rpm ranges

[coolguy147]

would a older 59 10hp be more powerful then a 9.9 mercury 4 stroke or yamy 9.9 2 stroke

well my motor i believe if right makes 10hp at 4000rpm not bad? but the recommended rpm range is 4500 so it would make 10 and a half or 11hp? not sure what rpm its running on my 20ft pontoon but sounds like its getting there.

but i see the merc saying 5000-6000 rpm range again four stroke and a yamy 2 stroke going for 4500-6000rpm i mean y? i know the newer motors r measured at the prop so what? is mine more powerful? but how much less or more?

 

[tashasdaddy]

Re: rpm ranges

your is measured at the power head, new one prop. they are close.

 

[F_R]

Re: rpm ranges

There is more to it than a simple answer will serve. The second main issue is torque. And at what rpm is the maximum torque developed? These stats are rarely published. Your old 10 develops a lot of torque at relatively low rpm. Rev that old baby up to 6000 rpm and it probably will actually push the boat slower. Until it beats the wrist pins out of the pistons. Which is not uncommon in the 10.

 

[coolguy147]

Re: rpm ranges

but there is also another question that came to my mind. fuel consumption . would this thing get good fuel eco since it runs at lower rpms? or is 10hp 10hp? so since its an older motor it will burn like 1 1/2 -2 gallons of gas in an hour at wide open the little sucker literally lol.


and i have this on a 20ft pontoon basically nothing on it but i believe its a heavy load for this motor right? since i assume its already proped correctly for a pontoon would i have to change this for my john boat? would love the easy manuveriblity and speed on it. wasnt sure about this? not sure of the specs of the prop right now and rpm on my motor so ya... how can i check rpm without installing a big high tech tach and the trouble. would this item be usuable on other motors also?

 

[pvanv]

Re: rpm ranges

The Merc 9.9 4-stroke is actually a re-badged Tohatsu/Nissan 9.8 "in sheep's clothing". As a Tohatsu dealer and mechanic, as well as owner of a new Nissan 9.8, I can say that the WOT fuel consumption is 1.0 gph or less. See http://www.tohatsu.com/tech_info/fuel_consumpt.html for the factory fuel economy data.

My 9.8 replaced a mid-70's 'rude 15, and actually has better low-end thrust, and much better reverse that the old 2-stroker. But a lot of that is due to correct (high-thrust 4-blade) propping for my sailboat. The 9.8 spins up to 6,000 with no issue at all, but as was said previously, I would keep your old 10 down below 5,000 so it doesn't beat itself apart. Indeed the power and torque curves are different between these 2 motors, with your old 10 probably making more torque at low rpms. The new 4-stroker, being measured at the prop, should have a hair more (maybe 9%) maximum output. If you prop correctly to exploit that power, you should be fine.

Do you want to use it in a high-load setup, such as the pontoon boat, or on your light jon boat? Two completely different setups, so you would definitely want different props for the different applications.

 

[coolguy147]

Re: rpm ranges

awwwww man crap thats going to set me back on my john boat project....

where can i get a new prop? how much? can it be through prop exhaust will it work?

so to be sure im proped correctly where can i get a rpm thing to check my rpms? hopely all this time ive been running at about 4500rpm.


hey i just thought of something since my motor has really good torque at low end. i would be the new 9.9 motors beat em in the hole shot? plus my motor only weighs like 70 pounds theres like 80-100

 

[pvanv]

Re: rpm ranges

You can get a cheap digital tach at http://www.cabelas.com/cabelas/en/t...240401&cm_ite=0015240015383a&_requestid=11748

The Tohatsu/Nissan 8/9.8 weighs 86 pounds, and is through-hub exhaust.

 

[coolguy147]

Re: rpm ranges

well i was looking through my garage and found a portable tach meter made by stewart warner. now this thing was old!! kinda i guess. i learned that u put it on the nut on the flywheel and press and it spins. only problem is that the thing only goes up 3500 rpm so ya... but i am curious what my motor idles at


i will check the local lawnmower shop since the ones form napa cost like 100-200 dollars

 

[coolguy147]

Re: rpm ranges

really there through hub exhaust?!?!? i thought everyone went to through prop. which one is better may i ask? performance differences?

oh and my guess was right u know i did say 80-100 pounds
but if i want a different motor on my pontoon i would like to find something less than 130-150 pounds anything maybe a 25-40 hp range most likely if i get a newer motor it will be a 25hp at most since the weight and older ones 30-40hp.


can u give me the weight of some of the older 30-40hp rnages like the 2 cylinder motors

 

[steelespike]

Re: rpm ranges

You can get a tinytach,reasonable,easy install,and can be used on any similar motor without regard to stator poles.Just be sure you tell them what you need as you need to have the proper length wire.Can't splice wire.

 

[coolguy147]

Re: rpm ranges

yup 2moro the snapper shop is open so ill see what they have for a reasonable price.



can u give me the weight of those motors i asked for though?