Engine upgrade

[plamke1949]

I have a 1988 Four Winns 18ft. It has a V6 Volvo Penta and OMC outdrive. I'd like to gain some horsepower by replacing the engine. What engine would go in without having to relocate mounts, etc., etc? Am I better off just replacing the intake, carb and exhaust??

 

[PITBoat]

I have a 1988 Four Winns 18ft. It has a V6 Volvo Penta and OMC outdrive. I'd like to gain some horsepower by replacing the engine. What engine would go in without having to relocate mounts, etc., etc? Am I better off just replacing the intake, carb and exhaust??

I have a 1988 Four Winns 18ft. It has a V6 Volvo Penta and OMC outdrive. I'd like to gain some horsepower by replacing the engine. What engine would go in without having to relocate mounts, etc., etc? Am I better off just replacing the intake, carb and exhaust??

If it works well, I'd leave it alone.

 

[plamke1949]

If it works well, I'd leave it alone.

Thank you for your time. It seems like it doesn't have power. Very hard to get the boat to plane as that the outdrive always has to be down. Attempting trim pulls the nose way up no matter the speed. I am an experienced boat owner but not with this small of craft. My boats have always been 24 to 28' in length with 375 to 500hp. I may have to spend more time operating this boat. It will be used solely on Lake Mohave and Lake Mead and parts of the Colorado River....

 

[hugh g]

Your boat not planing can be caused by a number of factors. It doesn't look like it's underpowered.
Is it tuned up?
How many passengers?
Are you operating the trim properly?
Your boat is waterlogged & carrying too much exces weight from foam that is soaking wet.
What prop are you using?

An 18 ftr. powered by a V-6 should have no proplem planing off, so something's not right.

 

[Lou C]

Agreed the 4.3 is perfect for an 18 foot boat. These boats came with a points distributor that works fine but needs to be maintained. This includes replacing & adjusting the points and cap & rotor and also lubing the mechanical advance weights so they don’t seize up. Then there’s the fuel system, carb, pump and filters. The anti siphon valve on these boats can clog or corrode internally and restrict performance. The only performance upgrades you can do cost money:
Add a 4bbl manifold and carb if it’s a 2bbl
Replace the restrictive one piece manifolds with the center riser Volvo style exhaust.
Also make sure you are propped correctly.

 

[plamke1949]

Thank you all for these awesome tips. I'm following up on every suggestion and I truly appreciate your all your inputs!

 

[PITBoat]

I took the whale tail thing (attwood Hyrdo Stabilizer) off of mine once to see if it was hindering my top speed, and it didn't work well at all without it - harder to plane and squirrelly if I remember right. And full down was the only trim option.

Mine's 19'+, a 2bbl model, has a 14 1/2 x 19 3-blade prop (with some slight dings and that), planes easily, and will do mid-40s GPS.

I feel like it's got a little more that I haven't been able to get out of it for one reason or another (carb, points adjustments not 100% maybe, etc.), since my max RPMs are on the low side of spec (like 43-4400), but I'm pretty happy with that.

 

[plamke1949]

I took the whale tail thing (attwood Hyrdo Stabilizer) off of mine once to see if it was hindering my top speed, and it didn't work well at all without it - harder to plane and squirrelly if I remember right. And full down was the only trim option.

Mine's 19'+, a 2bbl model, has a 14 1/2 x 19 3-blade prop (with some slight dings and that), planes easily, and will do mid-40s GPS.

I feel like it's got a little more that I haven't been able to get out of it for one reason or another (carb, points adjustments not 100% maybe, etc.), since my max RPMs are on the low side of spec (like 43-4400), but I'm pretty happy with that.

Thank you! I'd be very happy with mid 40's, to be sure. I'm thinking about a better 2bbl carb, like a Holley marine. Maybe a Mallory electronic distributor and better exhaust like a blogger suggested. Also thinking about a 5 blade prop.....

 

[PITBoat]

The guys on here that know seem pretty happy with the factory setup for the ignition system (see Lou's post about the points and that above). It's tied in with the shift system and going to electronic could cause some issues with that. It can be done though.

The prop thing is touchy too - too much and you won't be able to get your max RPMs which isn't good for the engine. There are recommendations in the factory service manual.

I've still got the points ignition and a Rochester carb (though some came with a Holley I believe). I was forced to upgrade the exhaust when one of my original manifolds ("batwing" style) caused a mild overheat due to being clogged with rust.

