V-Hull Engine Height without NC/WP

[oks81]

Hello!

Wonder how high outboard can be mounted on V-Hull without losing coolingwater, without using waterpickup nor nosecone.
Any who has an idea?

I have tried to search the forum but could not quite get an good answer.

Looking at picture of Winrace used in GT30 it seems like propeller shaft is pretty close to the bottom of the hull.




Maybe shaft about 1" lower then the bottom of hull is safe?

[KIRCHNER]

I USED to run a stock 15'' merc lower, on a 20'' transom, no cone,no lwp, no problems.

[oks81]

I USED to run a stock 15'' merc lower, on a 20'' transom, no cone,no lwp, no problems.

Thanks for reply!
Can I ask what size was your Merc.?

[KIRCHNER]

IN-LINE 110, chopper prop.

[oks81]

In line is nice, chopper is good!

Had this setup before. Was with waterpickup.




Yamaha got sick... so it`s sold.
Try to make some plans for the future. Meanwhile I use 9,9hp for fishing.

[Jimboat]

Wonder how high outboard can be mounted on V-Hull without losing coolingwater, without using waterpickup nor nosecone. Looking at picture of Winrace used in GT30 it seems like propeller shaft is pretty close to the bottom of the hull.

Suggest that you install a water pressure gage, so that you know just where you are. The max engine height while still getting safe cooling water supply will depend alot on the hull bottom design and setup, and varies with speed, and also affected when cornering, so there really isn't a 'rule of thumb' for a 'safe height'. With a pressure gage, it's easy to play with the engine height and keep a close monitor of water supply. it's easy to see when you've gone too high with a gage, and expensive to find out the hard way!

[oks81]

Thanks for reply!

I think you are both correct.

Either go mounting with propeller shaft safe distanse under the hull, or use pressure gauge if go really high.

[rgsauger]

I watch my pressure gauge more than my tach. You need one. You can also add the little side scoops on your lower to help catch and funnel water in when running higher. They do work

[oks81]

Maybe a little of topic but...
Bought a new propeller for my 2-stroke 9,9hp Yamaha with lower pitch.
But I think I maybe got a little bit to low pitch, rpm sounds high.

The boat is nice to run with this propeller so want to keep it, is it ok maybe compensate high rpm with a little more oil mix?
This is done in racing?

[rgsauger]

Yep. Done every day. We use 50:1 up to 6,000 rpm. Then 40:1 up to 8k or do.

[oks81]

Thanks I just go for 1:50.
The Yamaha is specced for 1:100.

[rgsauger]

You are more than covered at 50:1 and could probably run 80:1 and have a little more protection than the 100:1. No need to double oil unless you are breaking in a motor.

[oks81]

Think you are correct.
At the same time, think producers of these old 2 stroke engines made them to handle some high rpm.
There is no rev limiter, and how many do actually use time to fit the correct propeller and measure rpm?

Forgot to mention, it is actually 15hp, have removed the throttle limiter and opened the reed stopers to 6mm.