Need engine but what size?

[edandq]

I just am finishing up restoring my 1970 Starcraft (aluminum) SS. It is rated for a 85HP and had a 1970 Johnson 85 installed until recently when I gave it to the mechanic to pay for his labor when it still never got fixed! I know weight is an issue but the '85 screamed and want to keep the same power or more. I heard that the newer 70's have the same HP as the older 85's. Is that true? How much more weight can I add and not affect the boat's performance? Any thoughts/suggestions?

 

[JB]

Re: Need engine but what size?

Hi, Edandq.<br /><br />Your old 85 was probably equivalent in hp to a modern 70-80hp and weighed around 300lb.<br /><br />A new Johnson carbed 90 2 stroke is probably the closest thing you can get in overall performance and weight.<br /><br />I think I would look for a well kept JohnnyRude 70 or 75hp three cylinder and expect the weight difference (about 50lb less) to make up for about 5hp.<br /><br />It wouldn't have quite the snap out of the hole that the 85 did, but will use about half as much gas and go as fast or faster at top end.<br /><br />Other good choices in 2 strokes are the Yamaha 70 and 90, Evinrude DFI 75 (quite heavy.<br /><br />In a 4 stroke I am a big fan of the Johnson/Suzuki EFI DF70. A bit heavier than your 85, but a sweet, strong 70hp engine.<br /><br />There are some possibles.<br /><br />I am going to move this to General Outboard, where it should get more attention.<br /><br />Good luck.

 

[Darryl34]

Re: Need engine but what size?

I have a 16' aquastar rated at 85h.p. I have a 115 merc on it,this is the same motor as the 90 & 150 h.p.Merc.If you can handle the extra 50lb or so.Why not,I have had no problems with mine since then.Can squeeze 52 mph out of it.

 

[Bass Runner]

Re: Need engine but what size?

I don't know what the beam is on your boat but I have a 16' Chrysler with a 5' beam (fiberglass) with a 1970 70hp Johnson on it and will really get it with a 13x19 prop. I bet that alum boat of your would fly.

 

[edandq]

Re: Need engine but what size?

Some good thoughts. I've been looking at weights, and they can really differ. It seems to me the suzuki 70 (it's on here for sale) has pretty low weight and is a 4 stoke, but I'm afraid I won't be able to pull a skier any more. Wow, this is frustrating. I'm trying to keep the cost down around $4K or less (well, my wife is

 

[Bass Runner]

Re: Need engine but what size?

I asume your boat is a short shaft low transom, i would try to stay with the 3cyl motors if weight is a concern, You said your boat is rated at 85hp it should handle a v-4 (got rid of the elect shift did ya) If you want a rocket go with a 100hp, just remember the transom and the weight limit build a bigger splash well on the boat if the transom can't handle high horsepower you will ruin the boat.

 

[DJ]

Re: Need engine but what size?

edandq,<br /><br />I am very familar with your boat. The 85 was a rocket on those. It was more than adequate on the 18' SS model Starcrafts also. More than enough for dragging multiple skiers.<br /><br />The John/Zuki 70 (4-stroke) would be a great choice. Propped right, it will easily pull skiers and water toys.<br /><br />If that is out of the picture, a John/Rude 70 would be my second choice. I wouldn't put a 90 on that boat.

 

[edandq]

Re: Need engine but what size?

Yeah, I'm really leaning toward a 70 even though the fun in me says go with a 90. I have installed a new transom on it (since they are as simple as plug and play) and just now have to make a decision. If I put in the 70 4 stroke, I'm thinking installing a long gas tank in the back where the cans used to be and running a filling hole to the top of the back, then I'm like the modern guys.. I just want to be safe, yet still be able to have fun! The Suzuki seems to be leading the pack based on cost/weight.

 

[DJ]

Re: Need engine but what size?

edandq,<br /><br />I do not think you will be unhappy.<br /><br />If your boat has a capacity plate and it says 85 hp. Don't go over.<br /><br />Trust me, when you insure this thing, they will ask you what the max hp capacity is. If you tell them 85 and it has a 90, they may not insure you. You'll also have many interesting conversations with the water law.<br /><br />Put the 70 on and enjoy having almost as much power and using half the fuel.

 

[Bass Runner]

Re: Need engine but what size?

Suzuki may lead the field in weight and cost but I think I would lean toward one that will last a long time and run like the wind. Johnny rude all the way.

 

[manitoba1]

Re: Need engine but what size?

edandq:<br />I have the DF70 on a Alumacraft Classic 16 fishing boat but even loaded with 3 batteries I can put a large adult slalom skier out no problem.<br />This motor has great torque and acceleration. Probably a 17pitch prop should work for you and works great on my engine. This engine runs super smooth and quiet. No dissapointments.