 

[Lou C]

What I'd do is keep the points distributor, the electronic conversions can be more trouble than they are worth if the module fails and you have no spares, just learn how to set points, and lube the advance weights (there is a lubricating wick in the center of the distributor shaft, it just takes a few drops of oil 1x a season. The other option is to upgrade to a Delco EST but then you need to change the ESA module.
If its a 2bbl, get a 4bbl marine intake (these can be found for the older Pre-Vortec) on ebay if you look around, and an Edelbrock 1409 carb
Then get rid of the old OMC one piece batwings (3.5" outlets) and upgrade to the 2 piece 4" exhaust, you can use Barr aftermarket manifolds & elbows, I used Volvo Penta parts to mate the 4" elbow exits to the 3.5" OMC Y pipe.
Without doing major work this is about the most you can do, will give approx 205-210 hp, which should be fine for an 18 foot boat.

 

[plamke1949]

What I'd do is keep the points distributor, the electronic conversions can be more trouble than they are worth if the module fails and you have no spares, just learn how to set points, and lube the advance weights (there is a lubricating wick in the center of the distributor shaft, it just takes a few drops of oil 1x a season. The other option is to upgrade to a Delco EST but then you need to change the ESA module.
If its a 2bbl, get a 4bbl marine intake (these can be found for the older Pre-Vortec) on ebay if you look around, and an Edelbrock 1409 carb
Then get rid of the old OMC one piece batwings (3.5" outlets) and upgrade to the 2 piece 4" exhaust, you can use Barr aftermarket manifolds & elbows, I used Volvo Penta parts to mate the 4" elbow exits to the 3.5" OMC Y pipe.
Without doing major work this is about the most you can do, will give approx 205-210 hp, which should be fine for an 18 foot boat.

This makes sense. I get the electronic ignition issues as well. I'm all about bolt on horsepower, too.....I don't want to add too much HP and have to deal with changing out gear ratios in the outdrive. I'll stick with a better 3-blade as well. Any comment on changing the engine pulleys to aluminum? Thank you so much for helping me!

 

[Scott Danforth]

only thing to replace a 4.3 and not change mount locations is to have a 4.3

service the points and use a dwell meter not just feeler gauges. improper dwell is as bad as improper timing. after you set dwell, go back and set timing

an 18' boat with a 4.3 should fly.

what are your compression numbers?

no need to change exhaust unless you have batwings

are you running on all 6 cylinders?

are the flappers still where they are supposed to be, or did they drop. if they dropped, they will plug the exhaust and the motor wont run right.

 

[Scott Danforth]

This makes sense. I get the electronic ignition issues as well. I'm all about bolt on horsepower, too.....I don't want to add too much HP and have to deal with changing out gear ratios in the outdrive. I'll stick with a better 3-blade as well. Any comment on changing the engine pulleys to aluminum? Thank you so much for helping me!

you cant bolt on much hp on a properly running 4.3.

changing to vortec heads will add 20-30hp. adding a 4-barrel will add another 10hp.

most hp you can ever get is 240hp at the flywheel (about 220hp at the prop)

the 4.3 is on the edge of reversion due to the engine design, so you can not gain much with a cam change if you leave the wet exhaust. only other option is a blower and dry exhaust (jacketed and runs out the transom), then you can run a jet motor cam. however at the price to build that motor you could have bought a much newer boat with a much better drive and a much larger motor.

 

[Bondo]

Thank you! I'd be very happy with mid 40's, to be sure. I'm thinking about a better 2bbl carb, like a Holley marine. Maybe a Mallory electronic distributor and better exhaust like a blogger suggested. Also thinking about a 5 blade prop.....

Ayuh,...... Welcome Aboard,......Another 2bbl. carb,..... is Still a 2bbl. carb,....
A 4bbl. carb will give ya a noticeable boost in top-end, not so much down low
As Scott is tellin' ya, the Vortec head swap, with a proper manifold, 'n 4bbl. carb is a worth while swap,.....
Beyond that is V-8 territory,....

Readin' yer story, I believe you need to atleast, tune the carb for the altitude, 'n drop a couple inches of prop pitch,..... Don't waste yer money on a 5 blade prop,....
Stick with a 3 blade inexpensive aluminum, til ya get the pitch dialed in,......

 

[plamke1949]

only thing to replace a 4.3 and not change mount locations is to have a 4.3

service the points and use a dwell meter not just feeler gauges. improper dwell is as bad as improper timing. after you set dwell, go back and set timing

an 18' boat with a 4.3 should fly.

what are your compression numbers?

no need to change exhaust unless you have batwings

are you running on all 6 cylinders?

are the flappers still where they are supposed to be, or did they drop. if they dropped, they will plug the exhaust and the motor wont run right.

Thank you!! Holy fright! I've got work to do!.