Yamaha 30CV and 8hp telltale comparo

[Ally410]

Hi all, first post so please be gentle ;)

As the title suggests, I have both a 2002 model Yamaha 30CV (on a custom centre console Allycraft 410 Rhino) and a 1998 model Yamaha 8hp (on either a 285 Zodiac or old Quintrex 11 footer). I've had the 30CV since new and the 8hp is recently aquired.

When I run the 30, I notice the telltale is not particularly strong, it increases a bit with the revs but overall is not a strong flow. It's been the same since new for what it's worth, and the engine has never been run in sandy/shallow conditions (all paint still intact on skeg and prop as evidence). The flow seems adequate (motor has never overheated etc.) and remains cool to the touch but is just weak. It has been thoroughly flushed with muffs after each and every outing.

The 8hp on the other hand has the strongest telltale flow I think I've seen, hurts the hand if you hold it there for a while kind of strong. This motor has not been particularly well looked after (lots of shallow water running) and as such, I needed to pull the water covers off the head and scrape out all the solidified salt and sand from the galleries. One head cover needed to be replaced due to corrosion, as well as all 3 gastkets, thermostat and collar (not to mention the bolt I snapped in the head that I had to drill out >:( ). The actual head had no corrosion and once put back together runs well.

Additionally the impellor on the 30 was just replaced as part of major service by Yamaha dealer but the 8 was changed who knows how long ago (on the to do list).

Can anyone tell me why the new (well less than 100 hrs) well looked after 30CV has a much weaker telltale flow than the neglected 8? The only thing I can think of is a difference in design. From what I understand the 30CV is an old Mariner 25/30 design that Yamaha have just kept manufacturing albeit with a few improvements here and there.

Thanks for any suggestions in advance.

Gav

[Mac_Attack]

Hi all, first post so please be gentle ;)

As the title suggests, I have both a 2002 model Yamaha 30CV (on a custom centre console Allycraft 410 Rhino) and a 1998 model Yamaha 8hp (on either a 285 Zodiac or old Quintrex 11 footer). I've had the 30CV since new and the 8hp is recently aquired.

When I run the 30, I notice the telltale is not particularly strong, it increases a bit with the revs but overall is not a strong flow. It's been the same since new for what it's worth, and the engine has never been run in sandy/shallow conditions (all paint still intact on skeg and prop as evidence). The flow seems adequate (motor has never overheated etc.) and remains cool to the touch but is just weak. It has been thoroughly flushed with muffs after each and every outing.

The 8hp on the other hand has the strongest telltale flow I think I've seen, hurts the hand if you hold it there for a while kind of strong. This motor has not been particularly well looked after (lots of shallow water running) and as such, I needed to pull the water covers off the head and scrape out all the solidified salt and sand from the galleries. One head cover needed to be replaced due to corrosion, as well as all 3 gastkets, thermostat and collar (not to mention the bolt I snapped in the head that I had to drill out >:( ). The actual head had no corrosion and once put back together runs well.

Additionally the impellor on the 30 was just replaced as part of major service by Yamaha dealer but the 8 was changed who knows how long ago (on the to do list).

Can anyone tell me why the new (well less than 100 hrs) well looked after 30CV has a much weaker telltale flow than the neglected 8? The only thing I can think of is a difference in design. From what I understand the 30CV is an old Mariner 25/30 design that Yamaha have just kept manufacturing albeit with a few improvements here and there.

Thanks for any suggestions in advance.

Gav

Hey Gav first off welcome to ausfish!!!
I have a couple of reasons this maybe be happening.
1. You are so use to your 8hp tell tail ripping your hand off that the 30 seems slow?
2. Water pump may be playing up?
3. I have a 25 hp tohatsu with the restrictor removed its identical to the mercury 30 and the tel tail is week at idle but as soon as she is on the plain you feel it and its very strong.?
4. Just adjust the idle screw next to the carby and have the engine running at a little higher rpm (do this while the engine is running at idle).
Don't worry Gav its nuthing major mine was the same but you just fix the idle and ur fine ;)
Hope that helped if you need help with adjusting the screw just tell us and i can upload some pics.
Cheers Nick 8-)

[Ally410]

Thanks for the welcome and input Nick, nice one.

Yeah you could be right re comparing the two making it more noticable, however I've owned the 30 a lot longer than the 8 and I've always thought it a bit weak but didn't worry too much as all seemed well (and still does at the end of the day).

There shouldn't be any problem with the impellor as it's new (replaced 6 months ago) and there didn't seem to be a noticable change from old to new in the telltale strength.

I'll have a little play with the idle and see what that difference that makes. She does idle well though as is. Being centre console I haven't felt the telltale pressure whilst underway, looking at it though it looks definitely stronger whilst underway but still not a well formed stream as comes out of the 8. Next time I'm out I'll have a check whilst travelling at higher revs.

Thanks again Nick for the input, greatly appreciated.

Gav