Moving too slowly 9.5 hp, 630lbs, 10ft achilles??

nabiul · 31 August 2015, 03:59

I picked up a 9.5 hp johnson like in the link below and had it out on the water today. I know for a fact the motor was not producing full power, the rpm was unstable and it appears the little plastic cylinder that rides between the timing plate and the throttle lever was missing, but it would be safe to say that we were getting a good 7-8hp.

I'd estimate the total weight of everything including boat and motor to be around 630lbs and it looked like we were moving less than 10km/h. The motor appeared to be doing a lot of splashing around instead of pushing; the wake was huge compared to some similar boats that appeared to be moving faster. I do not think the boat picked up on a plane either, instead the bow was always pointing about 10 degrees out of the water at full throttle.

I want to know what is wrong with my setup, the max this boat is rated for is 10 hp so it would be kind of ridiculous if it could not plane with a 9.5hp motor. The cavitation plate sat about 1 or 2 inches under the water when not moving if that is important.

The motor model
http://sportfishermans-service.com/w...4/IMG_3445.jpg

The boat model
http://www.skifflife.com/files/2015/...HV_600x450.jpg

The actual propeller, it's in rough shape and I want to know if it's matched to the motor or not.

http://i.imgur.com/qm0UU7h.jpg

office888 · 31 August 2015, 04:26

I had a 1966 MQ11C (Johnson 9.5) and was easily able to move an Avon 315 Rollaway at about 20 mph... it had about 70 psi of compression left in it.

Sounds like your outboard is broken just like you said? Check the compression too.

nabiul · 31 August 2015, 05:53

How fast would you estimate this boat is moving? I think this is close to what is happening to me.

https://www.youtube.com/watch?v=X6dW-02bPQ4

willk · 31 August 2015, 07:08

Quote:

Originally Posted by nabiul

I picked up a 9.5 hp johnson like in the link below and had it out on the water today. I know for a fact the motor was not producing full power, the rpm was unstable and it appears the little plastic cylinder that rides between the timing plate and the throttle lever was missing, but it would be safe to say that we were getting a good 7-8hp.
I'd estimate the total weight of everything including boat and motor to be around 630lbs and it looked like we were moving less than 10km/h. The motor appeared to be doing a lot of splashing around instead of pushing; the wake was huge compared to some similar boats that appeared to be moving faster. I do not think the boat picked up on a plane either, instead the bow was always pointing about 10 degrees out of the water at full throttle.
I want to know what is wrong with my setup, the max this boat is rated for is 10 hp so it would be kind of ridiculous if it could not plane with a 9.5hp motor. The cavitation plate sat about 1 or 2 inches under the water when not moving if that is important.The actual propeller, it's in rough shape and I want to know if it's matched to the motor or not.

You seem to have your own query well under control!

The engine isn't making power, the prop is scuffed and the boat is overloaded. I'm gonna guess very little of the weight was forward of the centerline as well?

You don't say what equipment and passengers were onboard, or what air pressure was in the boat - it may help us? Were you using a tiller extension?

Poly · 31 August 2015, 07:21

Quote:

Originally Posted by willk

You seem to have your own query well under control!

The engine isn't making power, the prop is scuffed and the boat is overloaded. I'm gonna guess very little of the weight was forward of the centerline as well?

You don't say what equipment and passengers were onboard, or what air pressure was in the boat - it may help us? Were you using a tiller extension?

Nor do you suggest if you tried different trim settings.

You say the ant ventillation plate was below the water when stationary, but how does it compare to the bottom of the hull?

Even when new that engine didn't put out as much HP as a modern 9.5 as the method of measuring it has changed.

ShinyShoe · 31 August 2015, 07:39

You've been given plenty of likely things to look at but while you are looking...

I assume there is either a wooden ridge under the floor or an inflated tube? Just in the photo the V does not look that big...

Secondly could there be any prop slip ? The prop sits on a rubber 'gear' for want of a better description ... If that's damaged it results in surges in revs.

Mikefule · 31 August 2015, 08:34

First thing I'd check is the tilt of the motor. Most motors have a 3 position stop. When I first fitted my outboard I had it on the middle setting. The first time I tried it at full speed it sounded and acted like the clutch was slipping. I worked out that the prop was sucking air in. I dropped the tilt to the lowest setting and now it works fine.

Second thing on any inflatable is to get the weight distribution right. That usually means moving crew and baggage forwards.

nabiul · 31 August 2015, 15:07

Two passengers on board, about 230lbs each; we tried both at back and one at back and one close to the bow. My friends also went out, about 160 at back and maybe 230 right on the bow; they moved quicker but no planing.

We started with a neutral trim and changed to trimmed out which appeared to make us move faster since the bow was climbing so much. The plate was probably level with the bottom of the transom, but the tubes are much lower. How much power would you estimate it to be compared to today? I'm also looking at an old ted williams air cooled single cylinder 7hp motor as a backup since I can't get the 9.5 on the boat by myself.

There is a standard inflatable keel that almost flattens out at the transom. I did not know that the rubber prop holder could slip, it is likely worn out, I will take a look.

