Bottom boat repair - coatings, and size of engine to install in a 25' Cabin Cruiser?

gggalis

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Mar 13, 2013
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We just got a 25' Searay daycruiser with no engine in it and its been sitting in salt water. The boat weight is 4700 lbs and originally came with a 260HP 5.7liter mercruiser.
We have a 3.0liter 135HP mercruiser, the question is if we install it, will it move the boat? even upriver? any thoughts appreciated.
Second question is how and what is the best way to repair or recoat the bottom of the boat, some places where it hit rocks? you can see the fiberglass.
 

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spoilsofwar

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Re: Bottom boat repair - coatings, and size of engine to install in a 25' Cabin Cruis

Will it move the boat? Yes... at hull speed. It would never plane it.

You should not install that engine unless you are a masochist..
 

25thmustang

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Re: Bottom boat repair - coatings, and size of engine to install in a 25' Cabin Cruis

With the price of used engines, I would lean towards selling the 3.0 and looking for a 5.0 or 5.7. The outdrive gear ratio will most likely be incorrect, but you can pick one up reasonably priced.

Hard to see on my phone but that bottom photo doesn't look like raw glass but down through the gelcoat.
 

gggalis

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Re: Bottom boat repair - coatings, and size of engine to install in a 25' Cabin Cruis

Well I had to loo up hull speed and its a formula 1.34 times the square root of the "speed-length ratio", that will take me a while to figure out.....

I also had to look up Masochism: a sexual perversion characterized by pleasure in being subjected to pain or humiliation especially by a love object. Very intresting in tying that to the boat, but that is why I asked, and I am listening.

As for the 3.0 we have the full set including ourdrive, and on the boat the motor and the outdrive is gone, so we need both.
Is there something wrong with a boat if it doesn't plane? just cruise?
 

tpenfield

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Re: Bottom boat repair - coatings, and size of engine to install in a 25' Cabin Cruis

It *might* get up on plane under ideal conditions . . . it should break hull speed, which is about 7 mph for that boat. (I know that from my sailboat days). No way to tell for sure until you try it. So, you will make headway upriver, but you racing days are over with that engine.

For the knicks on the hull, etc . . . a gelcoat repair kit would do the trick. then maybe a fresh coat of bottom paint for cosmetic purposes.
 

Chris1956

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Re: Bottom boat repair - coatings, and size of engine to install in a 25' Cabin Cruis

Those kind of boats are routinely sold with 305 CU IN SBC blocks. They are dogs, but will plane, if everyone moves to the bow (or into the cabin). A 5.7L motor is a better choice, but you might consider a big block, as that would be ideal.
 

smokeonthewater

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Re: Bottom boat repair - coatings, and size of engine to install in a 25' Cabin Cruis

I have to disagree with the masses here....I have some first hand experience on this... while I cannot GUARANTEE it will plane, I think it is quite likely.
I had a 26' Carver santa Cruz. That is a 5,500 lb (dry) boat with a flybridge , full cabin, and a 115 gallon fuel tank. I had 4 group 31 batteries on board and plenty of random stuff at all times.

My boat came with a 260 as well and the motor lost oil pressure on me so I pulled it and installed a merc 165 inline 6... I had to change the prop a couple times but when I got it right it would plane off very quickly and cruise nicely in the low 20's.... cruise was at 3/4 throttle instead of half and no speed records were set but I enjoyed the boat a LOT and honestly really miss it.

I wouldn't go out and buy such a small engine for your boat but since you already own it, drop it in and get the right prop on it and give her a go..... on your other question as long as you are in sheltered water, sure if all you can do is hull speed (about 7 mph) that is fine... just idle around but I think there is a pretty good chance if the engine is in good condition with the right prop of being able to plane the boat. either way you could get quite a bit of use out of it while you wait for the right deal on a bigger motor.

My current boat had twin merc 260's in it and tops out about 48 mph... I have found similar and larger boats with twin 4 cylinders that don't run near as fast but do plane out and run nicely.
 

25thmustang

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Re: Bottom boat repair - coatings, and size of engine to install in a 25' Cabin Cruis

Smoke, you mean 26' and 5,500 lbs?

A 165 mercruiser ran that boat at 20 mph. That's impressive. I had a 27'er with twin 190s. Couldn't imagine a single 165 in it.
 

smokeonthewater

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Re: Bottom boat repair - coatings, and size of engine to install in a 25' Cabin Cruis

Smoke, you mean 26' and 5,500 lbs?

