Repowering 305 Volvo Penta

"Hi folks. I'm thrilled t

"Hi folks. I'm thrilled to find this board! I have a Wellcraft V-20 and I'm re-powering my 1980 VP marine 305 with a remanufactured long block (my 280 VP outdrive is still in good shape). I'm trying to salvage as much from the old motor as possible, but it is 27 years old, so there is a fair amount of rust on it. I've been able to salvage a few parts and buy some others from a marine recycling yard, but some things I'm obviously going to have to buy new. Any advice I can get to guide me through this process would be greatly appreciated!

To start with, I'd like to replace all of the bolts with new ones. What material should I use to minimize rust and electrolysis? Are there complete kits available for a project like this?

Thanks in advance for your help!"

"Things that you should instal

"Things that you should install brand new include manifolds, risers and fuel pump. Rebuild alernator, starter and carb. Make sure your distributor is tested in a professional shop to make sure the advance curve meets the manufacturer's specs and if it is too worn, replace it (you will be glad you did). Try to install a fresh water cooling package if you can, and install a new thermostat. If the old intake manifold has been raw water cooled, consider renewing it unless it is in excellent condition. Also, renew the bearing and seals in the bellhousing (consider installing a sealed bearing so that you will not have to worry about greasing).

Also, check the condition of the wiring; and if you find it in poor condition, replace it with marine grade wiring (tinned)

Regarding bolts, I suggest regular grade 5 mild steel (plated) and coat the threads with Perfect Seal, OMC Gasket Sealer, or similar.

I may have forgotten something, but that should cover the basics."

"I'd bolt in a 350,.......

"I'd bolt in a 350,........ It'll bolt right Up to the rigging, Same as the 305......

Kinda like Free HorsePower....."

"I agree with Bondo. One of th

"I agree with Bondo. One of the biggest mistakes that, in my opinion, boat owners make is to have an engine that will develop the boat speed they want close to the maximum engine RPM. This won't harm the engine per se, but they will have to rebuild the engine earlier (wear is directly proportional to RPM) and the fuel bills will be significantly higher.

With an engine rated for higher horsepower than what you theoretically need for your boat, you can run it in the economy RPM range and yet get the boat speed you would have obtained with a smaller engine at full RPM. You just have to install a prop with more pitch (and sometimes also with more diameter)."

"Thanks, Pescador, for the hel

"Thanks, Pescador, for the helpful information. I'll take your advice and buy new intake and exhaust manifolds and add fresh-water cooling. I'm also going to buy a new distributor with electronic ignition. Do you agree that this is a good idea?

I already bought a 305 long block. I considered a 350 vortec, but bailed on the plan when I found out about the steps invovled with conversion. This is my first time messing around with engines and I really don't want to screw it up, so an even swap seemed like the safest way to go. This way I can use the same wiring harness, fly wheel, bell housing, etc."

"Cliff, on the outside there a

"Cliff, on the outside there are no visible differences between the 305 and the 350, and all the outer parts are swappable (wiring included). If you could still exchange your 305 with the 350, you would benefit for many years to come even if you are using a 2-barrell carb (350 parts are usually cheaper, as they are more common). Nevertheless, your 20' should fly with your new 305 power plant. In any case, the late 80s and early 90s pre-Vortec 350s have better engineered cylinder heads than their predecessors, which amongst other things have the advantage of a lower fuel consumption. If you decide to go for the 350 block, make sure that if your old block has a 12" flywheel you don't get your new block with a 14", or your bellhousing won't fit and you will also need a new starter.

Installing an electronic distributor is an excellent idea, which in addition of allowing better engine starting will save you a lot of headaches in the future."