It's difficult to have all the weight forwards on such a small boat and each of us weighing so much.

office888 · 31 August 2015, 15:11

Quote:

Originally Posted by nabiul

Two passengers on board, about 230lbs each; we tried both at back and one at back and one close to the bow. My friends also went out, about 160 at back and maybe 230 right on the bow; they moved quicker but no planing.

We started with a neutral trim and changed to trimmed out which appeared to make us move faster since the bow was climbing so much. The plate was probably level with the bottom of the transom, but the tubes are much lower. How much power would you estimate it to be compared to today? I'm also looking at an old ted williams air cooled single cylinder 7hp motor as a backup since I can't get the 9.5 on the boat by myself.

There is a standard inflatable keel that almost flattens out at the transom. I did not know that the rubber prop holder could slip, it is likely worn out, I will take a look.

It's difficult to have all the weight forwards on such a small boat and each of us weighing so much.

Those old Ted Williams engines are junk... I would recommend against it. There's a reason why they sell for $75 - $150.

It should plane with that 9.5 hp. Those old Johnson 9.5hp are awesome.

Check the compression and check your RPMs.

nabiul · 31 August 2015, 15:27

Any specific reasons why they are bad, I've already arranged to meet with the seller? If it is junk then it is being priced like a good johnson or evinrude at $250 (inflated prices in southern ontario).
I was mainly looking at it because of how light it is.

I'm actually getting rid of a 5hp evinrude angler today and sold a johnson hd25 on saturday. I miss the little johnson, so light, idles at low low revs and burned pretty much any mix; I'm looking for something to replace it.

Poly · 31 August 2015, 16:20

Quote:

Originally Posted by nabiul

How much power would you estimate it to be compared to today?

I think it is difficult to say - in days of old the manuf's measured it at the powerhead, whilst today it is measured at the prop, after going through the gearbox. I seem to remember someone suggesting a 10% drop (that it down to 8.5HP, IF it was running perfectly, but its not - so maybe you are actually only getting 7HP out of it...

Quote:

It's difficult to have all the weight forwards on such a small boat and each of us weighing so much.

tiller extension is the way.

If it were me I would

1. Fix the engine problem - its pointless trying anything else until you do.*
2. Load it lightly, and with as much weight forward as you can (perhaps just you and a tiller extension, fuel and anchor).
3. Adjust trim and maybe engine height until happy; you said you trimmed UP - you probably want to be trimming DOWN (moving leg closer to transom) to bring the bow down and help it get over the hump.
4. Get someone to film it - so you are not guessing what it looks like - how it feels inside and outside is often different.
5. Then add more people / kit and see how it handles.

* I'd also want to check you have a sensible prop on there (so you need to know what it is, what the gearbox ratio is, what the recommended revs are, and what max revs your getting, and stick a GPS (phone in a bag) on to see what speed you are getting). If it was last on a 5 tonne sailboat pushing at 6 knots it may not be the right prop to get you on the plane.

ShinyShoe · 31 August 2015, 17:11

That air cooled presumably also was old school horses so not much more than the 5 you just got rid of?

nabiul · 31 August 2015, 17:55

The 5 horse angler I sold was made sometime in the 60's. But yeah I am kind of wary it being a single cylinder engine and it is more than I'd like to pay; more than I paid for the 9.5 horse johnson.

I'll take a look at the motor today and see what I can do for it.

nabiul · 02 September 2015, 00:09

Update: The motor is bad, 60psi compression readings in both cylinders and sparks wont jump a gap more than 1/16".

lightning · 08 September 2015, 19:50

The 9.8 is not a high powered engine. I have one on my SIB and it planes easily two up. We weigh about 300lbs between us and our engine weighs 26lbs, the boat etc maybe another 50lbs. So under 400lbs all up.
But my previous engine (a 6hp) took time to get on the plane.
So if you have a dodgy prop and drive with a faulty 10hp motor it's not gonna plane with over 600lbs to push along lol....

nabiul · 09 September 2015, 00:25

Actually we got it planing! The compression wasn't that low, I just wasn't pulling hard enough, a friend managed 70psi. We swapped out the condensers, filed down the points and reset the timing. Motor ran faster but was still hard starting and wouldn't idle well. An aomci member gave us some seafoam to mix with the fuel, what a difference that made! We were doing 15-16km/h as measured by a dodgy phone app, but we were planing!

lightning · 09 September 2015, 04:22

Great stuff! Glad you got it working better. When you only have 10hp to start with it really needs to be giving it's best to get on the plane.

Nightfisher · 09 September 2015, 09:33

With the motor off, pull the cowl, give it full throttle then hold it. While holding the tiller ensure the throttle at the carb has opened full to the throttle stop. Even at 70PSI per cylinder it seems quite low. Next time do a wet compression test.

While cold, squirt a couple shots of 2 stoke oil into one cylinder at a time and do another test. If the wet-compression test reads above 100PSI and 85 or less on the other..time for a ring job. I'd check the serial number with a sight that can say what the compression should be. All and all it could need, from what your writing, a load of work including rebuilding the carb..installing a nreed valve block... Good Luck.