dory 11ft and yamaha 9.9hp

[QBhoy]

Hi

I don't mean the plate on the boat.
As mentioned in my last post, there should be a plate on the engine bracket that attaches to the boat.

 

[polotche]

Ok sorry
I posted ? picture of this plate just before

 

[polotche]

I find a 9 1/4 x 7 propeller cheap
Do you think it s a good choice?

 

[Sea Rider]

I find a 9 1/4 x 7 propeller cheap
Do you think it s a good choice?

Without taching current 9 prop to check its max wot rpm achieved impossible to tell which less pitch prop OB needs, could be a 8-7 pitch wild guess. With how many boaters do you usually boat with, are 8-7 props and an induction tach available locally, need to import ithem ?

Happy Boating

 

[polotche]

I usually sailing with friend fisher that's all or all alone

The propeller come from France and it's a new item, about 70 usd

I will order and try it

 

[Sea Rider]

Definitely should plane combo faster, but won't know for sure if OB runs passing max wot range which could be dangerous for internal rotating parts. Not knowing max wot rpm achieved with current 9 and going for 7 less pitch, OB could achieve as much as + 500 wot revs increase per one less pitch, so theoretical +1000 wot revs with a 7 prop.

Would advise to get an induction tach along that 7 pitch prop. A prop mximization done right could save money if going for a 15 HP conversion.

Happy Boating

 

[polotche]

Ok I understand, I am looking that up for tach...

My offer for propeller has been refused so I'll wait a little longer and in order to see if you can have the parts to convert my yamaha

Many thanks

 

[Sea Rider]

Mathieu,

[FONT=&quot]There's a french dealer : [/FONT]Karl Stice at kastice@wanadoo.fr sells Tiny Tach Hour/Tachs model TT2A, contact him. Install a tach meter, follow instruction to the letter before going for a higher HP upgrade. Less pitch props can do miracles while boating solo or with 2 up.

Happy Boating

 

[polotche]

Hi,
Thanks sea rider for your answer
I buy a tach but not a tiny because I prefered to keep some money for something else. So I buy a china tach come from France, that should do
I receive it this weekend, I would make a try

many thanks

 

[Sea Rider]

The tach that you bought has firing sequence programmable mode ? some tachs don't have this nice feature and could read half or double max wot rpm due to being fixed tachs not compatible with OB firing. Has happened to me....

Happy Boating

 

[polotche]

Yes, the tach is for 2 or 4 stroke with the possibility to adjust the number of sparks

 

[Sea Rider]

OK way to go, install tach, go for a wot run lightly loaded and report max wot rpm achieved preferably on flat calm, no wind water cond..

Happy Boating

 

[polotche]

Ok, I'll try this Sunday I will tell you Thanks

 

[polotche]

Hi,
I try my boat yesterday with the tach and my yamaha take 4000 rotations

I also drill the hull and there is water

I don't known what to do, Help me

Thanks

 

[Sea Rider]

Firstly need to drain all that water water inside hull, water is quite heavy. Where was water flow passing under lower leg, the video shows a great deal of water outside transom, there should be a near flat middle wake outward transom. If flow is hitting over upper water def plate OB will lose rpm due to water drag and excess water volume outside transom. Check by visual inspection.

Less water on hull and a correct OB/transom height will pull wot revs higher, how much, impossible to know, a new water test needs to be done. Anyway 4 K wot revs is way low, at the extreme lugging side of OB...

Happy Boating

 

[polotche]

Ok thanks sea rider, I understand
you think I have to go up or down the engine??

How much the maximum rpm for this engine??

Thanks

 

[Sea Rider]

If too much water is lodgged on hull and depending on its weight could make hull, transom and OB to sit further down and water flow at speed to pass above upper plate when needs to pass under. This will make middle wake exiting rear lower leg to havea higher water amount circling when needs to be a near flat undisturbed outing wake. Check.

https://www.youtube.com/watch?v=oBeZjaA76VM

Being a clamp OB see if can rise it slight bit higher with wooden shims unde swivel bracket till outter wake flattens more as in the posted link example. Report your findings..

Being an oldie OB, don't have at hand their factory stated min-max wot rpm range. Modern 2 stroke Yams usually runs 5000-55000 wot rpm.

Happy Boating

 

[polotche]

Hi,
Ok, I will mount the engine and repeat tests
I have some repairs before

 

[QBhoy]

I thought there might be water in there. Famous for it.
Is the engine a short or long shaft ? Should be a short or standard on that boat.
Defo doesn't sound like it is giving the full beans anyway. What prop is on it and have you checked the compression ?

 

[QBhoy]

Just saw you posted earlier about the prop.