V4 cross flow upgrade

[bishopcherrycoke]

Hello friends! I just picked up a beautiful old 1974 Glastron Carlson CV 16. Any information anybody has on this boat ie: specs, weight, reviews etc would be greatly appreciated!
My question is this, I have a 1979 evinrude 85 hp cross flow motor I plan on bolting to this boat. The motor is a semi fresh rebuild and runs beautifully! I want to add more power and have heard of guys tinkering with these motors. Mainly because the gears are all rated for 120hp and the power head is the same. (i think) What do I need to do to get more power without compromising reliability? Please note, I have 4 kids and money is tight. Buying a bigger motor is not possible. I'm looking for inexpensive power gains here, if possible. Thanks!

 

[emdsapmgr]

Re: V4 cross flow upgrade

You've got a 99.6 cubic inch powerhead. Scrounge around for a set of 125/135 carbs from the early 70's. They will bolt right on. You may need to rejet them slightly, as they are likely to overfuel somewhat at higher rpm's. You'll get 3-5 hp by adding four rubber intake filler blocks(322684) from a 79 140. These have long since gone NLA, but you can still find them in marine teardown shops. Your current heads are good for about 125 lbs compression-not bad at all. A set from an early 140 will give you even more (maybe 10 lbs.) If you want to tear the block down, you can enlarge the intake/compression ports. Work on your setup-that's usually free hp: make sure you run a stainless prop and mount the engine high enoughon the transom to reduce drag, but not so high that it runs out of cooling water. Prop the engine to run 5700 or 5800 after your mods.

 

[kenmyfam]

Re: V4 cross flow upgrade

The cheapest way to get optimum performance is to have the set up just right. Motor height, trim, weight distribution of crew and gear and of course the optimum prop for the outfit.
Is it possible to get more HP out of it.....yes but you could spend a fair amount of money in the process. Make sure as well you do not exceed the max HP for the boat whatever that is.
Personaly I would do the above first before considering anything else.
Just my personal opinion though.
Good luck with the new boat.

 

[bishopcherrycoke]

Re: V4 cross flow upgrade

So far I have been able to find a carb and a bible back exhaust manifold. Will that bubble back help at all?

 

[bishopcherrycoke]

Re: V4 cross flow upgrade

Also, will a stainless steel prop really make a difference over aluminum? I run the boat in the chain o lakes in northern IL. Very shallow lakes with Many shallow channels. It makes me nervous to use one.

 

[emdsapmgr]

Re: V4 cross flow upgrade

I would not waste my $ on a stainless prop in the Fox Lake area this summer. The water there is normally very shallow and this summer it has been even lower. If you hit anything, stainless props are close to $200 for repairs. Having said that, you can run a stainless prop with a higher engine mounting than almost any aluminum. Less engine in the water=less drag=more speed.

 

[boobie]

Re: V4 cross flow upgrade

If the mtr is running good now leave it alone and just keep it tuned good. For the hp you would gain for trying to modify it and the $$$$ spent it's not worth it.

 

[kenmyfam]

Re: V4 cross flow upgrade

If the mtr is running good now leave it alone and just keep it tuned good. For the hp you would gain for trying to modify it and the $$$$ spent it's not worth it.

+1 on the above

 

[bishopcherrycoke]

Re: V4 cross flow upgrade

Roger on the shallow waters on the chain! the motor runs great and it pushes my 16 foot checkmate 44 mph with just me in the boat. The glastron is a bit lighter, I'm sure the numbers will be close to the same. But I like to go fast maybe I'll just save my penny's for a bigger motor down the road.

 

[bishopcherrycoke]

Re: V4 cross flow upgrade

Do you guys think a jack plate would help a smaller motor at all or is that just something for bigger motors? Manual jack plates are relatively inexpensive.