I need a 7hp marine engine....any help?

Hi guys, I'm fresh to the model engine scene, I'm after a 6.5 - 7.5hp (more would be great) marine engine that is easy to start and compact.

I have seen the zenoah g260 and the size of this engine is suitable for my application, i'm not making a boat but just need to find the best compact marine engine and you guys seem to know quite a bit about them.

Any suggestions would be much appreciated.

thanks

Our inertial dyno tests put a stock Zenoah at a little under 4 hp at 12,000 to 13,500 rpm, the best modified Zenoahs at slightly over 6 hp at between 15,000 and 17,000 rpm, and the M&D cast cylinder Zenoah at close to 6 1/2 hp between 16,000 and 18,000 rpm. Our early Quickdraw tests show about 7 hp between 17,000 to 19,000 rpm. The engine was seriously upgraded since that time and I believe our best SAW engine developed around 8 hp, but we did not test it. Quickdraw publishes horsepower ratings on their web site.

The Zenoahs were all tested with the same M&D pipe while the Quickdraws were first tested with the M&D pipe and then the Quickdraw hot pipe when it was developed. While the Zenoahs are pretty consistent from engine to engine from the same builder, the Quickdraws had significant engine to engine variation. Our dyno is NOT calibrated and has shown slightly lower power than other builder's tests on the same engine. This data comes from many tests done since 2003.

Lohring Miller

May we ask,what are you building and needing a marine engine with that horsepower,if not in a boat?Something unique or out of the box?

Those water cooled engines are for the boats....
A little update for the M&D cast engine, I got a Dyno sheet from Matt in March this year when I listed my name in the order list, it showed around 7.25 HP at 18k RPM and 6 HP at 19K RPM.

For what kind of application , you could get 7 absolutely useless horsepower:ohmy:

ken0276 wrote:

Those water cooled engines are for the boats....
A little update for the M&D cast engine, I got a Dyno sheet from Matt in March this year when I listed my name in the order list, it showed around 7.25 HP at 18k RPM and 6 HP at 19K RPM.

Lot of good hyping an engine none but a few can even get

The dyno wars so many get drawn into is just silly, Big HP numbers are great for a drag boat, oval running is not the same.

As I said earlier, our dyno is not calibrated and reads lower than other dynos testing the same engine. We do have comparison data from around 1000 test runs on lots of engine, pipe, carb, fuel, oil, and other combinations. We also have historical data that shows engine improvements over the years. The relative readings are the most important.

Lohring Miller

lohring wrote:

Our inertial dyno tests put a stock Zenoah at a little under 4 hp at 12,000 to 13,500 rpm, the best modified Zenoahs at slightly over 6 hp at between 15,000 and 17,000 rpm, and the M&D cast cylinder Zenoah at close to 6 1/2 hp between 16,000 and 18,000 rpm. Our early Quickdraw tests show about 7 hp between 17,000 to 19,000 rpm. The engine was seriously upgraded since that time and I believe our best SAW engine developed around 8 hp, but we did not test it. Quickdraw publishes horsepower ratings on their web site.

The Zenoahs were all tested with the same M&D pipe while the Quickdraws were first tested with the M&D pipe and then the Quickdraw hot pipe when it was developed. While the Zenoahs are pretty consistent from engine to engine from the same builder, the Quickdraws had significant engine to engine variation. Our dyno is NOT calibrated and has shown slightly lower power than other builder's tests on the same engine. This data comes from many tests done since 2003.

Lohring Miller

Lohring,
Your information is dead on. I have had almost the same exact results as you posted on my dyno. A stock Zenoah at a little under 4 hp at 12,000 to 13,500 rpm, My modified Zenoahs at slightly over 6 hp at between 15,000 and 17,000 rpm, and the M&D cast cylinder Zenoah at close to 6 1/2 hp between 16,000 and 18,000 rpm. I have also had the Quickdraw High Rev with all the bells and whistles tests show about alittle over 7 hp between 17,000 to 19,000 rpm and the new RCMK EVO engine make 4.89.

The biggest problem in my opinion is some of the more popular dynos not being properly calibrated. I can not tell you how many 6-1/2 to 7-1/2 horsepower modified engines with dyno sheets I have had at the shop that would barely make 5.7 hp on my dyno. Some of the guys using this stuff are advertising 6 to 7+hp Zenoah engines to make sales. I have found in my testing that these results have been on average of 1-1/2HP higher then in my opinion they should be. I have never had any Zenoah from anyone and I have tested a lot of them ever make that kind of power on my dyno. The engine we used in the S.A.W. boat to set the IMPBA and NAMBA record made 6.3hp but would overrev to 24,000 and has some very trick machined parts.

I know we could write pages and pages of who's dyno is accurate and who's is not accurate. If you have a dyno and you do not change anything from pull to pull and the results are different it is not doing any good as you do not know what changes are helping or hurting. I have owned and still own most of the popular ones out there and keep going back to the inertia dyno with Performance Trends Software. It is in my opinion the most accurate and repeatable system for checking our little engines.

I often hear a lot of times that the dyno means nothing and results show on the water. Well that is true, but I have never shown positive results on the dyno that has not shown positive results on the water. Most of the time those comments are made by guys that are selling engines to the public that do not have a dyno. When we test our main concern is not with peak horsepower numbers but more towards a broad and usable hp/torque curve. That is what helps win heat races and not make them so picky about what props will work. There is no way to make small changes to an engine and test on the water to verify results accurately. If guys are trying to sell you stuff and that is there means of testing then beware. There are way to many variables in water conditions and boat setups to ever really get accurate results. In my opinion having a good dyno is a invaluable tool to any engine modifier.

If you are looking for a true 7hp marine engine then my suggestion would be a Quickdraw High Rev engine with modified WYK33carb and whatever else Quickdraw recommends to go with it or a Quickdraw 35cc engine.

These are only my opinions.

ya a quickdraw 35 or the new cmb26

You need 7hp? Don't we all!:boredom:
Cya Graeme