So dyou reckon an increased plug gap would increase power?

Edit: looked into it, and apparently increased spark plug gap gives greater power except usually at WOT, when you may even want less gap to prevent misfire?
__________________
Roflhat is offline   Reply With Quote
Old 11 May 2015, 20:46   #118
Member
 
Country: Hong Kong
Length: 10m +
Join Date: Oct 2014
Posts: 63
Quote:
Originally Posted by Roflhat View Post
Sorry I misunderstood!
yeh I'll look into it for sure. I've got uprated - nakuru - coils (from a motorbike) and iridium plugs on it on the moment. So dyou reckon an increased plug gap would increase power?
It will to a certain extent. Haven't found anyone that has provided an equation or rules of application. More of try and test in gap steps starting at 1-5/1000 from where you are at. There are general guides that should get you started. Would guess diving into the performance motorbike world as a start? If you go too far, not sure what happens with your setup. Most likely misfires with your coils unable to produce an adequate voltage for the wider gap.

Getting a larger gap which is closer to the center of the gas/air mixture is what you want. This is why I was saying that I found the NGK plugs to be shorter than others when you compare them for the exact same application. In my testing, I found that a wider gapped NGK was equivalent to a normal gapped Champion because the Champion extended further into the chamber.
__________________
Neuner is offline   Reply With Quote
Old 11 May 2015, 21:52   #119
Member
 
A1an's Avatar
 
Country: UK - Scotland
Town: Fort William
Make: Ribcraft 585
Length: 5m +
Engine: Yamaha F115
Join Date: Mar 2012
Posts: 2,896
RIBase
Quote:
Originally Posted by Roflhat View Post
So dyou reckon an increased plug gap would increase power?
Its going to make about the same difference to the boats overall performance as emptying your bowels before climbing aboard.
__________________
There is a place on this planet for all of Gods creatures.........right next to my tatties and gravy.
A1an is offline   Reply With Quote
Old 12 May 2015, 07:30   #120
Member
 
Roflhat's Avatar
 
Country: UK - Scotland
Town: Isle of Lewis
Boat name: Macleod Special
Make: Ceasar Thundercat
Length: 4m +
Engine: Yamaha 70ces
Join Date: Jul 2010
Posts: 1,189
RIBase
Quote:
Originally Posted by A1an View Post
Its going to make about the same difference to the boats overall performance as emptying your bowels before climbing aboard.
That's the conclusion I'd come to to be honest! haha
__________________
Roflhat is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off




All times are GMT. The time now is 08:09.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2024, vBulletin Solutions, Inc.