70 HP vs 85 HP on pontoon boat

[djwalters]

I have a 24' pontoon boat with a mid 80's 70HP Johnson for power that I would like to get a little more top end speed out of. I found a mid 70's 85HP Johnson with only 120 original hours. Motor is in great shape, but is it worth the time to change for only 15HP? Any problems with the older 85HP engine vs the newer 70HP one? Neither motor has electric shift which I know can be problems. Thanks so much, Dave

 

[rickdb1boat]

Re: 70 HP vs 85 HP on pontoon boat

Hi DJ,<br /><br />At best you will be looking at a couple miles an hour improvement. I too have a 91' 70 Rude on my toon and it does fine. If you were talking about something over 100 horses, then maybe. But I would have to pass on the 85, unless of course, it's one of those deals that are just too good to pass up...BTW-Those 70 HP motors are extremely reliable, as you probably know....

 

[waterinthefuel]

Re: 70 HP vs 85 HP on pontoon boat

We have a 24' barge with an early 80's Evinrude. I doubt the 85 would help much, not to mention with 4 bangers, it's going to burn a lot more fuel. You can't beat those old 70's.<br /><br />How do you know it's only got 120 original hours on it?

 

[phatmanmike]

Re: 70 HP vs 85 HP on pontoon boat

How do you know it's only got 120 original hours on it?

duh... you scan the engines E-prom. sheesh! <br /><br /><br />

 

[djwalters]

Re: 70 HP vs 85 HP on pontoon boat

Thanks for the info guys, I was kind of thinking the same thing. Not worth the time and effort. The 85HP is still on a parts boat I purchased that a tree fell on. Boat is all original and hour meter reads 120 hours. From the looks of the boat / motor, ( before tree encounter )I'd say hours are accurate. Thanks again, Dave

 

[CFronzek]

Re: 70 HP vs 85 HP on pontoon boat

Pontoon boats a strange animals. They don't have much surface on the water so they are probably displacement hulls. If they don't plane that means anything beyond displacement speed will only be achieved with applications of enormous amounts of power. Read "gas guzzling" in to that.<br />Displacement speeds (about 10mph for a 24 footer) can probably be had with 25-30 HP. <br />The rule of thumb for driving a displacement hull beyond hull speed is that it take a doubling of HP for each 1 mph increase over hull speed. <br />Go slow and save gas. Give your motor a break.