1990 190HP 4.3 chevy Mercruiser

[jpw]

I have a 22 foot Marlin Chinook and the boat feels like it is a little underpowered and i am wondering if there is an inexpensive way to increase the HP by around 50 or so with out replacing the Engine.

[fishkisser]

Nope ...

[MattPark]

The correct prop can make a world of difference. Depending on where you are at now RPM wise, maybe you can drop in pitch? Switch to stainless?

[Herring Problem]

The expense to add 30 hp is not worth it. You would be better off to buy a new crate small block v-8.

My trophy has the v-6 and yet if you were to buy this boat in Europe it comes with a 305 chevy v-8. We can't get it here in the us.

But I have seen the conversion and it does make a really big difference.

You would spend about

$ 6000 to convert.

Maybe a bigger boat would work better.

[deepsix]

I have a similar boat. A 22' 93 marlin sport fisher. I have the same engine with a weber 4 barrel. I have run a 15p, 17p and 21p prop on the boat. The 15 seems pretty good for ocean conditions. I like the 17 and the 21 for flat water lake conditions. I have been able to reach recommended WOT of 4800rpm with all of those props under those conditions. The boat also seems to have plenty of power. What prop are you running? It can make a world of difference.

[jpw]

I run a 16p prop and at WOT i get 4100 rpm and 20mph. I also was wondering if any one knows the changes they made to get up to 260hp out of the same eng.

[MattPark]

There were a few marine 4.3s that were 225ish horse, but even the 2009 models are still 190hp. I don't know what heads your engine has, but a set of Vortec heads and an aftermarket intake manifold could possibly give you a little bump in power.

It sounds to me like something is wrong with your engine. Your WOT rpm should be 4400-4800. You are at the low end of props available as far as pitch goes, but your rpm and mph are still too low. I would think you top speed should at least be in the low 30s, and it shouldn't feel underpowered like deepsix noted. It could also be a slipping hub in the prop, but if that were the case your rpm should be much higher.

I would check compression and timing. Does the engine run smoothly otherwise?

[1sast]

Originally Posted by jpw

I run a 16p prop and at WOT i get 4100 rpm and 20mph. I also was wondering if any one knows the changes they made to get up to 260hp out of the same eng.

I have the fuel injected 4.3 in my 2003 19 foot North River. When I first got the boat I quickly found that it felt very underpowered. After a few different prop changes I have found one that gives the best hole shot and top end. I run right at about 40mph WOT@ about 4800 rpm.

[jpw]

Originally Posted by MattPark

There were a few marine 4.3s that were 225ish horse, but even the 2009 models are still 190hp. I don't know what heads your engine has, but a set of Vortec heads and an aftermarket intake manifold could possibly give you a little bump in power.

It sounds to me like something is wrong with your engine. Your WOT rpm should be 4400-4800. You are at the low end of props available as far as pitch goes, but your rpm and mph are still too low. I would think you top speed should at least be in the low 30s, and it shouldn't feel underpowered like deepsix noted. It could also be a slipping hub in the prop, but if that were the case your rpm should be much higher.

I would check compression and timing. Does the engine run smoothly otherwise?

During the pre purchase inspection ( early this year) the compression was OK and the timing was OK. I double checked the timing again again myself and it was right on. The engine runs and idles smoothly. I just don't know what else to look for. Maybe i will go try a couple o different props.Thanks for the input.

[deepsix]

JPW,
Have you checked your boats wieght? You could have a situation where you have absorbed water into foam and stringers. This can add up to several hundred pounds. That would also affect your performance and ability to reach the correct WOT RPM. Just a thought!

[jpw]

Originally Posted by MattPark

There were a few marine 4.3s that were 225ish horse, but even the 2009 models are still 190hp. I don't know what heads your engine has, but a set of Vortec heads and an aftermarket intake manifold could possibly give you a little bump in power.

It sounds to me like something is wrong with your engine. Your WOT rpm should be 4400-4800. You are at the low end of props available as far as pitch goes, but your rpm and mph are still too low. I would think you top speed should at least be in the low 30s, and it shouldn't feel underpowered like deepsix noted. It could also be a slipping hub in the prop, but if that were the case your rpm should be much higher.

I would check compression and timing. Does the engine run smoothly otherwise?

Were would I go to find some Vortec Heads and the aftermarket intake manifold?

[jpw]

Originally Posted by deepsix

JPW,
Have you checked your boats wieght? You could have a situation where you have absorbed water into foam and stringers. This can add up to several hundred pounds. That would also affect your performance and ability to reach the correct WOT RPM. Just a thought!

The Boat and trailer is right at #5000 but i don't know what the weight is w/out the trailer and don't know what the Boat weight should be. I don't have any books/manuals and i believe that the company that build them is not in business any more.

[MattPark]

I have a feeling you already have the heads. They come on S10 Blazers, Jimmys, etc. They are 190 horse as well.

You can find intake manifolds from many different vendors online. I don't think you need a marine specific unit, if they even exist.

I think theres another issue.

[Herring Problem]

Here something to check,
You post the motor is a 1990 4.3 190HP.

From 1990 to 1998, some of the 4.3 v6 were rated from1 60 hp up to 190HP.with 2 bbl carbs.

I am wondering, just by chance could you possibly have a lower rated HP engine, and 16 inch prop is at the higher end of your power scale which would be a reason you can only get 4100 rpms.

2nd. idea is the motor has a electronic modle that regulates the power output of the engine. Also controls the rpm range to protect the engine from over reving. If the engine has a burnt valve or a bad piston, just maybe your power loss is from here.

A couple of thoughts here