'76 Holiday i/o 18' Fishing Rebuild (pic heavy!)

[mickyryan]

Dont feel bad i have a broke skeg on this outdrive i picked up so you arent alone, put a sticker next to key to remind you

 

[italianstal27]

Well we're really stuck now...

We're trying to figure out how to attach that corner trim piece to the boat. Before, there were 10 small screws into the transom. We'd like to avoid that... We're currently thinking a 1" x 1" piece of angled aluminum, 1 rivet on the far ends of the stern cap. That would give us enough room to rivet into metal. Before riveting, we would lay a thick bead of 4200 on the underside of the aluminum to provide some sealing from rain, etc. running down the back of the transom.

How did everyone else install this last piece of trim? It's a doozie!

-John

 

[Watermann]

The end caps were attached by blind rivets on my boats.

 

[italianstal27]

Back to working on the 'ol girl. Our fish finder started doing weird stuff so we took the plunge and got a lawrence with gps woop woop!

We also threw on trim tabs, and boy is that a whooping. So the previous owners had drilled 18 small holes where the port trim tab now resides. Covering these with starboard was the best idea we had. Unfortunately that also meant the trim tabs were pushed out 1/4", both the bottom hinge and the top 3 bolts.

Since we unfortunately have our deck almost touching the transom, it was darn near impossible to reach down far enough to thread the bolts. We didn't want to trust sheet metal screws to hold the tabs. Closed end rivets are an option, but after much deliberation we decided on #10 bolts with washers on the back end with copious amounts of 5200.

Word from the wise: install trim tabs before your deck goes in. With 2 of us working, it took almost 4.5 hours to get these installed.

5200 gets everywhere. I mean EVERYWHERE. have multiple pairs of gloves available, paper towels, and brake cleaner / acetone for cleanup.




So because of lack of access, we had to mount the tabs 3/4" above the bottom of the boat. We'll let you know how well this works, or if it introduces significant problems. Our hope is that they will get out of the way enough once on plane. We do lose 1/4" of metal plate sitting still.

Also note the 1" hole we had to drill through the transom for the new fishfinder. That'll get a second coat of epoxy tonight.

 

[Watermann]

I like those Bennett tabs, which model did you get?

You can get a clam shell to cover that gaping hole in the transom that looks good.

 

[italianstal27]

the 10"
model# SLT10

Did you end up leaving your tabs in the middle position or did you go with the "most lift"

 

[Watermann]

I left them mid point, seems to give the best lift without pushing the bow down too much.

 

[italianstal27]

Last week when Wyatt took the boat out, things went bad. After putting the boat in gear and being underway for 2-3 minutes, he suddenly lost the ability to throttle back the engine. He actually couldn't move the throttle at all. So he killed the engine and spent the rest of the day with the kicker. We took the throttle apart last night and I think we've discovered why things weren't working anymore

Should've taken watermann's advice and replaced the cable when we first did the rebuild

 

[italianstal27]

That boat in the background may or may not be getting it's own thread soon

 

[Watermann]

Yeah new cables are cheap insurance, I just replaced a set along with new controls on a friends 1965 Holiday with a 3.0L.

 

[italianstal27]

Boat is back after getting a boot for the canvas. We're going to try transporting the boat this way. The small hole was patched with HH-66 cement. Goal is to keep the canvas from rubbing on the windshield, or get some soft material between the two. Trim tab 5200 is now hard and the fishfinder wiring is done.

We're taking her out next Saturday for the first trip with the trim tabs!!!! Hopefully she'll handle better!

 

[strokendiesel002]

Looks good! Can't wait to hear about the results!

 

[italianstal27]

Well, we didn't let the boat slide down the boat ramp this time
and!! We were on a boat! So that's cool right? And we didn't lose or break any gear!

So the trim tabs probably work. They kept the bow rise down tremendously. However, the engine won't rev over 2000 rpm in gear. We suspect it's either a cylinder not firing (due to excessive vibrations). We burned almost 10 gallons of fuel traveling 3 miles.

There was also a spring that the previous owners had to help pull the throttle tight against the choke can. That spring has actually been interfering with the choke causing the boat to "semi-choke" itself when the RPMs get high enough.

Given that the engine oil looks "sooty" we are now thinking a carb cleaning is in order. Compression test. And check spark plugs for an overly sooty condition causing a "no-spark".

​​​​​​I know old cars don't like to sit. How often is everyone running their 1970s Merc 120-140s?

 

[italianstal27]

The "smart" trim tabs worked flawlessly!

we replaced the smart plugs and she fired right up We identified that the return spring for the throttle linkage had bound up the carb linkage causing the carb to never come off choke for the 30 minutes we ran the boat back in 2019.

A new oil change and plugs and she is running like a top! Still unable to get past 3700 RPM, but that could be a fuel delivery problem that we also need to sort out.

Unfortunately I drove the boat too quickly through a drift wood pile and snapped the bracket for our brand new fish finder so there's another $48 down the drain.

Here's the video of us finally running the boat at 24mph and catching a springer on the Columbia!!!!!!!

 

[Watermann]

Nice fish guys! Looks like you got the boat going good and the set up working for the salmon :thumb:

 

[italianstal27]

Always progress being made!

We've been hitting a max of 3600 RPM which isn't *terrible* considering it's a mercruiser 120 which the manual says maxes out at 4100.

We thought hey maybe we're getting a little bit of fuel restriction at the top end which is causing us to bog down on the throttle at full pull... So after approximately 60 gallons of fuel and 3 years since the original water fuel separator we pulled it to take a look and.......



Had a little bit of gunk in there! So we throw a new filter on and she definitely needed a choke adjustment because it was gassy and sotty and wow there was a lot of black smoke being thrown out the exhaust lol

Got her all dialed in and she starts very nicely now! Max RPM is still 3600 with top speed of 24 - 25mph (SOG).

We brought two additional people with us (roughly 400 lbs) and our max speed dropped to 20-21mph (SOG).

Our prop is a 14.25x21 3 blade, we're considering moving to a 17P, but really wondering if the juice is worth the squeeze

We'll definitely be keeping up on our maintenance better!
-John

 

[Watermann]

Yeah you have that 120 way over propped with a 21p and that could mean a very short life span. I have a 23p on my 205 HP 4.3 L V6 Chief with a cruise speed of 30 MPH at 3k RPMs. You never want to run an IO at WOT (max RPMs that is) for very long, a few minutes tops so the cruise speed is what's important usually around 3k RPMs.

I would for sure drop to a 19 or 17p for heavier loadouts, it will pull up on plane with little effort and cruise in it's preferred RPM range meaning a longer life for the motor.