Prop hell. 70 HP Evinrude 2 sroke 3cyl.

[Wile E Coyote]

Been going in circles for a while now. Short of selling boat, some tips would be great. Have a Driver 440 speedboat. Would say a semi deep V. 16' long. 70HP Evinrude 2 stroke 3 cyl. +/- 1994.<br />When I bought the rig, had a 13" x 14" pitch aluminum 3 blade prop. Seems original. Problem with this prop is WOT, RPM way too high. Seems to have enough power though, although hangs in the water forever when trying to get a skier out of the water and feels like it's going over backwards at times. Tried weighting the nose, helps, but awful ride, have to play with the trim all the time. Next, tried a ProPulse 4 blade adjustable pitch prop. 13" x 16-20" pitch. Maybe a bit over the top from 14" pitch, but I thought the 70HP would get the boat going at least. With 3 or 4 people in the boat, the motor dies. Won't even get the boat moving. Motor OK. All three cylinders above average compression. Had a major service 6 months ago. New hoses, gaskets, filters etc. Any suggestions............PLEASE.

 

[Biggles]

Re: Prop hell. 70 HP Evinrude 2 sroke 3cyl.

I,m no expert but I would suggest trying a 11" pitch prop. The other two you've tried are a bit on the high side I think for an engine thats going to have to work hard pulling skier and pushing a 16' speed boat along.

 

[Wile E Coyote]

Re: Prop hell. 70 HP Evinrude 2 sroke 3cyl.

Hope I am not annoying anyone by posting this in the Merc/Mariner section. Used to own 2 Merc's. Did'nt see any other relevant prop problem section.

 

[JB]

Re: Prop hell. 70 HP Evinrude 2 sroke 3cyl.

You will have better luck in the JohnnyRude Forum, Wil E.

 

[ob]

Re: Prop hell. 70 HP Evinrude 2 sroke 3cyl.

Your rig sounds underpropped.Do you have a tach aboard? That engine needs to be propped for 6000 rpm /wot with a light load.I'm guesing a 13 3/8 X 17 will put you where you need to be.I recommend installing a omc prop.Only a water test by tach results can confirm final selection.

 

[LubeDude]

Re: Prop hell. 70 HP Evinrude 2 sroke 3cyl.

OB is righ on in asking about if you have a tach, your imfomation means very little to us with out the RPM information. If you dont have one, get one, its the most important guage on your boat.<br /><br />You mentioned "Playing with the trim", Do you have power trim, or are you just messing with the trim pin. Almost sounds like you have the pin in a location other than all the way towards the transom.

 

[R.Johnson]

Re: Prop hell. 70 HP Evinrude 2 sroke 3cyl.

I am not familiar with the boat you are running, but if it is a 16 ft. semi-V performance boat, you are probably way under powered with a 70 HP motor. I have a 15.5 ft. Checkmate. I know I could'nt put four people in the boat, and pull a water skier with a 70 HP engine. I don't care what size prop you would put on it.

 

[LubeDude]

Re: Prop hell. 70 HP Evinrude 2 sroke 3cyl.

Actually a 70 HP should do the job decently if trimmed and propped right.

 

[CaptainPuget]

Re: Prop hell. 70 HP Evinrude 2 sroke 3cyl.

Ditch the 4 blade adjustable. You should be able to run a 19” pitch 3-blade, if you boat a lot with 4 people on board a 17” pitch would probably be better. 14” is too low. The 70hp should push a light 16’ boat to about 40mph.

 

[Wile E Coyote]

Re: Prop hell. 70 HP Evinrude 2 sroke 3cyl.

I'll try to get all the answers here so help will be easier. I have Tacho, at the moment with the 14" pitch, at WOT the RPM is way too high, creeps up to 7000 quickly. I have never run it like that for long, it's just on pull off I open up full to get out then throttle back. Boat is probably 15 1/2'. Not heavy at all. When pulling a skier, only two people in the boat. Joy riding, three. Back seat too small for two people to be comfortable. Only tried the 4 blade adjustable a couple of times. No good for much. I have a couple of pic's of boat to give an idea of shape and size if that will help at all. Thanks for all the replies so far. Trim is have power trim and pin is right at the transom. Even tried shimming the motor forward more. Do'nt know if motor and hull are a bad combo. Last boat I had ran like a dream with a 50HP Mercury. Put a 65HP Suzuki on and it was a disaster. Not too unhappy with this boat, just feel it could maybe perform a little better with some TLC. I feel it should also get out the water a little faster.

