What pitch 420 mercury

[Tellum]

Hi all, curious what prop people are using on there 420 ocean runners. As mentioned in previous post I have a 420 with new 30hp tohatsu on the back.
I find that I am hitting the rev limiter more often then not, mostly around 24 knots depending on conditions tide flow wind etc. It still leaves me with about a quarter of throttle lever un used.
The prop on the engine is a 9.9x12, it's always a light-ish setup me at 75 kilos 22ltr of fuel and fishing gear.
I have no rev dail, so hoping someone runs a similar setup without hitting the rev limiter, and knowing what prop they use.
I can always back off the power, but I don't light the engine reving more then it needs to for any given speed.

[harrison]

Worth taking a gander here methinks. Exact same question discussed in some detail.

viewtopic.php?f=6&t=3694

[Tellum]

Thanks for the link Harrison, rang Bridger where I got the setup , they said could possibly go to a 14 pitch but couldn't get one for up to 6 weeks. 13 pitch could suffice,especially on those rare occasions when I have 3 aboard. Then just back off when lightly loaded.
A bit of luck ,just found a 9.9x13 pitch hardley used 35 quid, so a cheap test, might do the job .

[harrison]

Sounds like a plan.

Deffo recommend getting a small induction tach, virtually impossible to determine most efficient prop size without and also useful for logging running hours.

Personally don't mind running slightly under propped and having the ability to bounce off the rev limiter lightly loaded as prefer good hole shot over ultimate top speed.

Whatever prop you fit make sure the motor can reach its recommended max rev range (5250-6250) at wot when typically loaded.

[sonny1]

hi @Tellum ive just part exed my ocean runner 420 and tohatsu 30 and this is a subject close to my heart as i had the same ,,,,,reluctant to say problem ,,,,occurance with my set up and it drove me mad. i spoke to all and sundry about it and to be honest i arrived at the conclusion ,after collating all the advice i got,that if the warning light/buzzer activates, just back off the revs a little. as it was explained to me, with the prop you have ,and i cant remember what mine was, your hitting the rev limiter now but if you go out fully loaded you probably wont hit it. if you stay at WOT with warning activated the motor will go into limp home mode . it could be that im talking rubbish but that is how i think it was explained to me. i did like the tohatsu with a big multifunction tiller and would have the tohatsu again , if only for the warranty. a friend of mine had one with the very same situation occuring. the company that supplied mine advised me not to mess about with it.

[Tellum]

I have found a used 13pitch prop so I will try that, I will have a spare prop if nothing else. I will also buy a small tach, any recommendations, there are a few out there for not to much money. A 13 pitch prop new ,although not original equipment is around 55 quid. Is it worth paying for an original tohatsu prop when I work out the best for my setup?

[sonny1]

i would always go oe,personally

[ChrisParish]

If your engine is in warrantee then go oe. If not then do with what fits your wallet.

[Tellum]

Its got to be oe really engine only 6 months old and it might effect the warranty if I don't. Thank you all.

[Tellum]

Is there a way to distinguse between a oem prop and a copy. My 2nd hand prop as arrived for me to try before a buy a new genuine one, but how do I know if the 2nd hand one I bought is not a genuine one, is there a serial number on the genuine prop. I had a look on my genuine prop on the engine and I cannot see much difference only the date is stamped on the genuine one,but not on the 2nd one I have just bought.