Enough horsepower?

[BrianVT]

I've got a 1993 Hurricane deck boat that's 17'6" and 1,670 lbs.
It has a 2-stroke 70hp outboard on it. It will plane with 2 people on board but not with 3.
It can take up to 140hp.
I have a chance to trade my 70hp even for a 110hp with a guy that says he wants a smaller engine on his bass boat. Will this be a huge improvement that I'll be happy with or should I hold out for a deal on 140hp. I'm hoping to be able to pull a skier or a tube.

 

[ahicks]

I had a 115 Johnson on a 19' aluminum deck boat for a while. That boat had no trouble pulling about anything!

As far as your boat, is your 70 turning up it's full rated rpm when wide open? If not, depending on how far off it is, that can make a HUGE difference in it's ability to plane out.....

For good performance, the right prop is super important....

 

[BrianVT]

This barge weighs a lot more than aluminum. ;-)
It does sound (to my ear) like I should be getting more RPMs at full throttle. Even when I'm solo and planing. The tach. isn't working so I guess I should buy a hand-held and do some testing to see where I'm at.
But I still think I'm gonna need more HP to be happy.

 

[racerone]

Do a compression test on the 110 HP before you shake hands on a deal !!

 

[BrianVT]

Do a compression test on the 110 HP before you shake hands on a deal !!

Of course. Thank you.
Actually, I won't do the deal unless I get a demo. on his boat. And vice-versa.

 

[jimmbo]

If I remember, the 110 has the Bubbleback Exhaust cover, so for all intensive purposes, it is basically a crank rated 140, but prop rated. The 140 rarely put out more than 128hp at the crank, but that fell the within the10% variance allowed from labeled hp

 

[racerone]

These V-4 motors often have issues with broken piston rings.-----Use due diligence if investing in one.

 

[BrianVT]

I do know how to evaluate and maintain/repair engines.
But I'm new to boating.
Assuming good engines, will I notice a huge difference from 70hp to 110hp to 140hp on a 1,670 lb. tri-hull fiberglass deck boat?

 

[racerone]

Let us know how the deal works out.

 

[BrianVT]

I won't even be bothering with the deal until I have an idea if going from 70hp to 110hp is worth the effort vs waiting for a deal on a 140hp.

 

[racerone]

The 70 HP of 1985 and older was 49 / 50 cubic inches.------The V-4 is 99 / 100 cubic inches.------Amazing power if in good condition.

 

[BrianVT]

They're both 1992-93 2-strokes, fwiw.

 

[racerone]

Good luck with making a deal.

 

[909]

If you get the 110 ... in the back of your mind you'll always want a 140

 

[BrianVT]

If you get the 110 ... in the back of your mind you'll always want a 140

That's my concern.
But if the 110 can pull a (slalom) skier then I'd be content. And will not have had to put out any cash.

 

[jimmbo]

A 110 on 16 ft boat, can pull a Bare Foot Skier, deep water start, no skis

 

[ahicks]

This barge weighs a lot more than aluminum. ;-)
It does sound (to my ear) like I should be getting more RPMs at full throttle. Even when I'm solo and planing. The tach. isn't working so I guess I should buy a hand-held and do some testing to see where I'm at.
But I still think I'm gonna need more HP to be happy.

A few thoughts. First our 19' alum boat weighed about the same as your "advertised" weight. If your boat is that gutless, there's an issue with the boat being waterlogged, or the motor is down on power (for whatever reason e.g. prop issue). If the boat is good to go, power in excess of 100hp should prove pretty lively. If you are being cautious about this new motor plan, weighing your boat to confirm it's condition should be part of your plan. Doing that should be pretty simple, and if it is OK, should go a long way in confirming you're on the right track repowering.

Know that these deck boats, when right, should just pop right up out of the water. They have these big wide nearly flat bottoms that plane out very easily. For that reason, they're usually great for pulling about anything (even on limited power), and they don't ride well in a chop!

 

[BrianVT]

Interesting.
I am also surprised that it doesn't plane easier, being so wide and flat. But this is my 1st boat so I have nothing to compare it to.
It is dry in all the under-deck cavities but I suppose there could be water intrusion somewhere that I'm not aware of and the inner foam could be waterlogged?
I guess I will weigh it the next time I take it out.
Thank you for the insight.

 

[jimmbo]

Myself, I would be putting a 150 on it. If you are worried about exceeding the HP rating, a Merc 135 V6 would be a great choice for that boat.

 

[harringtondav]

If someone wants to trade down it is often a sign they have a reason to unload their motor. Do the checks mentioned above. If it is a good motor, go for the swap. You'll be in a better position to upgrade to a higher power O/B if you decide that's what you want.