Upgraded the pontoon!

[calvinator]

I had a 60hp on my 30' pontoon. Gave me a whopping 10mph last year. Kids want to go tubing ! ! Last year I set out to upgrade the motor. Also wanted a tow bar for easier hookups.

Spent a lot of time figuring out what will work, measure, measure, trial fits, etc etc. My pontoon is 90 minutes away, so that added to complexity. Here are some pics!

New, old motor.... 1975 Merc 1500 Tower of Power... 150hp. 319 hours!



At home, I fixed her up. Runs perfectly....




Blank canvas ...



Loaded my Suburban with all the gear....



Engine hoist made moving the 350lb motor easy....

 

[calvinator]

Re: Upgraded the pontoon!

Motor on.....






Tow bar installed... Can't see it, but tow bar mounted to 1/2" steel plates.... nice 'n sturdy !





A few more days until launch! 30' pontoon definitely won't be carving the waves, but I'm just looking for 20-24mph straightline to pull the tubes with !

Bad news.... that motor is a gas guzzler, but sounds MEAN.... Worth it in my book ! ! !

 

[The Rooster]

Re: Upgraded the pontoon!

Nice work Calvin. I'm guessing you've added approx. 150 #'s to the transom. Any additional bracing? Looking forward to seeing your new speeds. Good luck !!!

 

[chrismarion]

Re: Upgraded the pontoon!

I too, would like to know. I have a 24 foot with a 40hp Mercury and want to put on my 115hp in its place. However, my engine pod looks to be similar to yours and it is only connected to two cross members. I am positive two cross members is not strong enough for a 115hp. Weight and torque I think are too much for the factory engine pod from those days.

 

[calvinator]

Thanks -

My transom pod is really beefy. This pontoon is a 1990 Crest III Sundecker and rated for a 125hp motor. The transom is some thick aluminum and is gusseted. Where the motor through-bolt mounts, there are two 2"x3" aluminum boxed cross braces. Transom pod is attached to 5 braces with 10-1/2" bolts on the underside. The first and last brace are the 2"x3" boxed braces.

I also have a picture when this pontoon was new. It had a 125hp Evinrude hanging off the back.

I'm feeling good my transom pod is ready for this motor. I did walk around the marina storage lot and looked at other pontoon transom. Mine is nice and beefy!

I launch in a week -- I'll report back how she performs !

 

[MaPaHa]

Calvinator,

Your last post is helpful. I've been watching this thread and like several others I was concerned about the transom based on the pictures. It looks like it's hanging out there a ways from the last major cross member without a lot of support. It's good to know it's rated at 125 HP and I know what you've got with the 2x3 square tube cross braces where the bolts are. I'd just have someone drive the boat and watch the whole motor / transom under load.

Anytime someone changes a 60 HP to a 150 HP, guys like myself that look at structure raise an eyebrow and look closely. It sounds like you've looked it over pretty well but it doesn't show everything that you're seeing in the pictures so some of us were concerned.

I like those Mercury in-line 6 cyl motors. My brother and I each had a 115 of the same vintage for many years and lots of good memories on the lake with them. I got where I could keep it running good once I learned the motor. I would suggest running a regular treatment of Yamaha "Ring Free" in the gas. It helps keep the compression up and the carbs working good. I had a slightly weak cylinder and it would goof up one carb because of a low vacuum at idle, which would throw off the other cylinder on that carb. In essence one weak cylinder would cause the motor to bog down when taking off. Once you got some rpm's up it was fine. Other than that, the only real trouble I had was I lost a timing belt on the lake because of the bearings in the distributor locked up and broke the belt.

Let us know how it runs

Mark

 

[calvinator]

Had the shake down test. Mixed results.

I don't have a trailer, the marina launches and retrieves me. Well, launch day there was a trailer problem and I had a 4 hr delay. grrrrr.

Launched the toon, motor started right up. Into reverse, and things went well. Got past the no wake zone, and I throttled up. All good, I was at 18mph in no time! Went to 24mph and it was a stable, windy ride! All smiles. I never made it to WOT

Went through the no wake zone at 1500RPM and all was great.

Headed back to dock and then had some troubles. Motor would die at idle shifting gears. Wouldn't stay running below 1000-1200 RPM. It was a rough docking event, but no damage. So I have some homework to do for fixing my die-in-idle problem.

Also, the 15p prop has to go. Doesn't move the pontoon at slow speeds. I found a 10p on clearance, so that is on its way ! !

Going to be a blast working on the pontoon in the water. There is little room to work !

A few more tweaks and summer looks fun !

 

[MaPaHa]

Yea I know what you're dealing with trying to go from idle (fast idle) to getting it in gear without it dying. Try running some power-tune through the carbs and you can find out which one is giving trouble. When spraying it in the carbs with it running, the carbs that cause the engine to lose the most rpm's is the strongest ones. The one that doesn't make much of difference is the weak one. If you have a timing light you can clamp around each wire and see if the light pulse is consistent. Get a spark tester for less than 15 bucks and pull one wire at a time (with the engine off) and set the spark gap at least 7/16 inch. Re start the engine and watch each spark for a hot consistent spark. I did a 77 Evinrude 140 today and every cylinder is firing hot and strong. This eliminates the ignition system.

As I mentioned before, this was my biggest problem with mine and my brothers 70's model 115 Mercury. I would do the power tune cleaning and I would also run a "shock treatment" of the yamaha ring-free in the gas and then back off to regular dose (plus a little). Those engines (carbs) are sensitive with weak vacuums caused by weak compression. Non ethanol gas will help also. You may get lucky and find a carb messing up. I still like those motors, too many good memories.

Good luck

 

[trout74]

love the look of those old motors!

 

[calvinator]

Just some final updates and pictures for any Mercury 1500 inline fans...

I have this thing dialed in now. The motor was dying in idle. I suspected the idle screws on the carbs needed attention, because I was probably running too lean on the idle mix.. I spent 4 hours fooling with them the other day. All the web research and service manuals say start 2 turns out from lightly seated, and then turn clockwise. Clockwise leans the mix, counter clockwise richens the mix.

I was having no luck at all. I took a break, grabbed an Oreo ice cream bar at the marina, and then started thinking that maybe the 1500 Merc I have needs a real rich mix. Went back to the boat and in 45 mins had this baby idling in gear at 800RPM and 900 RPM out of gear. She won't go any lower! A trustworthy and low speed idle was the goal, and I made it. Whew!

For what it is worth to any future searchers, my Mercury 1500 idle screws were set like this:
Top Carb - 3 turns out from seated.
Middle Carb - 2.5 turns out from seated.
Bottom Carb - 2.5 turns out from seated.

Then I took it for a run. I went from 800RPM idle and punched it. Merc roared all the way to 5200RPM with a 15p prop on this 30' pontoon. That is within spec in the service manual for this pontoon and prop combo. 30 MPH on the GPS.

My mission has been accomplished!!! Thanks all for the pointers!!!!

 

[crb478]

Glad you got it dialed in. Pushing a 30 foot pontoon to 30 mph is quite a feat with a 150.

 

[Bamaman1]

Ah, nothing like the smell of pre-mix outboard motor oil in a vintage era engine. And those 150's were really the thing in the mid 1970's. Nothing would run with them until Mercury came out with their Black Max 175 hp.