 

[Wile E Coyote]

Re: Prop hell. 70 HP Evinrude 2 sroke 3cyl.

One other thing. Seems to burn a hell of a lot of two stroke. Last service I asked the engineer about this and he said it was fine. I agree rather too much than too little maybe, but when I first start up and leave it warming up at the jetty gettin all the gear together, it,s rather embarasing, a thick cloud of smoke all over. Any tips here?

 

[Dhadley]

Re: Prop hell. 70 HP Evinrude 2 sroke 3cyl.

Lets start with the basics. What brand tach is it? Are you sure its set correctly? If its an OMC / BRP tach it should be set on position 6.

 

[CaptainPuget]

Re: Prop hell. 70 HP Evinrude 2 sroke 3cyl.

I’ll give you a couple of reference points. I have two boats powered by 70hp Johnsons. One is a 17’ Arima, semi-V hull weighs in about 2100lbs. I prop it with a 14”x15” aluminum 3 blade. It tops out at slightly over 6000rpm and about 32mph. It jumps right out of the hole even heavily loaded.<br /><br />Boat #2 is a 1200lb aluminum sled, almost flat bottom. It has a 13 1/4x19” prop and tops out at about 39mph at 5800rpm. Also jumps right out of the hole.<br /><br />I have no doubt that the 14” prop is putting you way over the 6000rpm red line. <br /><br />As for your oil burning, I’d guess that you have an air leak in the line somewhere. I mix my on.

 

[rayjay]

Re: Prop hell. 70 HP Evinrude 2 sroke 3cyl.

I was going to ask if a larger dia might be just what he needs.

 

[ledgefinder]

Re: Prop hell. 70 HP Evinrude 2 sroke 3cyl.

Something is way off here - you should have NO problem popping up skiers with a 14" pitch prop.<br /><br />Can you please double-check the rpms (as DHadley suggests), and the prop pitch? <br /><br />My first guess was that the hull was waterlogged. But, if you say it ran fine with a Merc 50, I guess it isn't the boat. Could you pull skiers with the Merc 50? <br /><br />If the tach is correct, and you are running 14" pitch, something has to be wrong with the motor.

 

[ob]

Re: Prop hell. 70 HP Evinrude 2 sroke 3cyl.

If that 15 1/2 foot boat weighs any less than my 15 ft Dauntless Whaler ,the rig is underpropped.

 

[walleyehed]

Re: Prop hell. 70 HP Evinrude 2 sroke 3cyl.

If I were him, I'd run FAST.........Let's back up here to DH's question of type of tach and the setting...<br />We can compare boats all day long and it won't help him...I tend to agree with ob on possibly being under-propped, but let's see what the tach situation is first.<br />And just to mess with ob ( )the 13-3/8X17 is an SS in OMC...alum is 13-1/4X17, or 14X17...

 

[ob]

Re: Prop hell. 70 HP Evinrude 2 sroke 3cyl.

Not at all Walleyed. OMC's sstII is what I run.13 3/8 X 17.Also keep a 13X19 OMC sstII prop for those solo outings.I'm also interested to see if the tach is reading right and in the proper setting.If I were to install a 14 " pitch on my rig I would expect to see rpms at WOT in the 7000 range.Mine raps out to 6000 with the 19".I'm also well aware that Dhadley is no dummy.

 

[walleyehed]

Re: Prop hell. 70 HP Evinrude 2 sroke 3cyl.

No insult or bad intended, ob....hope ya didn't take it that way. Sometimes I have a hard time coming across as I wish to...

 

[Wile E Coyote]

Re: Prop hell. 70 HP Evinrude 2 sroke 3cyl.

Not sure of the manufacturer of the Tacho. I know that the RPM is high at WOT. Here's a question. Are there any cheap no name brand aluminum props sold that could give me these symptoms. Like a badly manufactured prop. Just a thought. There are no markings on this prop except 13x14. I also drilled three holes as per the advice of the evinrude manual. No difference. As for pipes leaking etc. Had a major service a little while ago. Reputable Evinrude agent. All new hoses and gaskets and filters. He gave me all the old ones. I know he could have given me any old ones, but I could see on the motor they were new. Compression on all 3 cylinders good. Could someone post a picture of my boat here. You will all be able to see the size of it. I am sure it should perform better than it is.Would love to sort this out before summer. He also changed spark plugs telling me the previous owner had been running the wrong sort. I could feel the difference after the service. Easier starting for one.