A 165 mercruiser ran that boat at 20 mph. That's impressive. I had a 27'er with twin 190s. Couldn't imagine a single 165 in it.

yeah... I only WISH I had owned a 36' Carver... would have never sold it.... but yeah 26'er .... NOBODY thought it would run that well including me but I needed an engine in her and a buddy had a rotten out tri hull with this one in it so what the heck we tried it. Really the only issue I had other than top speed was that with the lighter engine the boat seemed tippier when driving from the flybridge and turning hard.

keep in mind, my 2667 was only an 8' beam boat... your 27 was likely a 10' beam and a LOT more boat
 

greenbush future

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Re: Bottom boat repair - coatings, and size of engine to install in a 25' Cabin Cruis

Under powered boats are no fun to be in, drive around in, and they will never sell quick. My 24 footer had a small v8 and it was a heavy boat. It sucked to get up on plane in any type of chop, conditions needed to be almost perfect just to get this tub moving. I ended up selling it to an old man who didn't care about going 20-25 mph.
But you do have a complete set up just sitting there, so if mechanically inclined, drop that baby in and see if you are satisfied. I will be willing to bet, you will yank the baby, and go get the 5.7 you need to push that thing around well. When given the choice on power, almost everyone agree's it's nice to have extra, as opposed to not enough. I been told this all my boating life!
 

gggalis

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Re: Bottom boat repair - coatings, and size of engine to install in a 25' Cabin Cruis

Well thanks guys for the replies, its always better to think outloud, and consider others experiences to try and prevent "boat masochistsm".
The only experience I had with underpower was driving a 3/4 ton pickup that had a 350 chevy loaded with crushed rock up a steep hill, and it bogged down from 55 to 20 mph, but I figured there are no hills on the water.

I will look around and see if I can find a V8 and outdrive.

As for the chipping on the bottom, I will look into gel coat repair kit, but there are so many polymers, epoxies, materials, its taking time to research them out.
 

smokeonthewater

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Re: Bottom boat repair - coatings, and size of engine to install in a 25' Cabin Cruis

Well thanks guys for the replies, its always better to think outloud, and consider others experiences to try and prevent "boat masochistsm".
The only experience I had with underpower was driving a 3/4 ton pickup that had a 350 chevy loaded with crushed rock up a steep hill, and it bogged down from 55 to 20 mph, but I figured there are no hills on the water.

I will look around and see if I can find a V8 and outdrive.

As for the chipping on the bottom, I will look into gel coat repair kit, but there are so many polymers, epoxies, materials, its taking time to research them out.

actually EVERYWHERE you go in the water IS uphill if you are trying to do more than about idle speed... driving the boat with the small engine would be very much like driving that truck up the hill all day long in second gear..... IF you can source a bigger engine you will get much better performance but if you just want to be floating on the cheap you could probably plane with it.... wouldn't be fast by any means tho
 

frantically relaxing

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Re: Bottom boat repair - coatings, and size of engine to install in a 25' Cabin Cruis

I've never heard anyone complain their boat is over powered. ;)

Heh heh-- I have--

See the Sea Ray in my signature? We sold it to some friends, the original engine fired while hydrolocked a month later (head gasket) and busted the block. Friend picked up a 4-bolt truck engine and got thru the summer. That winter he pulled it and had it built into an over-healthy 383. Getting on plane was real easy, but too much throttle would ventilate the prop. He got the boat to 58 mph more than once- which is a feat with a deep-V hulled midcabin- and always had plenty of throttle left, but every time he pushed it for more he spun the prop hub. After 4 props, he bought a 28" pitch solid hub cleaver prop. Even with all the grunt it was a bear to get on plane. But he got it over 60 a couple of times, but not many before melting down the coupler hub. And the meltdowns came with another price, the over-revving broke a cylinder wall twice- he sleeved the first one, the second one cost the whole motor.

We ended up getting the boat back sans motor, and it now has a very low hour silver colored 1984 OMC 5.7 with a bunch of contrasting black Mercruiser parts that pushes her around very nicely...


So yeah, you CAN have too much power! :) And for what it's worth, during all the abuse, the original u-jointed Gen-1 Alpha One handled all that power without issue...

and oh yeah-- Put that 3.0 in that boat with a 15" pitch prop, and she'll get on plane! Might get all of 24 or 25 mph out of her, but I'd bet a buck it would get on plane. (ok, with trim tabs at least!) ;)
 

Solittle

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Re: Bottom boat repair - coatings, and size of engine to install in a 25' Cabin Cruis

I had a 27'er with a 350 & it was a slug. Go for a big block.
 

Maclin

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Re: Bottom boat repair - coatings, and size of engine to install in a 25' Cabin Cruis

If you mean just installing the 3.0 engine with the same drive, then the ratio will be way far off, hate to even think what that little engine would be going thru.
 

smokeonthewater

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Re: Bottom boat repair - coatings, and size of engine to install in a 25' Cabin Cruis

he said he has the 3.0 and it's correct drive from a donor boat
 

gggalis

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Re: Bottom boat repair - coatings, and size of engine to install in a 25' Cabin Cruis

Ok, I got the boat up in the air, sanded the bottom, and sprayed Gelcoat with black coloring, surface hardener, and catalyst, and its curing now.
They say the gelcoat is not waterproof enough on the bottom of boats to prevent hydrolysis, so my next step should be which one of these:

1. Let gelcoat cure at least 12 hours then spray with a polyurethane clear coat?

2.Let gelcoat cure at least 12 hours then roll or spray an enamel based trailer paint (I have black color) ?

Which one will stick better to the gelcoat? is 12 hours enough for gelcoat to dry? Which one will protect best/last longest?
 

JoLin

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Re: Bottom boat repair - coatings, and size of engine to install in a 25' Cabin Cruis

You put a lot of work into this- why not just use a marine-specific barrier coat, like Interlux?
 
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